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White dwarf

January 10, 2023

For other uses, see White dwarf (disambiguation).
"Degenerate dwarf" redirects here. Not to be confused with Degenerate star.

A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes from the emission of residual thermal energy; no fusion takes place in a white dwarf.[1] The nearest known white dwarf is Sirius B, at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun.[2] The unusual faintness of white dwarfs was first recognized in 1910.[3]: 1  The name white dwarf was coined by Willem Luyten in 1922.

Image of Sirius A and Sirius B taken by the Hubble Space Telescope. Sirius B, which is a white dwarf, can be seen as a faint point of light to the lower left of the much brighter Sirius A.

White dwarfs are thought to be the final evolutionary state of stars whose mass is not high enough to become a neutron star or black hole. This includes over 97% of the other stars in the Milky Way.[4]: §1  After the hydrogen-fusing period of a main-sequence star of low or medium mass ends, such a star will expand to a red giant during which it fuses helium to carbon and oxygen in its core by the triple-alpha process. If a red giant has insufficient mass to generate the core temperatures required to fuse carbon (around 1 billion K), an inert mass of carbon and oxygen will build up at its center. After such a star sheds its outer layers and forms a planetary nebula, it will leave behind a core, which is the remnant white dwarf.[5] Usually, white dwarfs are composed of carbon and oxygen (CO white dwarf). If the mass of the progenitor is between 8 and 10.5 solar masses (M☉), the core temperature will be sufficient to fuse carbon but not neon, in which case an oxygen–neon–magnesium (ONeMg or ONe) white dwarf may form.[6] Stars of very low mass will be unable to fuse helium; hence, a helium white dwarf[7][8] may form by mass loss in binary systems.

The material in a white dwarf no longer undergoes fusion reactions, so the star has no source of energy. As a result, it cannot support itself by the heat generated by fusion against gravitational collapse, but is supported only by electron degeneracy pressure, causing it to be extremely dense. The physics of degeneracy yields a maximum mass for a non-rotating white dwarf, the Chandrasekhar limit — approximately 1.44 times M☉ — beyond which it cannot be supported by electron degeneracy pressure. A carbon–oxygen white dwarf that approaches this mass limit, typically by mass transfer from a companion star, may explode as a type Ia supernova via a process known as carbon detonation;[1][5] SN 1006 is thought to be a famous example.

A white dwarf is very hot when it forms, but because it has no source of energy, it will gradually cool as it radiates its energy away. This means that its radiation, which initially has a high color temperature, will lessen and redden with time. Over a very long time, a white dwarf will cool and its material will begin to crystallize, starting with the core. The star's low temperature means it will no longer emit significant heat or light, and it will become a cold black dwarf.[5] Because the length of time it takes for a white dwarf to reach this state is calculated to be longer than the current age of the known universe (approximately 13.8 billion years),[9] it is thought that no black dwarfs yet exist.[1][4] The oldest known white dwarfs still radiate at temperatures of a few thousand kelvins, which establishes an observational limit on the maximum possible age of the universe.[10]

Discovery

See also: List of white dwarfs

The first white dwarf discovered was in the triple star system of 40 Eridani, which contains the relatively bright main sequence star 40 Eridani A, orbited at a distance by the closer binary system of the white dwarf 40 Eridani B and the main sequence red dwarf 40 Eridani C. The pair 40 Eridani B/C was discovered by William Herschel on 31 January 1783.[11] In 1910, Henry Norris Russell, Edward Charles Pickering and Williamina Fleming discovered that, despite being a dim star, 40 Eridani B was of spectral type A, or white.[12] In 1939, Russell looked back on the discovery:[3]: 1 

I was visiting my friend and generous benefactor, Prof. Edward C. Pickering. With characteristic kindness, he had volunteered to have the spectra observed for all the stars – including comparison stars – which had been observed in the observations for stellar parallax which Hinks and I made at Cambridge, and I discussed. This piece of apparently routine work proved very fruitful – it led to the discovery that all the stars of very faint absolute magnitude were of spectral class M. In conversation on this subject (as I recall it), I asked Pickering about certain other faint stars, not on my list, mentioning in particular 40 Eridani B. Characteristically, he sent a note to the Observatory office and before long the answer came (I think from Mrs. Fleming) that the spectrum of this star was A. I knew enough about it, even in these paleozoic days, to realize at once that there was an extreme inconsistency between what we would then have called "possible" values of the surface brightness and density. I must have shown that I was not only puzzled but crestfallen, at this exception to what looked like a very pretty rule of stellar characteristics; but Pickering smiled upon me, and said: "It is just these exceptions that lead to an advance in our knowledge", and so the white dwarfs entered the realm of study!

The spectral type of 40 Eridani B was officially described in 1914 by Walter Adams.[13]

The white dwarf companion of Sirius, Sirius B, was next to be discovered. During the nineteenth century, positional measurements of some stars became precise enough to measure small changes in their location. Friedrich Bessel used position measurements to determine that the stars Sirius (α Canis Majoris) and Procyon (α Canis Minoris) were changing their positions periodically. In 1844 he predicted that both stars had unseen companions:[14]

If we were to regard Sirius and Procyon as double stars, the change of their motions would not surprise us; we should acknowledge them as necessary, and have only to investigate their amount by observation. But light is no real property of mass. The existence of numberless visible stars can prove nothing against the existence of numberless invisible ones.

Bessel roughly estimated the period of the companion of Sirius to be about half a century;[14] C.A.F. Peters computed an orbit for it in 1851.[15] It was not until 31 January 1862 that Alvan Graham Clark observed a previously unseen star close to Sirius, later identified as the predicted companion.[15] Walter Adams announced in 1915 that he had found the spectrum of Sirius B to be similar to that of Sirius.[16]

In 1917, Adriaan van Maanen discovered van Maanen's Star, an isolated white dwarf.[17] These three white dwarfs, the first discovered, are the so-called classical white dwarfs.[3]: 2  Eventually, many faint white stars were found which had high proper motion, indicating that they could be suspected to be low-luminosity stars close to the Earth, and hence white dwarfs. Willem Luyten appears to have been the first to use the term white dwarf when he examined this class of stars in 1922;[12][18][19][20][21] the term was later popularized by Arthur Stanley Eddington.[12][22] Despite these suspicions, the first non-classical white dwarf was not definitely identified until the 1930s. 18 white dwarfs had been discovered by 1939.[3]: 3  Luyten and others continued to search for white dwarfs in the 1940s. By 1950, over a hundred were known,[23] and by 1999, over 2,000 were known.[24] Since then the Sloan Digital Sky Survey has found over 9,000 white dwarfs, mostly new.[25]

Composition and structure

Although white dwarfs are known with estimated masses as low as 0.17 M☉[26] and as high as 1.33 M☉,[27] the mass distribution is strongly peaked at 0.6 M☉, and the majority lie between 0.5 and 0.7 M☉.[27] The estimated radii of observed white dwarfs are typically 0.8–2% the radius of the Sun;[28] this is comparable to the Earth's radius of approximately 0.9% solar radius. A white dwarf, then, packs mass comparable to the Sun's into a volume that is typically a million times smaller than the Sun's; the average density of matter in a white dwarf must therefore be, very roughly, 1,000,000 times greater than the average density of the Sun, or approximately 106 g/cm3, or 1 tonne per cubic centimetre.[1] A typical white dwarf has a density of between 104 and 107 g/cm3. White dwarfs are composed of one of the densest forms of matter known, surpassed only by other compact stars such as neutron stars, quark stars (hypothetical),[29] and black holes.

White dwarfs were found to be extremely dense soon after their discovery. If a star is in a binary system, as is the case for Sirius B or 40 Eridani B, it is possible to estimate its mass from observations of the binary orbit. This was done for Sirius B by 1910,[30] yielding a mass estimate of 0.94 M☉, which compares well with a more modern estimate of 1.00 M☉.[31] Since hotter bodies radiate more energy than colder ones, a star's surface brightness can be estimated from its effective surface temperature, and that from its spectrum. If the star's distance is known, its absolute luminosity can also be estimated. From the absolute luminosity and distance, the star's surface area and its radius can be calculated. Reasoning of this sort led to the realization, puzzling to astronomers at the time, that due to their relatively high temperature and relatively low absolute luminosity, Sirius B and 40 Eridani B must be very dense. When Ernst Öpik estimated the density of a number of visual binary stars in 1916, he found that 40 Eridani B had a density of over 25,000 times the Sun's, which was so high that he called it "impossible".[32] As A.S. Eddington put it later, in 1927:[33]: 50 

We learn about the stars by receiving and interpreting the messages which their light brings to us. The message of the companion of Sirius when it was decoded ran: "I am composed of material 3,000 times denser than anything you have ever come across; a ton of my material would be a little nugget that you could put in a matchbox." What reply can one make to such a message? The reply which most of us made in 1914 was — "Shut up. Don't talk nonsense."

As Eddington pointed out in 1924, densities of this order implied that, according to the theory of general relativity, the light from Sirius B should be gravitationally redshifted.[22] This was confirmed when Adams measured this redshift in 1925.[34]

Material Density in kg/m3 Notes
Supermassive black hole c. 1,000[35] Critical density of a black hole of around  108 solar masses.
Water (fresh) 1,000 At STP
Osmium 22,610 Near room temperature
The core of the Sun c. 150,000
White dwarf 1 × 109[1]
Atomic nuclei 2.3 × 1017[36] Does not depend strongly on size of nucleus
Neutron star core 8.4 × 1016 – 1 × 1018
Small black hole 2 × 1030[37] Critical density of an Earth-mass black hole.

Such densities are possible because white dwarf material is not composed of atoms joined by chemical bonds, but rather consists of a plasma of unbound nuclei and electrons. There is therefore no obstacle to placing nuclei closer than normally allowed by electron orbitals limited by normal matter.[22] Eddington wondered what would happen when this plasma cooled and the energy to keep the atoms ionized was no longer sufficient.[38] This paradox was resolved by R. H. Fowler in 1926 by an application of the newly devised quantum mechanics. Since electrons obey the Pauli exclusion principle, no two electrons can occupy the same state, and they must obey Fermi–Dirac statistics, also introduced in 1926 to determine the statistical distribution of particles which satisfy the Pauli exclusion principle.[39] At zero temperature, therefore, electrons can not all occupy the lowest-energy, or ground, state; some of them would have to occupy higher-energy states, forming a band of lowest-available energy states, the Fermi sea. This state of the electrons, called degenerate, meant that a white dwarf could cool to zero temperature and still possess high energy.[38][40]

Compression of a white dwarf will increase the number of electrons in a given volume. Applying the Pauli exclusion principle, this will increase the kinetic energy of the electrons, thereby increasing the pressure.[38][41] This electron degeneracy pressure supports a white dwarf against gravitational collapse. The pressure depends only on density and not on temperature. Degenerate matter is relatively compressible; this means that the density of a high-mass white dwarf is much greater than that of a low-mass white dwarf and that the radius of a white dwarf decreases as its mass increases.[1]

The existence of a limiting mass that no white dwarf can exceed without collapsing to a neutron star is another consequence of being supported by electron degeneracy pressure. Such limiting masses were calculated for cases of an idealized, constant density star in 1929 by Wilhelm Anderson[42] and in 1930 by Edmund C. Stoner.[43] This value was corrected by considering hydrostatic equilibrium for the density profile, and the presently known value of the limit was first published in 1931 by Subrahmanyan Chandrasekhar in his paper "The Maximum Mass of Ideal White Dwarfs".[44] For a non-rotating white dwarf, it is equal to approximately 5.7M☉/μe2, where μe is the average molecular weight per electron of the star.[45]: eqn.(63)  As the carbon-12 and oxygen-16 which predominantly compose a carbon–oxygen white dwarf both have atomic numbers equal to half their atomic weight, one should take μe equal to 2 for such a star,[40] leading to the commonly quoted value of 1.4 M☉. (Near the beginning of the 20th century, there was reason to believe that stars were composed chiefly of heavy elements,[43]: 955  so, in his 1931 paper, Chandrasekhar set the average molecular weight per electron, μe, equal to 2.5, giving a limit of 0.91 M☉.) Together with William Alfred Fowler, Chandrasekhar received the Nobel Prize for this and other work in 1983.[46] The limiting mass is now called the Chandrasekhar limit.

If a white dwarf were to exceed the Chandrasekhar limit, and nuclear reactions did not take place, the pressure exerted by electrons would no longer be able to balance the force of gravity, and it would collapse into a denser object called a neutron star.[47] Carbon–oxygen white dwarfs accreting mass from a neighboring star undergo a runaway nuclear fusion reaction, which leads to a Type Ia supernova explosion in which the white dwarf may be destroyed, before it reaches the limiting mass.[48]

New research indicates that many white dwarfs – at least in certain types of galaxies – may not approach that limit by way of accretion. It has been postulated that at least some of the white dwarfs that become supernovae attain the necessary mass by colliding with one another. It may be that in elliptical galaxies such collisions are the major source of supernovae. This hypothesis is based on the fact that the X-rays produced by those galaxies are 30 to 50 times less than what is expected to be produced by type Ia supernovas of that galaxy as matter accretes on the white dwarf from its encircling companion. It has been concluded that no more than 5 percent of the supernovae in such galaxies could be created by the process of accretion onto white dwarfs. The significance of this finding is that there could be two types of supernovae, which could mean that the Chandrasekhar limit might not always apply in determining when a white dwarf goes supernova, given that two colliding white dwarfs could have a range of masses. This in turn would confuse efforts to use exploding white dwarfs as standard candles in determining distances.[49]

White dwarfs have low luminosity and therefore occupy a strip at the bottom of the Hertzsprung–Russell diagram, a graph of stellar luminosity versus color or temperature. They should not be confused with low-luminosity objects at the low-mass end of the main sequence, such as the hydrogen-fusing red dwarfs, whose cores are supported in part by thermal pressure,[50] or the even lower-temperature brown dwarfs.[51]

Mass–radius relationship

The relationship between the mass and radius of low-mass white dwarfs can be estimated using the nonrelativistic Fermi gas equation of state, which gives[40]

 

where R is the radius, M is the total mass of the star, N is the number of electrons per unit mass (dependent only on composition), me is the electron mass,   is the reduced Planck constant, and G is the gravitational constant.

Since this analysis uses the non-relativistic formula T = p2 / 2m for the kinetic energy, it is non-relativistic. When the electron velocity in a white dwarf is close to the speed of light, the kinetic energy formula approaches T = pc where c is the speed of light, and it can be shown that there is no stable equilibrium in the ultrarelativistic limit. In particular, this analysis yields the maximum mass of a white dwarf, which is[40]

 
 
Radius–mass relations for a model white dwarf. Mlimit is denoted as MCh

For a more accurate computation of the mass-radius relationship and limiting mass of a white dwarf, one must compute the equation of state which describes the relationship between density and pressure in the white dwarf material. If the density and pressure are both set equal to functions of the radius from the center of the star, the system of equations consisting of the hydrostatic equation together with the equation of state can then be solved to find the structure of the white dwarf at equilibrium. In the non-relativistic case, we will still find that the radius is inversely proportional to the cube root of the mass.[45]: eqn.(80)  Relativistic corrections will alter the result so that the radius becomes zero at a finite value of the mass. This is the limiting value of the mass – called the Chandrasekhar limit – at which the white dwarf can no longer be supported by electron degeneracy pressure. The graph on the right shows the result of such a computation. It shows how radius varies with mass for non-relativistic (blue curve) and relativistic (green curve) models of a white dwarf. Both models treat the white dwarf as a cold Fermi gas in hydrostatic equilibrium. The average molecular weight per electron, μe, has been set equal to 2. Radius is measured in standard solar radii and mass in standard solar masses.[45][52]

These computations all assume that the white dwarf is non-rotating. If the white dwarf is rotating, the equation of hydrostatic equilibrium must be modified to take into account the centrifugal pseudo-force arising from working in a rotating frame.[53] For a uniformly rotating white dwarf, the limiting mass increases only slightly. If the star is allowed to rotate nonuniformly, and viscosity is neglected, then, as was pointed out by Fred Hoyle in 1947,[54] there is no limit to the mass for which it is possible for a model white dwarf to be in static equilibrium. Not all of these model stars will be dynamically stable.[55]

Rotating white dwarfs and the estimates of their diameter in terms of the angular velocity of rotation has been treated in the rigorous mathematical literature.[56] The fine structure of the free boundary of white dwarfs has also been analysed mathematically rigorously.[57]

Radiation and cooling

The degenerate matter that makes up the bulk of a white dwarf has a very low opacity, because any absorption of a photon requires that an electron must transition to a higher empty state, which may not be possible as the energy of the photon may not be a match for the possible quantum states available to that electron, hence radiative heat transfer within a white dwarf is low; it does, however, have a high thermal conductivity. As a result, the interior of the white dwarf maintains a uniform temperature, approximately 107 K. An outer shell of non-degenerate matter cools from approximately 107 K to 104 K. This matter radiates roughly as a black body. A white dwarf remains visible for a long time, as its tenuous outer atmosphere of normal matter begins to radiate at about 107 K, upon formation, while its greater interior mass is at 107  K but cannot radiate through its normal matter shell.[58]

The visible radiation emitted by white dwarfs varies over a wide color range, from the whitish-blue color of an O, B or A-type main sequence star to the yellow-orange of a late K or early M-type star.[59] White dwarf effective surface temperatures extend from over 150,000 K[24] to barely under 4,000 K.[60][61] In accordance with the Stefan–Boltzmann law, luminosity increases with increasing surface temperature (proportional to T⁴); this surface temperature range corresponds to a luminosity from over 100 times the Sun's to under 1⁄10,000 that of the Sun's.[61] Hot white dwarfs, with surface temperatures in excess of 30,000 K, have been observed to be sources of soft (i.e., lower-energy) X-rays. This enables the composition and structure of their atmospheres to be studied by soft X-ray and extreme ultraviolet observations.[62]

White dwarfs also radiate neutrinos through the Urca process.[63] This process has more effect on hotter and younger white dwarfs.

 
A comparison between the white dwarf IK Pegasi B (center), its A-class companion IK Pegasi A (left) and the Sun (right). This white dwarf has a surface temperature of 35,500 K.

As was explained by Leon Mestel in 1952, unless the white dwarf accretes matter from a companion star or other source, its radiation comes from its stored heat, which is not replenished.[64][65]: §2.1  White dwarfs have an extremely small surface area to radiate this heat from, so they cool gradually, remaining hot for a long time.[5] As a white dwarf cools, its surface temperature decreases, the radiation which it emits reddens, and its luminosity decreases. Since the white dwarf has no energy sink other than radiation, it follows that its cooling slows with time. The rate of cooling has been estimated for a carbon white dwarf of 0.59 M☉ with a hydrogen atmosphere. After initially taking approximately 1.5 billion years to cool to a surface temperature of 7,140 K, cooling approximately 500 more kelvins to 6,590 K takes around 0.3 billion years, but the next two steps of around 500 kelvins (to 6,030 K and 5,550 K) take first 0.4 and then 1.1 billion years.[66]: Table 2 

Most observed white dwarfs have relatively high surface temperatures, between 8,000 K and 40,000 K.[25][67] A white dwarf, though, spends more of its lifetime at cooler temperatures than at hotter temperatures, so we should expect that there are more cool white dwarfs than hot white dwarfs. Once we adjust for the selection effect that hotter, more luminous white dwarfs are easier to observe, we do find that decreasing the temperature range examined results in finding more white dwarfs.[68] This trend stops when we reach extremely cool white dwarfs; few white dwarfs are observed with surface temperatures below 4,000 K,[69] and one of the coolest so far observed, WD 0346+246, has a surface temperature of approximately 3,800 K.[60][70] The reason for this is that the Universe's age is finite;[71][72] there has not been enough time for white dwarfs to cool below this temperature. The white dwarf luminosity function can therefore be used to find the time when stars started to form in a region; an estimate for the age of our Galactic disk found in this way is 8 billion years.[68] A white dwarf will eventually, in many trillions of years, cool and become a non-radiating black dwarf in approximate thermal equilibrium with its surroundings and with the cosmic background radiation. No black dwarfs are thought to exist yet.[1]

 
The white dwarf cooling sequence seen by ESA's Gaia mission

Although white dwarf material is initially plasma – a fluid composed of nuclei and electrons – it was theoretically predicted in the 1960s that at a late stage of cooling, it should crystallize, starting at its center.[73] The crystal structure is thought to be a body-centered cubic lattice.[4][74] In 1995 it was suggested that asteroseismological observations of pulsating white dwarfs yielded a potential test of the crystallization theory,[75] and in 2004, observations were made that suggested approximately 90% of the mass of BPM 37093 had crystallized.[73][76][77] Other work gives a crystallized mass fraction of between 32% and 82%.[78] As a white dwarf core undergoes crystallization into a solid phase, latent heat is released which provides a source of thermal energy that delays its cooling.[79] This effect was first confirmed in 2019 after the identification of a pile up in the cooling sequence of more than 15,000 white dwarfs observed with the Gaia satellite.[80]

Low-mass helium white dwarfs (mass < 0.20 M☉), often referred to as "extremely low-mass white dwarfs, ELM WDs" are formed in binary systems. As a result of their hydrogen-rich envelopes, residual hydrogen burning via the CNO cycle may keep these white dwarfs hot on a long timescale. In addition, they remain in a bloated proto-white dwarf stage for up to 2 Gyr before they reach the cooling track.[81]

Atmosphere and spectra

 
Artist's impression of the WD J0914+1914 system.[82]

Although most white dwarfs are thought to be composed of carbon and oxygen, spectroscopy typically shows that their emitted light comes from an atmosphere which is observed to be either hydrogen or helium dominated. The dominant element is usually at least 1,000 times more abundant than all other elements. As explained by Schatzman in the 1940s, the high surface gravity is thought to cause this purity by gravitationally separating the atmosphere so that heavy elements are below and the lighter above.[83][84]: §§5–6  This atmosphere, the only part of the white dwarf visible to us, is thought to be the top of an envelope which is a residue of the star's envelope in the AGB phase and may also contain material accreted from the interstellar medium. The envelope is believed to consist of a helium-rich layer with mass no more than 1⁄100 of the star's total mass, which, if the atmosphere is hydrogen-dominated, is overlain by a hydrogen-rich layer with mass approximately 1⁄10,000 of the stars total mass.[61][85]: §§4–5 

Although thin, these outer layers determine the thermal evolution of the white dwarf. The degenerate electrons in the bulk of a white dwarf conduct heat well. Most of a white dwarf's mass is therefore at almost the same temperature (isothermal), and it is also hot: a white dwarf with surface temperature between 8,000 K and 16,000 K will have a core temperature between approximately 5,000,000 K and 20,000,000 K. The white dwarf is kept from cooling very quickly only by its outer layers' opacity to radiation.[61]

White dwarf spectral types[24]
Primary and secondary features
A H lines present
B He I lines
C Continuous spectrum; no lines
O He II lines, accompanied by He I or H lines
Z Metal lines
Q Carbon lines present
X Unclear or unclassifiable spectrum
Secondary features only
P Magnetic white dwarf with detectable polarization
H Magnetic white dwarf without detectable polarization
E Emission lines present
V Variable

The first attempt to classify white dwarf spectra appears to have been by G. P. Kuiper in 1941,[59][86] and various classification schemes have been proposed and used since then.[87][88] The system currently in use was introduced by Edward M. Sion, Jesse L. Greenstein and their coauthors in 1983 and has been subsequently revised several times. It classifies a spectrum by a symbol which consists of an initial D, a letter describing the primary feature of the spectrum followed by an optional sequence of letters describing secondary features of the spectrum (as shown in the adjacent table), and a temperature index number, computed by dividing 50,400 K by the effective temperature. For example:

  • A white dwarf with only He I lines in its spectrum and an effective temperature of 15,000 K could be given the classification of DB3, or, if warranted by the precision of the temperature measurement, DB3.5.
  • A white dwarf with a polarized magnetic field, an effective temperature of 17,000 K, and a spectrum dominated by He I lines which also had hydrogen features could be given the classification of DBAP3.

The symbols "?" and ":" may also be used if the correct classification is uncertain.[24][59]

White dwarfs whose primary spectral classification is DA have hydrogen-dominated atmospheres. They make up the majority, approximately 80%, of all observed white dwarfs.[61] The next class in number is of DBs, approximately 16%.[89] The hot, above 15,000 K, DQ class (roughly 0.1%) have carbon-dominated atmospheres.[90] Those classified as DB, DC, DO, DZ, and cool DQ have helium-dominated atmospheres. Assuming that carbon and metals are not present, which spectral classification is seen depends on the effective temperature. Between approximately 100,000 K to 45,000 K, the spectrum will be classified DO, dominated by singly ionized helium. From 30,000 K to 12,000 K, the spectrum will be DB, showing neutral helium lines, and below about 12,000 K, the spectrum will be featureless and classified DC.[85]: §2.4 [61]

Molecular hydrogen (H2) has been detected in spectra of the atmospheres of some white dwarfs.[91]

Metal-rich white dwarfs

Around 25–33% of white dwarfs have metal lines in their spectra, which is notable because any heavy elements in a white dwarf should sink into the star's interior in just a small fraction of the star's lifetime.[92] The prevailing explanation for metal-rich white dwarfs is that they have recently accreted rocky planetesimals.[92] The bulk composition of the accreted object can be measured from the strengths of the metal lines. For example, a 2015 study of the white dwarf Ton 345 concluded that its metal abundances were consistent with those of a differentiated, rocky planet whose mantle had been eroded by the host star's wind during its asymptotic giant branch phase.[93]

Magnetic field

Magnetic fields in white dwarfs with a strength at the surface of c. 1 million gauss (100 teslas) were predicted by P. M. S. Blackett in 1947 as a consequence of a physical law he had proposed which stated that an uncharged, rotating body should generate a magnetic field proportional to its angular momentum.[94] This putative law, sometimes called the Blackett effect, was never generally accepted, and by the 1950s even Blackett felt it had been refuted.[95]: 39–43  In the 1960s, it was proposed that white dwarfs might have magnetic fields due to conservation of total surface magnetic flux that existed in its progenitor star phase.[96] A surface magnetic field of c. 100 gauss (0.01 T) in the progenitor star would thus become a surface magnetic field of c. 100·1002 = 1 million gauss (100 T) once the star's radius had shrunk by a factor of 100.[84]: §8 [97]: 484  The first magnetic white dwarf to be discovered was GJ 742 (also known as GRW +70 8247) which was identified by James Kemp, John Swedlund, John Landstreet and Roger Angel in 1970 to host a magnetic field by its emission of circularly polarized light.[98] It is thought to have a surface field of approximately 300 million gauss (30 kT).[84]: §8 

Since 1970, magnetic fields have been discovered in well over 200 white dwarfs, ranging from 2×103 to 109 gauss (0.2 T to 100 kT).[99] The large number of presently known magnetic white dwarfs is due to the fact that most white dwarfs are identified by low-resolution spectroscopy, which is able to reveal the presence of a magnetic field of 1 megagauss or more. Thus the basic identification process also sometimes results in discovery of magnetic fields.[100] It has been estimated that at least 10% of white dwarfs have fields in excess of 1 million gauss (100 T).[101][102]

The highly magnetized white dwarf in the binary system AR Scorpii was identified in 2016 as the first pulsar in which the compact object is a white dwarf instead of a neutron star.[103]

Chemical bonds

The magnetic fields in a white dwarf may allow for the existence of a new type of chemical bond, perpendicular paramagnetic bonding, in addition to ionic and covalent bonds, resulting in what has been initially described as "magnetized matter" in research published in 2012.[104]

Variability

Main article: Pulsating white dwarf
See also: Cataclysmic variables
Types of pulsating white dwarf[105][106]: §§1.1, 1.2 
DAV (GCVS: ZZA) DA spectral type, having only hydrogen absorption lines in its spectrum
DBV (GCVS: ZZB) DB spectral type, having only helium absorption lines in its spectrum
GW Vir (GCVS: ZZO) Atmosphere mostly C, He and O; may be divided into DOV and PNNV stars

Early calculations suggested that there might be white dwarfs whose luminosity varied with a period of around 10 seconds, but searches in the 1960s failed to observe this.[84]: §7.1.1 [107] The first variable white dwarf found was HL Tau 76; in 1965 and 1966, and was observed to vary with a period of approximately 12.5 minutes.[108] The reason for this period being longer than predicted is that the variability of HL Tau 76, like that of the other pulsating variable white dwarfs known, arises from non-radial gravity wave pulsations.[84]: §7  Known types of pulsating white dwarf include the DAV, or ZZ Ceti, stars, including HL Tau 76, with hydrogen-dominated atmospheres and the spectral type DA;[84]: 891, 895  DBV, or V777 Her, stars, with helium-dominated atmospheres and the spectral type DB;[61]: 3525  and GW Vir stars, sometimes subdivided into DOV and PNNV stars, with atmospheres dominated by helium, carbon, and oxygen.[106][109] GW Vir stars are not, strictly speaking, white dwarfs, but are stars which are in a position on the Hertzsprung–Russell diagram between the asymptotic giant branch and the white dwarf region. They may be called pre-white dwarfs.[106][110] These variables all exhibit small (1–30%) variations in light output, arising from a superposition of vibrational modes with periods of hundreds to thousands of seconds. Observation of these variations gives asteroseismological evidence about the interiors of white dwarfs.[111]

Formation

White dwarfs are thought to represent the end point of stellar evolution for main-sequence stars with masses from about 0.07 to 10 M☉.[4][112] The composition of the white dwarf produced will depend on the initial mass of the star. Current galactic models suggest the Milky Way galaxy currently contains about ten billion white dwarfs.[113]

Stars with very low mass

If the mass of a main-sequence star is lower than approximately half a solar mass, it will never become hot enough to fuse helium in its core. It is thought that, over a lifespan that considerably exceeds the age of the universe (c. 13.8 billion years),[9] such a star will eventually burn all its hydrogen, for a while becoming a blue dwarf, and end its evolution as a helium white dwarf composed chiefly of helium-4 nuclei.[114] Due to the very long time this process takes, it is not thought to be the origin of the observed helium white dwarfs. Rather, they are thought to be the product of mass loss in binary systems[5][7][8][115][116][117] or mass loss due to a large planetary companion.[118][119]

Stars with low to medium mass

If the mass of a main-sequence star is between 0.5 and 8 M☉ like our sun, its core will become sufficiently hot to fuse helium into carbon and oxygen via the triple-alpha process, but it will never become sufficiently hot to fuse carbon into neon. Near the end of the period in which it undergoes fusion reactions, such a star will have a carbon–oxygen core which does not undergo fusion reactions, surrounded by an inner helium-burning shell and an outer hydrogen-burning shell. On the Hertzsprung–Russell diagram, it will be found on the asymptotic giant branch. It will then expel most of its outer material, creating a planetary nebula, until only the carbon–oxygen core is left. This process is responsible for the carbon–oxygen white dwarfs which form the vast majority of observed white dwarfs.[115][120][121]

Stars with medium to high mass

If a star is massive enough, its core will eventually become sufficiently hot to fuse carbon to neon, and then to fuse neon to iron. Such a star will not become a white dwarf, because the mass of its central, non-fusing core, initially supported by electron degeneracy pressure, will eventually exceed the largest possible mass supportable by degeneracy pressure. At this point the core of the star will collapse and it will explode in a core-collapse supernova which will leave behind a remnant neutron star, black hole, or possibly a more exotic form of compact star.[112][122] Some main-sequence stars, of perhaps 8 to 10 M☉, although sufficiently massive to fuse carbon to neon and magnesium, may be insufficiently massive to fuse neon. Such a star may leave a remnant white dwarf composed chiefly of oxygen, neon, and magnesium, provided that its core does not collapse, and provided that fusion does not proceed so violently as to blow apart the star in a supernova.[123][124] Although a few white dwarfs have been identified which may be of this type, most evidence for the existence of such comes from the novae called ONeMg or neon novae. The spectra of these novae exhibit abundances of neon, magnesium, and other intermediate-mass elements which appear to be only explicable by the accretion of material onto an oxygen–neon–magnesium white dwarf.[6][125][126]

Type Iax supernova

Type Iax supernovae, that involve helium accretion by a white dwarf, have been proposed to be a channel for transformation of this type of stellar remnant. In this scenario, the carbon detonation produced in a Type Ia supernova is too weak to destroy the white dwarf, expelling just a small part of its mass as ejecta, but produces an asymmetric explosion that kicks the star, often known as a zombie star, to high speeds of a hypervelocity star. The matter processed in the failed detonation is re-accreted by the white dwarf with the heaviest elements such as iron falling to its core where it accumulates.[127] These iron-core white dwarfs would be smaller than the carbon–oxygen kind of similar mass and would cool and crystallize faster than those.[128]

Fate

Artist's concept of white dwarf aging
 
Internal structures of white dwarfs. To the left is a newly formed white dwarf, in the center is a cooling and crystallizing white dwarf, and the right is a black dwarf.

A white dwarf is stable once formed and will continue to cool almost indefinitely, eventually to become a black dwarf. Assuming that the universe continues to expand, it is thought that in 1019 to 1020 years, the galaxies will evaporate as their stars escape into intergalactic space.[129]: §IIIA  White dwarfs should generally survive galactic dispersion, although an occasional collision between white dwarfs may produce a new fusing star or a super-Chandrasekhar mass white dwarf which will explode in a Type Ia supernova.[129]: §§IIIC, IV  The subsequent lifetime of white dwarfs is thought to be on the order of the hypothetical lifetime of the proton, known to be at least 1034–1035 years. Some grand unified theories predict a proton lifetime between 1030 and 1036 years. If these theories are not valid, the proton might still decay by complicated nuclear reactions or through quantum gravitational processes involving virtual black holes; in these cases, the lifetime is estimated to be no more than 10200 years. If protons do decay, the mass of a white dwarf will decrease very slowly with time as its nuclei decay, until it loses enough mass to become a nondegenerate lump of matter, and finally disappears completely.[129]: §IV 

A white dwarf can also be cannibalized or evaporated by a companion star, causing the white dwarf to lose so much mass that it becomes a planetary mass object. The resultant object, orbiting the former companion, now host star, could be a helium planet or diamond planet.[130][131]

Debris disks and planets

 
Artist's impression of debris around a white dwarf[132]
 
Comet falling into white dwarf (artist's impression)[133]

A white dwarf's stellar and planetary system is inherited from its progenitor star and may interact with the white dwarf in various ways. There are several indications that a white dwarf has a remnant planetary system.

The most common observable evidence of a remnant planetary system is pollution of the spectrum of a white dwarf with metal absorption lines. 27–50% of white dwarfs show a spectrum polluted with metals,[134] but these heavy elements settle out in the atmosphere of white dwarfs colder than 20,000 K. The most widely accepted hypothesis is that this pollution comes from tidally disrupted rocky bodies.[135][136] The first observation of a metal-polluted white dwarf was by van Maanen[137] in 1917 at the Mount Wilson Observatory and is now recognized as the first evidence of exoplanets in astronomy.[138] The white dwarf van Maanen 2 shows iron, calcium and magnesium in its atmosphere,[139] but van Maanen misclassified it as the faintest F-type star based on the calcium H- and K-lines.[140] The following heavy elements were discovered in the atmosphere of white dwarfs: Ca, Mg, Fe, Na, Si, Cr, C, O, Al?, Sc, Ti, V, Mn, Co, Ni, Cu, Sr, S, P, N, Li, K, Be. The nitrogen in white dwarfs is thought to come from nitrogen-ice of extrasolar Kuiper Belt objects, the lithium is thought to come from accreted crust material and the beryllium is thought to come from exomoons.[138]

A less common observable evidence is infrared excess due to a flat and optically thick debris disk, which is found in around 1–4% of white dwarfs.[136] The first white dwarf with infrared excess was discovered by Zuckerman&Becklin in 1987 in the near-infrared around Giclas 29-38[141] and later confirmed as a debris disk.[142] White dwarfs hotter than 27,000 K sublimate all the dust formed by tidally disrupting a rocky body, preventing the formation of a debris disk. In colder white dwarfs, a rocky body might be tidally disrupted near the Roche radius and forced into a circular orbit by the Poynting–Robertson drag, which is stronger for less massive white dwarfs. The Poynting–Robertson drag will also cause the dust to orbit closer and closer towards the white dwarf, until it will eventually sublimate and the disk will disappear. A debris disk will have a lifetime of around a few million years for white dwarfs hotter than 10,000 K. Colder white dwarfs can have disk-lifetimes of a few 10 million years, which is enough time to tidally disrupt a second rocky body and forming a second disk around a white dwarf, such as the two rings around LSPM J0207+3331.[143]

The least common observable evidence of planetary systems are detected major or minor planets. Only a handful giant planets and a handful of minor planets are known around white dwarfs.[144] It is a growing list with discoveries of around 6 exoplanets expected with Gaia[145] and 4 exoplanets with JWST.[146]

Exoplanet orbits WD 1856+534
 
(NASA; video; 2:10)

Infrared spectroscopic observations made by NASA's Spitzer Space Telescope of the central star of the Helix Nebula suggest the presence of a dust cloud, which may be caused by cometary collisions. It is possible that infalling material from this may cause X-ray emission from the central star.[147][148] Similarly, observations made in 2004 indicated the presence of a dust cloud around the young (estimated to have formed from its AGB progenitor about 500 million years ago) white dwarf G29-38, which may have been created by tidal disruption of a comet passing close to the white dwarf.[142] Some estimations based on the metal content of the atmospheres of the white dwarfs consider that at least 15% of them may be orbited by planets or asteroids, or at least their debris.[149] Another suggested idea is that white dwarfs could be orbited by the stripped cores of rocky planets, that would have survived the red giant phase of their star but losing their outer layers and, given those planetary remnants would likely be made of metals, to attempt to detect them looking for the signatures of their interaction with the white dwarf's magnetic field.[150] Other suggested ideas of how white dwarfs are polluted with dust involve the scattering of asteroids by planets[151][152][153] or via planet-planet scattering.[154] Liberation of exomoons from their host planet could cause white dwarf pollution with dust. Either the liberation could cause asteroids to be scattered towards the white dwarf or the exomoon could be scattered into the Roche radius of the white dwarf.[155] The mechanism behind the pollution of white dwarfs in binaries was also explored as these systems are more likely to lack a major planet, but this idea cannot explain the presence of dust around single white dwarfs.[156] While old white dwarfs show evidence of dust accretion, white dwarfs older than ~1 billion years or >7000 K with dusty infrared excess were not detected[157] until the discovery of LSPM J0207+3331 in 2018, which has a cooling age of ~3 billion years. The white dwarf shows two dusty components that are being explained with two rings with different temperatures.[136]

Planets around white dwarfs
System name host star minor planet? Number of planets Mass planet (MJ) semi-major axis (au or R☉) discovery method discovery year Note Reference
PSR B1620-26 white dwarf+pulsar 1 2.5±1 23 au pulsar timing 1993 [158]
NN Serpentis PCEB: white dwarf+red dwarf 2 c: 6.91±0.54

d: 2.28±0.38

c: 5.38±0.20 au

d: 3.39±0.10 au

eclipse timing variation 2010 PCEB is surrounded by a dusty disk[159] [160]
WD 0806-661 single 1 1.5-8 2500 au direct imaging 2011 WD 0806-661 B can be interpreted as either a sub-brown dwarf or an exoplanet. [161][162]
WD J0914+1914 single 1 15-16 R☉ detection of accreted planet material viaspectroscopy 2019 likely ice giant [163]
WD 1856+534 single 1 >0.84[164] 4 R☉ transiting 2020 the white dwarf co-moves with G 229-20 A/B [165][166][167]
WD 1145+017 single minor planet 1 1.16 R☉[168] transiting 2015 [169]
SDSS J1228+1040 single minor planet 1 0.73 R☉ variable Calcium absorption line 2019 orbits within the debris disk of the white dwarf [170]
WD 0145+234 single minor planet 1 1.2 R☉[171] tidal disruption event 2019 [172]
ZTF J0139+5245 single minor planet 1 0.36 au transiting 2020 highly eccentric orbit (e>0.97)[144] [173][174]
ZTF J0328-1219 single minor planet 2 b: 2.11 R☉

c: 2.28 R☉

transiting 2021 discovery paper also describes candidates around 4 other white dwarfs [175][176]

The metal-rich white dwarf WD 1145+017 is the first white dwarf observed with a disintegrating minor planet which transits the star.[177][169] The disintegration of the planetesimal generates a debris cloud which passes in front of the star every 4.5 hours, causing a 5-minute-long fade in the star's optical brightness.[169] The depth of the transit is highly variable.[169]

The giant planet WD J0914+1914b is being evaporated by the strong ultraviolet radiation of the hot white dwarf. Part of the evaporated material is being accreted in a gaseous disk around the white dwarf. The weak hydrogen line as well as other lines in the spectrum of the white dwarf revealed the presence of the giant planet.[163]

The white dwarf WD 0145+234 shows brightening in the mid-infrared, seen in NEOWISE data. The brightening is not seen before 2018. It is interpreted as the tidal disruption of an exoasteroid, the first time such an event has been observed.[172]

WD 1856+534 is the first and only transiting major planet around a white dwarf (as of 2022).

Habitability

It has been proposed that white dwarfs with surface temperatures of less than 10,000 Kelvins could harbor a habitable zone at a distance of c. 0.005 to 0.02 AU that would last upwards of 3 billion years. This is so close that any habitable planets would be tidally locked. The goal is to search for transits of hypothetical Earth-like planets that could have migrated inward or formed there. As a white dwarf has a size similar to that of a planet, these kinds of transits would produce strong eclipses.[178] Newer research casts some doubts on this idea, given that the close orbits of those hypothetical planets around their parent stars would subject them to strong tidal forces that could render them uninhabitable by triggering a greenhouse effect.[179] Another suggested constraint to this idea is the origin of those planets. Leaving aside formation from the accretion disk surrounding the white dwarf, there are two ways a planet could end in a close orbit around stars of this kind: by surviving being engulfed by the star during its red giant phase, and then spiralling inward, or inward migration after the white dwarf has formed. The former case is implausible for low-mass bodies, as they are unlikely to survive being absorbed by their stars. In the latter case, the planets would have to expel so much orbital energy as heat, through tidal interactions with the white dwarf, that they would likely end as uninhabitable embers.[180]

Binary stars and novae

 
The merger process of two co-orbiting white dwarfs produces gravitational waves

If a white dwarf is in a binary star system and is accreting matter from its companion, a variety of phenomena may occur, including novae and Type Ia supernovae. It may also be a super-soft x-ray source if it is able to take material from its companion fast enough to sustain fusion on its surface.[181] On the other hand, phenomena in binary systems such as tidal interaction and star–disc interaction, moderated by magnetic fields or not, act on the rotation of accreting white dwarfs. In fact, the (securely known) fastest-spinning white dwarfs are members of binary systems (the fastest one being the white dwarf in CTCV J2056-3014).[182] A close binary system of two white dwarfs can radiate energy in the form of gravitational waves, causing their mutual orbit to steadily shrink until the stars merge.[183][184]

Type Ia supernovae

Main article: Type Ia supernova

The mass of an isolated, nonrotating white dwarf cannot exceed the Chandrasekhar limit of ~1.4 M☉. This limit may increase if the white dwarf is rotating rapidly and nonuniformly.[185] White dwarfs in binary systems can accrete material from a companion star, increasing both their mass and their density. As their mass approaches the Chandrasekhar limit, this could theoretically lead to either the explosive ignition of fusion in the white dwarf or its collapse into a neutron star.[47]

Accretion provides the currently favored mechanism called the single-degenerate model for Type Ia supernovae. In this model, a carbon–oxygen white dwarf accretes mass and compresses its core by pulling mass from a companion star.[48]: 14  It is believed that compressional heating of the core leads to ignition of carbon fusion as the mass approaches the Chandrasekhar limit.[48] Because the white dwarf is supported against gravity by quantum degeneracy pressure instead of by thermal pressure, adding heat to the star's interior increases its temperature but not its pressure, so the white dwarf does not expand and cool in response. Rather, the increased temperature accelerates the rate of the fusion reaction, in a runaway process that feeds on itself. The thermonuclear flame consumes much of the white dwarf in a few seconds, causing a Type Ia supernova explosion that obliterates the star.[1][48][186] In another possible mechanism for Type Ia supernovae, the double-degenerate model, two carbon–oxygen white dwarfs in a binary system merge, creating an object with mass greater than the Chandrasekhar limit in which carbon fusion is then ignited.[48]: 14 

Observations have failed to note signs of accretion leading up to Type Ia supernovae, and this is now thought to be because the star is first loaded up to above the Chandrasekhar limit while also being spun up to a very high rate by the same process. Once the accretion stops, the star gradually slows until the spin is no longer enough to prevent the explosion.[187]

The historical bright SN 1006 is thought to have been a type Ia supernova from a white dwarf, possibly the merger of two white dwarfs.[188] Tycho's Supernova of 1572 was also a type Ia supernova, and its remnant has been detected.[189] A close candidate to being a survivor of a type Ia supernova is WD 0810-353.[190]

Post-common envelope binary

Main article: Post common envelope binary

A post-common envelope binary (PCEB) is a binary consisting of a white dwarf and a closely tidally-locked red dwarf (in other cases this might be a brown dwarf instead of a red dwarf). These binaries form when the red dwarf is engulfed in the red giant phase. As the red dwarf orbits inside the common envelope, it is slowed down in the denser environment. This slowed orbital speed is compensated with a decrease of the orbital distance between the red dwarf and the core of the red giant. The red dwarf spirals inwards towards the core and might merge with the core. If this does not happen and instead the common envelope is ejected, then the binary ends up in a close orbit, consisting of a white dwarf and a red dwarf. This type of binary is called a post-common envelope binary. The evolution of the PCEB continues as the two dwarf stars orbit closer and closer due to magnetic braking and by releasing gravitational waves. The binary might evolve at some point into a cataclysmic variable, and therefore post-common envelope binaries are sometimes called pre-cataclysmic variables.

Cataclysmic variables

Main article: Cataclysmic variable star

Before accretion of material pushes a white dwarf close to the Chandrasekhar limit, accreted hydrogen-rich material on the surface may ignite in a less destructive type of thermonuclear explosion powered by hydrogen fusion. These surface explosions can be repeated as long as the white dwarf's core remains intact. This weaker kind of repetitive cataclysmic phenomenon is called a (classical) nova. Astronomers have also observed dwarf novae, which have smaller, more frequent luminosity peaks than the classical novae. These are thought to be caused by the release of gravitational potential energy when part of the accretion disc collapses onto the star, rather than through a release of energy due to fusion. In general, binary systems with a white dwarf accreting matter from a stellar companion are called cataclysmic variables. As well as novae and dwarf novae, several other classes of these variables are known, including polars and intermediate polars, both of which feature highly magnetic white dwarfs.[1][48][191][192] Both fusion- and accretion-powered cataclysmic variables have been observed to be X-ray sources.[192]

Other non-pre-supernova binaries

Other non-pro-supernova binaries include binaries that consist of a main sequence star (or giant) and a white dwarf. The binary Sirius AB is probably the most famous example. White dwarfs can also exist as binaries or multiple star systems that only consist of white dwarfs. An example of a resolved triple white dwarf system is WD J1953-1019, discovered with Gaia DR2 data. One interesting field is the study of remnant planetary systems around white dwarfs. While stars are bright and often outshine the exoplanets and brown dwarfs that orbit them, the white dwarfs are faint. This allows astronomers to study these brown dwarfs or exoplanets in more detail. The sub-brown dwarf around the white dwarf WD 0806−661 is one such example.

Nearest

White Dwarfs within 25 Light Years[193]
Identifier WD Number Distance (ly) Type Absolute
magnitude 		Mass
(M☉) 		Luminosity
(L☉) 		Age (Gyr) Objects in system
Sirius B 0642–166 8.66 DA 11.18 0.98 0.0295 0.10 2
Procyon B 0736+053 11.46 DQZ 13.20 0.63 0.00049 1.37 2
Van Maanen 2 0046+051 14.07 DZ 14.09 0.68 0.00017 3.30 1
LP 145-141 1142–645 15.12 DQ 12.77 0.61 0.00054 1.29 1
40 Eridani B 0413-077 16.39 DA 11.27 0.59 0.0141 0.12 3
Stein 2051 B 0426+588 17.99 DC 13.43 0.69 0.00030 2.02 2
G 240-72 1748+708 20.26 DQ 15.23 0.81 0.000085 5.69 1
Gliese 223.2 0552–041 21.01 DZ 15.29 0.82 0.000062 7.89 1
Gliese 3991 B[194] 1708+437 24.23 D?? >15 0.5 <0.000086 >6 2

Gallery

  •  
    Illustration of rocky debris around a white dwarf
    [195]
  •  

    Cocoon of a new white dwarf in the centre of NGC 2440

  •  
    Artist's impression of an evolving white dwarf and millisecond pulsar binary system
    [196]
  •  
    Illustration of an ultracool dwarf with a companion white dwarf
    [197]

See also

References

  1. ^ a b c d e f g h i Johnson, J. (2007). "Extreme stars: White dwarfs & neutron stars" (Lecture notes). Astronomy 162. Ohio State University. from the original on 31 March 2012. Retrieved 17 October 2011.
  2. ^ Henry, T.J. (1 January 2009). "The one hundred nearest star systems". Research Consortium on Nearby Stars. from the original on 12 November 2007. Retrieved 21 July 2010.
  3. ^ a b c d Evry L. Schatzman (1958). White Dwarfs. North-Holland Publishing Company. ISBN 978-0-598-58212-6.
  4. ^ a b c d Fontaine, G.; Brassard, P.; Bergeron, P. (2001). "The potential of white dwarf cosmochronology". Publications of the Astronomical Society of the Pacific. 113 (782): 409–435. Bibcode:2001PASP..113..409F. doi:10.1086/319535.
  5. ^ a b c d e Richmond, M. "Late stages of evolution for low-mass stars". Lecture notes, Physics 230. Rochester Institute of Technology. from the original on 4 September 2017. Retrieved 3 May 2007.
  6. ^ a b Werner, K.; Hammer, N.J.; Nagel, T.; Rauch, T.; Dreizler, S. (2005). On possible oxygen / neon white dwarfs: H1504+65 and the white dwarf donors in ultracompact X-ray binaries. 14th European Workshop on White Dwarfs. Vol. 334. p. 165. arXiv:astro-ph/0410690. Bibcode:2005ASPC..334..165W.
  7. ^ a b Liebert, James; Bergeron, P.; Eisenstein, D.; Harris, H. C.; Kleinman, S. J.; Nitta, A.; Krzesinski, J. (2004). "A helium white dwarf of extremely low mass". The Astrophysical Journal. 606 (2): L147. arXiv:astro-ph/0404291. Bibcode:2004ApJ...606L.147L. doi:10.1086/421462. S2CID 118894713.
  8. ^ a b "Cosmic weight loss: The lowest mass white dwarf" (Press release). Harvard-Smithsonian Center for Astrophysics. 17 April 2007. from the original on 22 April 2007. Retrieved 20 April 2007.
  9. ^ a b Spergel, D.N.; Bean, R.; Doré, O.; Nolta, M.R.; Bennett, C.L.; Dunkley, J.; et al. (2007). "Wilkinson Microwave Anisotropy Probe (WMAP) three year results: Implications for cosmology". The Astrophysical Journal Supplement Series. 170 (2): 377–408. arXiv:astro-ph/0603449. Bibcode:2007ApJS..170..377S. doi:10.1086/513700. S2CID 1386346.
  10. ^ §3, Heger, A.; Fryer, C.L.; Woosley, S.E.; Langer, N.; Hartmann, D.H. (2003). "How massive single stars end their life". Astrophysical Journal. 591 (1): 288–300. arXiv:astro-ph/0212469. Bibcode:2003ApJ...591..288H. doi:10.1086/375341. S2CID 59065632.
  11. ^ Herschel, W. (1785). "Catalogue of Double Stars". Philosophical Transactions of the Royal Society of London. 75: 40–126. Bibcode:1785RSPT...75...40H. doi:10.1098/rstl.1785.0006. JSTOR 106749. S2CID 186209747.
  12. ^ a b c Holberg, J. B. (2005). How degenerate stars came to be known as 'white dwarfs'. American Astronomical Society meeting 207. Vol. 207. p. 1503. Bibcode:2005AAS...20720501H.
  13. ^ Adams, W.S. (1914). "An A-type star of very low luminosity". Publications of the Astronomical Society of the Pacific. 26 (155): 198. Bibcode:1914PASP...26..198A. doi:10.1086/122337.
  14. ^ a b Bessel, F.W. (1844). "On the variations of the proper motions of Procyon and Sirius". Monthly Notices of the Royal Astronomical Society. 6 (11): 136–141. Bibcode:1844MNRAS...6R.136B. doi:10.1093/mnras/6.11.136a.
  15. ^ a b Flammarion, Camille (1877). "The companion of Sirius". Astronomical Register. 15: 186. Bibcode:1877AReg...15..186F.
  16. ^ Adams, W.S. (1915). "The spectrum of the companion of Sirius". Publications of the Astronomical Society of the Pacific. 27 (161): 236. Bibcode:1915PASP...27..236A. doi:10.1086/122440.
  17. ^ van Maanen, A. (1917). "Two faint stars with large proper motion". Publications of the Astronomical Society of the Pacific. 29 (172): 258. Bibcode:1917PASP...29..258V. doi:10.1086/122654.
  18. ^ Luyten, W.J. (1922). "The mean parallax of early-type stars of determined proper motion and apparent magnitude". Publications of the Astronomical Society of the Pacific. 34 (199): 156. Bibcode:1922PASP...34..156L. doi:10.1086/123176.
  19. ^ Luyten, W.J. (1922). "Note on some faint early-type stars with large proper motions". Publications of the Astronomical Society of the Pacific. 34 (197): 54. Bibcode:1922PASP...34...54L. doi:10.1086/123146.
  20. ^ Luyten, W.J. (1922). "Additional note on faint early-type stars with large proper motions". Publications of the Astronomical Society of the Pacific. 34 (198): 132. Bibcode:1922PASP...34..132L. doi:10.1086/123168.
  21. ^ Aitken, R.G. (1922). "Comet c 1922 (Baade)". Publications of the Astronomical Society of the Pacific. 34 (202): 353. Bibcode:1922PASP...34..353A. doi:10.1086/123244.
  22. ^ a b c Eddington, A. S. (1924). "On the relation between the masses and luminosities of the stars". Monthly Notices of the Royal Astronomical Society. 84 (5): 308–333. Bibcode:1924MNRAS..84..308E. doi:10.1093/mnras/84.5.308.
  23. ^ Luyten, W.J. (1950). "The search for white dwarfs". The Astronomical Journal. 55: 86. Bibcode:1950AJ.....55...86L. doi:10.1086/106358.
  24. ^ a b c d McCook, George P.; Sion, Edward M. (1999). "A catalog of spectroscopically identified white dwarfs". The Astrophysical Journal Supplement Series. 121 (1): 1–130. Bibcode:1999ApJS..121....1M. doi:10.1086/313186.
  25. ^ a b Eisenstein, Daniel J.; Liebert, James; Harris, Hugh C.; Kleinman, S. J.; Nitta, Atsuko; Silvestri, Nicole; et al. (2006). "A catalog of spectroscopically confirmed white dwarfs from the Sloan Digital Sky Survey, data release 4". The Astrophysical Journal Supplement Series. 167 (1): 40–58. arXiv:astro-ph/0606700. Bibcode:2006ApJS..167...40E. doi:10.1086/507110. S2CID 13829139.
  26. ^ Kilic, M.; Allende Prieto, C.; Brown, Warren R.; Koester, D. (2007). "The lowest mass white dwarf". The Astrophysical Journal. 660 (2): 1451–1461. arXiv:astro-ph/0611498. Bibcode:2007ApJ...660.1451K. doi:10.1086/514327. S2CID 18587748.
  27. ^ a b Kepler, S.O.; Kleinman, S.J.; Nitta, A.; Koester, D.; Castanheira, B.G.; Giovannini, O.; Costa, A.F.M.; Althaus, L. (2007). "White dwarf mass distribution in the SDSS". Monthly Notices of the Royal Astronomical Society. 375 (4): 1315–1324. arXiv:astro-ph/0612277. Bibcode:2007MNRAS.375.1315K. doi:10.1111/j.1365-2966.2006.11388.x. S2CID 10892288.
  28. ^ Shipman, H.L. (1979). "Masses and radii of white-dwarf stars. III – Results for 110 hydrogen-rich and 28 helium-rich stars". The Astrophysical Journal. 228: 240. Bibcode:1979ApJ...228..240S. doi:10.1086/156841.
  29. ^ Sandin, F. (2005). Exotic Phases of Matter in Compact Stars (PDF) (Licentiate thesis). Luleå University of Technology. (PDF) from the original on 15 August 2011. Retrieved 20 August 2011.
  30. ^ Boss, L. (1910). Preliminary General Catalogue of 6188 stars for the epoch 1900. Carnegie Institution of Washington. Bibcode:1910pgcs.book.....B. LCCN 10009645 – via Archive.org.
  31. ^ Liebert, James; Young, P. A.; Arnett, D.; Holberg, J. B.; Williams, K. A. (2005). "The age and progenitor mass of Sirius B". The Astrophysical Journal. 630 (1): L69. arXiv:astro-ph/0507523. Bibcode:2005ApJ...630L..69L. doi:10.1086/462419. S2CID 8792889.
  32. ^ Öpik, E. (1916). "The densities of visual binary stars". The Astrophysical Journal. 44: 292. Bibcode:1916ApJ....44..292O. doi:10.1086/142296.
  33. ^ Eddington, A.S. (1927). Stars and Atoms. Clarendon Press. LCCN 27015694.
  34. ^ Adams, W. S. (1925). "The Relativity Displacement of the Spectral Lines in the Companion of Sirius". Proceedings of the National Academy of Sciences. 11 (7): 382–387. Bibcode:1925PNAS...11..382A. doi:10.1073/pnas.11.7.382. PMC 1086032. PMID 16587023.
  35. ^ Celotti, A.; Miller, J.C.; Sciama, D.W. (1999). "Astrophysical evidence for the existence of black holes". Class. Quantum Grav. 16 (12A): A3–A21. arXiv:astro-ph/9912186. Bibcode:1999CQGra..16A...3C. doi:10.1088/0264-9381/16/12A/301. S2CID 17677758.
  36. ^ Nave, C. R. "Nuclear Size and Density". HyperPhysics. Georgia State University. from the original on 6 July 2009. Retrieved 26 June 2009.
  37. ^ Adams, Steve (1997). Relativity: an introduction to space-time physics. Relativity: An Introduction to Space-Time Physics. London; Bristol: CRC Press. p. 240. Bibcode:1997rist.book.....A. ISBN 978-0-7484-0621-0.
  38. ^ a b c Fowler, R. H. (1926). "On dense matter". Monthly Notices of the Royal Astronomical Society. 87 (2): 114–122. Bibcode:1926MNRAS..87..114F. doi:10.1093/mnras/87.2.114.
  39. ^ Hoddeson, L. H.; Baym, G. (1980). "The Development of the Quantum Mechanical Electron Theory of Metals: 1900–28". Proceedings of the Royal Society of London. 371 (1744): 8–23. Bibcode:1980RSPSA.371....8H. doi:10.1098/rspa.1980.0051. JSTOR 2990270. S2CID 120476662.
  40. ^ a b c d "Estimating Stellar Parameters from Energy Equipartition". ScienceBits. from the original on 22 May 2012. Retrieved 9 May 2007.
  41. ^ Bean, R. (PDF). Lecture notes, Astronomy 211. Cornell University. Archived from the original (PDF) on 25 September 2007. Retrieved 21 September 2007.
  42. ^ Anderson, W. (1929). "Über die Grenzdichte der Materie und der Energie". Zeitschrift für Physik (in German). 56 (11–12): 851–856. Bibcode:1929ZPhy...56..851A. doi:10.1007/BF01340146. S2CID 122576829.
  43. ^ a b Stoner, C. (1930). "The Equilibrium of Dense Stars". Philosophical Magazine. 9: 944.
  44. ^ Chandrasekhar, S. (1931). "The Maximum Mass of Ideal White Dwarfs". The Astrophysical Journal. 74: 81. Bibcode:1931ApJ....74...81C. doi:10.1086/143324.
  45. ^ a b c Chandrasekhar, S. (1935). "The highly collapsed configurations of a stellar mass (Second paper)". Monthly Notices of the Royal Astronomical Society. 95 (3): 207–225. Bibcode:1935MNRAS..95..207C. doi:10.1093/mnras/95.3.207.
  46. ^ "The Nobel Prize in Physics 1983". The Nobel Foundation. from the original on 6 May 2007. Retrieved 4 May 2007.
  47. ^ a b Canal, R.; Gutierrez, J. (1997). "The Possible White Dwarf-Neutron Star Connection". White Dwarfs. Astrophysics and Space Science Library. Vol. 214. pp. 49–55. arXiv:astro-ph/9701225. Bibcode:1997ASSL..214...49C. doi:10.1007/978-94-011-5542-7_7. ISBN 978-94-010-6334-0. S2CID 9288287.
  48. ^ a b c d e f Hillebrandt, W.; Niemeyer, J. C. (2000). "Type IA supernova explosion models". Annual Review of Astronomy and Astrophysics. 38: 191–230. arXiv:astro-ph/0006305. Bibcode:2000ARA&A..38..191H. doi:10.1146/annurev.astro.38.1.191. S2CID 10210550.
  49. ^ Overbye, D. (22 February 2010). "From the Clash of White Dwarfs, the Birth of a Supernova". The New York Times. from the original on 25 February 2010. Retrieved 22 February 2010.
  50. ^ Chabrier, G.; Baraffe, I. (2000). "Theory of low-Mass stars and substellar objects". Annual Review of Astronomy and Astrophysics. 38: 337–377. arXiv:astro-ph/0006383. Bibcode:2000ARA&A..38..337C. doi:10.1146/annurev.astro.38.1.337. S2CID 59325115.
  51. ^ Kaler, J. "The Hertzsprung-Russell (HR) diagram". from the original on 31 August 2009. Retrieved 5 May 2007.
  52. ^ "Basic symbols". Standards for Astronomical Catalogues, Version 2.0. VizieR. from the original on 8 May 2017. Retrieved 12 January 2007.
  53. ^ Tohline, J. E. "The Structure, Stability, and Dynamics of Self-Gravitating Systems". from the original on 27 June 2010. Retrieved 30 May 2007.
  54. ^ Hoyle, F. (1947). "Stars, Distribution and Motions of, Note on equilibrium configurations for rotating white dwarfs". Monthly Notices of the Royal Astronomical Society. 107 (2): 231–236. Bibcode:1947MNRAS.107..231H. doi:10.1093/mnras/107.2.231.
  55. ^ Ostriker, J. P.; Bodenheimer, P. (1968). "Rapidly Rotating Stars. II. Massive White Dwarfs". The Astrophysical Journal. 151: 1089. Bibcode:1968ApJ...151.1089O. doi:10.1086/149507.
  56. ^ Chanillo, Sagun; Li, Yan Yan (1994). "On diameters of uniformly rotating stars". Communications in Mathematical Physics. 166 (2): 417. Bibcode:1994CMaPh.166..417C. doi:10.1007/BF02112323. S2CID 8372549.
  57. ^ Chanillo, Sagun; Weiss, Georg S. (2012). "A remark on the geometry of uniformly rotating stars". Journal of Differential Equations. 253 (2): 553. arXiv:1109.3046. Bibcode:2012JDE...253..553C. doi:10.1016/j.jde.2012.04.011. S2CID 144301.
  58. ^ Kutner, M. L. (2003). Astronomy: A physical perspective. Cambridge University Press. p. 189. ISBN 978-0-521-52927-3. Retrieved 28 February 2016.
  59. ^ a b c Sion, E. M.; Greenstein, J. L.; Landstreet, J. D.; Liebert, James; Shipman, H. L.; Wegner, G. A. (1983). "A proposed new white dwarf spectral classification system". The Astrophysical Journal. 269: 253. Bibcode:1983ApJ...269..253S. doi:10.1086/161036.
  60. ^ a b Hambly, N. C.; Smartt, S. J.; Hodgkin, S. T. (1997). "WD 0346+246: A Very Low Luminosity, Cool Degenerate in Taurus". The Astrophysical Journal. 489 (2): L157. Bibcode:1997ApJ...489L.157H. doi:10.1086/316797.
  61. ^ a b c d e f g Fontaine, G.; Wesemael, F. (2001). "White dwarfs". In Murdin, P. (ed.). Encyclopedia of Astronomy and Astrophysics. IOP Publishing/Nature Publishing Group. ISBN 978-0-333-75088-9.
  62. ^ Heise, J. (1985). "X-ray emission from isolated hot white dwarfs". Space Science Reviews. 40 (1–2): 79–90. Bibcode:1985SSRv...40...79H. doi:10.1007/BF00212870. S2CID 120431159.
  63. ^ Lesaffre, P.; Podsiadlowski, Ph.; Tout, C. A. (2005). "A two-stream formalism for the convective Urca process". Monthly Notices of the Royal Astronomical Society. 356 (1): 131–144. arXiv:astro-ph/0411016. Bibcode:2005MNRAS.356..131L. doi:10.1111/j.1365-2966.2004.08428.x. S2CID 15797437.
  64. ^ Mestel, L. (1952). "On the theory of white dwarf stars. I. The energy sources of white dwarfs". Monthly Notices of the Royal Astronomical Society. 112 (6): 583–597. Bibcode:1952MNRAS.112..583M. doi:10.1093/mnras/112.6.583.
  65. ^ Kawaler, S. D. (1998). White Dwarf Stars and the Hubble Deep Field. The Hubble Deep Field: Proceedings of the Space Telescope Science Institute Symposium. p. 252. arXiv:astro-ph/9802217. Bibcode:1998hdf..symp..252K. ISBN 978-0-521-63097-9.
  66. ^ Bergeron, P.; Ruiz, M. T.; Leggett, S. K. (1997). "The Chemical Evolution of Cool White Dwarfs and the Age of the Local Galactic Disk". The Astrophysical Journal Supplement Series. 108 (1): 339–387. Bibcode:1997ApJS..108..339B. doi:10.1086/312955.
  67. ^ McCook, G. P.; Sion, E. M. (1999). "A Catalogue of Spectroscopically Identified White Dwarfs". The Astrophysical Journal Supplement Series. 121 (1): 1–130. Bibcode:1999ApJS..121....1M. doi:10.1086/313186.
  68. ^ a b Leggett, S. K.; Ruiz, M. T.; Bergeron, P. (1998). "The Cool White Dwarf Luminosity Function and the Age of the Galactic Disk". The Astrophysical Journal. 497 (1): 294–302. Bibcode:1998ApJ...497..294L. doi:10.1086/305463.
  69. ^ Gates, E.; Gyuk, G.; Harris, H. C.; Subbarao, M.; Anderson, S.; Kleinman, S. J.; Liebert, James; Brewington, H.; et al. (2004). "Discovery of New Ultracool White Dwarfs in the Sloan Digital Sky Survey". The Astrophysical Journal. 612 (2): L129. arXiv:astro-ph/0405566. Bibcode:2004ApJ...612L.129G. doi:10.1086/424568. S2CID 7570539.
  70. ^ Kilic, M.; Thorstensen, J. R.; Kowalski, P. M.; Andrews, J. (2012). "11–12 Gyr old white dwarfs 30 pc away". Monthly Notices of the Royal Astronomical Society: Letters. 423 (1): L132–L136. arXiv:1204.2570. Bibcode:2012MNRAS.423L.132K. doi:10.1111/j.1745-3933.2012.01271.x.
  71. ^ Winget, D. E.; Hansen, C. J.; Liebert, James; Van Horn, H. M.; Fontaine, G.; Nather, R. E.; Kepler, S. O.; Lamb, D. Q. (1987). "An independent method for determining the age of the universe". The Astrophysical Journal. 315: L77. Bibcode:1987ApJ...315L..77W. doi:10.1086/184864. hdl:10183/108730.
  72. ^ Trefil, J. S. (2004). The Moment of Creation: Big Bang Physics from Before the First Millisecond to the Present Universe. Dover Publications. ISBN 978-0-486-43813-9.
  73. ^ a b Metcalfe, T. S.; Montgomery, M. H.; Kanaan, A. (2004). "Testing White Dwarf Crystallization Theory with Asteroseismology of the Massive Pulsating DA Star BPM 37093". The Astrophysical Journal. 605 (2): L133. arXiv:astro-ph/0402046. Bibcode:2004ApJ...605L.133M. doi:10.1086/420884. S2CID 119378552.
  74. ^ Barrat, J. L.; Hansen, J. P.; Mochkovitch, R. (1988). "Crystallization of carbon-oxygen mixtures in white dwarfs". Astronomy and Astrophysics. 199 (1–2): L15. Bibcode:1988A&A...199L..15B.
  75. ^ Winget, D. E. (1995). "The Status of White Dwarf Asteroseismology and a Glimpse of the Road Ahead". Baltic Astronomy. 4 (2): 129. Bibcode:1995BaltA...4..129W. doi:10.1515/astro-1995-0209.
  76. ^ Whitehouse, David (16 February 2004). . BBC News. Archived from the original on 5 February 2007. Retrieved 6 January 2007.
  77. ^ Kanaan, A.; Nitta, A.; Winget, D. E.; Kepler, S. O.; Montgomery, M. H.; Metcalfe, T. S.; Oliveira, H.; Fraga, L.; et al. (2005). "Whole Earth Telescope observations of BPM 37093: A seismological test of crystallization theory in white dwarfs". Astronomy and Astrophysics. 432 (1): 219–224. arXiv:astro-ph/0411199. Bibcode:2005A&A...432..219K. doi:10.1051/0004-6361:20041125. S2CID 7297628.
  78. ^ Brassard, P.; Fontaine, G. (2005). "Asteroseismology of the Crystallized ZZ Ceti Star BPM 37093: A Different View". The Astrophysical Journal. 622 (1): 572–576. Bibcode:2005ApJ...622..572B. doi:10.1086/428116.
  79. ^ Hansen, B.M.S.; Liebert, James (2003). "Cool White Dwarfs". Annual Review of Astronomy and Astrophysics. 41: 465. Bibcode:2003ARA&A..41..465H. doi:10.1146/annurev.astro.41.081401.155117.
  80. ^ Tremblay, P.-E.; Fontaine, G.; Fusillo, N. P. G.; Dunlap, B. H.; Gänsicke, B. T.; Hollands, M. H.; Hermes, J. J.; Marsh, T. R.; Cukanovaite, E.; Cunningham, T. (2019). "Core crystallization and pile-up in the cooling sequence of evolving white dwarfs" (PDF). Nature. 565 (7738): 202–205. arXiv:1908.00370. Bibcode:2019Natur.565..202T. doi:10.1038/s41586-018-0791-x. PMID 30626942. S2CID 58004893. (PDF) from the original on 23 July 2019. Retrieved 23 July 2019.
  81. ^ Istrate; et al. (2014). "The timescale of low-mass proto-helium white dwarf evolution". Astronomy and Astrophysics. 571: L3. arXiv:1410.5471. Bibcode:2014A&A...571L...3I. doi:10.1051/0004-6361/201424681. S2CID 55152203.
  82. ^ "First Giant Planet around White Dwarf Found – ESO observations indicate the Neptune-like exoplanet is evaporating". www.eso.org. from the original on 4 December 2019. Retrieved 4 December 2019.
  83. ^ Schatzman, E. (1945). "Théorie du débit d'énergie des naines blanches". Annales d'Astrophysique. 8: 143. Bibcode:1945AnAp....8..143S.
  84. ^ a b c d e f Koester, D.; Chanmugam, G. (1990). "Physics of white dwarf stars". Reports on Progress in Physics. 53 (7): 837–915. Bibcode:1990RPPh...53..837K. doi:10.1088/0034-4885/53/7/001. S2CID 122582479.
  85. ^ a b Kawaler, S. D. (1997). "White Dwarf Stars". In Kawaler, S. D.; Novikov, I.; Srinivasan, G. (eds.). Stellar remnants. 1997. ISBN 978-3-540-61520-0.
  86. ^ Kuiper, G. P. (1941). "List of Known White Dwarfs". Publications of the Astronomical Society of the Pacific. 53 (314): 248. Bibcode:1941PASP...53..248K. doi:10.1086/125335.
  87. ^ Luyten, W. J. (1952). "The Spectra and Luminosities of White Dwarfs". The Astrophysical Journal. 116: 283. Bibcode:1952ApJ...116..283L. doi:10.1086/145612.
  88. ^ Greenstein, J. L. (1960). Stellar atmospheres. University of Chicago Press. Bibcode:1960stat.book.....G. LCCN 61-9138.
  89. ^ Kepler, S. O.; Kleinman, S. J.; Nitta, A.; Koester, D.; Castanheira, B. G.; Giovannini, O.; Costa, A. F. M.; Althaus, L. (2007). "White dwarf mass distribution in the SDSS". Monthly Notices of the Royal Astronomical Society. 375 (4): 1315–1324. arXiv:astro-ph/0612277. Bibcode:2007MNRAS.375.1315K. doi:10.1111/j.1365-2966.2006.11388.x. S2CID 10892288.
  90. ^ Dufour, P.; Liebert, James; Fontaine, G.; Behara, N. (2007). "White dwarf stars with carbon atmospheres". Nature. 450 (7169): 522–4. arXiv:0711.3227. Bibcode:2007Natur.450..522D. doi:10.1038/nature06318. PMID 18033290. S2CID 4398697.
  91. ^ Xu, S.; Jura, M.; Koester, D.; Klein, B.; Zuckerman, B. (2013). "Discovery of Molecular Hydrogen in White Dwarf Atmospheres". The Astrophysical Journal. 766 (2): L18. arXiv:1302.6619. Bibcode:2013ApJ...766L..18X. doi:10.1088/2041-8205/766/2/L18. S2CID 119248244.
  92. ^ a b Jura, M.; Young, E.D. (1 January 2014). "Extrasolar Cosmochemistry". Annual Review of Earth and Planetary Sciences. 42 (1): 45–67. Bibcode:2014AREPS..42...45J. doi:10.1146/annurev-earth-060313-054740.
  93. ^ Wilson, D.J.; Gänsicke, B.T.; Koester, D.; Toloza, O.; Pala, A. F.; Breedt, E.; Parsons, S.G. (11 August 2015). "The composition of a disrupted extrasolar planetesimal at SDSS J0845+2257 (Ton 345)". Monthly Notices of the Royal Astronomical Society. 451 (3): 3237–3248. arXiv:1505.07466. Bibcode:2015MNRAS.451.3237W. doi:10.1093/mnras/stv1201. S2CID 54049842.
  94. ^ Blackett, P. M. S. (1947). "The Magnetic Field of Massive Rotating Bodies". Nature. 159 (4046): 658–66. Bibcode:1947Natur.159..658B. doi:10.1038/159658a0. PMID 20239729. S2CID 4133416.
  95. ^ Lovell, B. (1975). "Patrick Maynard Stuart Blackett, Baron Blackett, of Chelsea. 18 November 1897 – 13 July 1974". Biographical Memoirs of Fellows of the Royal Society. 21: 1–115. doi:10.1098/rsbm.1975.0001. JSTOR 769678. S2CID 74674634.
  96. ^ Landstreet, John D. (1967). "Synchrotron radiation of neutrinos and its astrophysical significance". Physical Review. 153 (5): 1372–1377. Bibcode:1967PhRv..153.1372L. doi:10.1103/PhysRev.153.1372.
  97. ^ Ginzburg, V. L.; Zheleznyakov, V. V.; Zaitsev, V. V. (1969). "Coherent mechanisms of radio emission and magnetic models of pulsars". Astrophysics and Space Science. 4 (4): 464–504. Bibcode:1969Ap&SS...4..464G. doi:10.1007/BF00651351. S2CID 119003761.
  98. ^ Kemp, J.C.; Swedlund, J.B.; Landstreet, J.D.; Angel, J.R.P. (1970). "Discovery of circularly polarized light from a white dwarf". The Astrophysical Journal. 161: L77. Bibcode:1970ApJ...161L..77K. doi:10.1086/180574.
  99. ^ Ferrario, Lilia; de Martino, Domtilla; Gaensicke, Boris (2015). "Magnetic white dwarfs". Space Science Reviews. 191 (1–4): 111–169. arXiv:1504.08072. Bibcode:2015SSRv..191..111F. doi:10.1007/s11214-015-0152-0. S2CID 119057870.
  100. ^ Kepler, S.O.; Pelisoli, I.; Jordan, S.; Kleinman, S.J.; Koester, D.; Kuelebi, B.; Pecanha, V.; Castanhiera, B.G.; Nitta, A.; Costa, J.E.S.; Winget, D.E.; Kanaan, A.; Fraga, L. (2013). "Magnetic white dwarf stars in the Sloan Digital Sky Survey". Monthly Notices of the Royal Astronomical Society. 429 (4): 2934–2944. arXiv:1211.5709. Bibcode:2013MNRAS.429.2934K. doi:10.1093/mnras/sts522. S2CID 53316287.
  101. ^ Landstreet, J.D.; Bagnulo, S.; Valyavin, G.G.; Fossati, L.; Jordan, S.; Monin, D.; Wade, G.A. (2012). "On the incidence of weak magnetic fields in DA white dwarfs". Astronomy and Astrophysics. 545 (A30): 9pp. arXiv:1208.3650. Bibcode:2012A&A...545A..30L. doi:10.1051/0004-6361/201219829. S2CID 55153825.
  102. ^ Liebert, James; Bergeron, P.; Holberg, J. B. (2003). "The True Incidence of Magnetism Among Field White Dwarfs". The Astronomical Journal. 125 (1): 348–353. arXiv:astro-ph/0210319. Bibcode:2003AJ....125..348L. doi:10.1086/345573. S2CID 9005227.
  103. ^ Buckley, D.A.H.; Meintjes, P.J.; Potter, S.B.; Marsh, T.R.; Gänsicke, B.T. (23 January 2017). "Polarimetric evidence of a white dwarf pulsar in the binary system AR Scorpii". Nature Astronomy. 1 (2): 0029. arXiv:1612.03185. Bibcode:2017NatAs...1E..29B. doi:10.1038/s41550-016-0029. S2CID 15683792.
  104. ^ Merali, Zeeya (19 July 2012). "Stars draw atoms closer together". Nature News & Comment. Nature. doi:10.1038/nature.2012.11045. from the original on 20 July 2012. Retrieved 21 July 2012.
  105. ^ . Centre deDonnées astronomiques de Strasbourg. Association Française des Observateurs d'Etoiles Variables. Archived from the original on 5 February 2007. Retrieved 6 June 2007.
  106. ^ a b c Quirion, P.-O.; Fontaine, G.; Brassard, P. (2007). "Mapping the Instability Domains of GW Vir Stars in the Effective Temperature–Surface Gravity Diagram". The Astrophysical Journal Supplement Series. 171 (1): 219–248. Bibcode:2007ApJS..171..219Q. doi:10.1086/513870.
  107. ^ Lawrence, G. M.; Ostriker, J. P.; Hesser, J. E. (1967). "Ultrashort-Period Stellar Oscillations. I. Results from White Dwarfs, Old Novae, Central Stars of Planetary Nebulae, 3c 273, and Scorpius XR-1". The Astrophysical Journal. 148: L161. Bibcode:1967ApJ...148L.161L. doi:10.1086/180037.
  108. ^ Landolt, A. U. (1968). "A New Short-Period Blue Variable". The Astrophysical Journal. 153: 151. Bibcode:1968ApJ...153..151L. doi:10.1086/149645.
  109. ^ Nagel, T.; Werner, K. (2004). "Detection of non-radial g-mode pulsations in the newly discovered PG 1159 star HE 1429-1209". Astronomy and Astrophysics. 426 (2): L45. arXiv:astro-ph/0409243. Bibcode:2004A&A...426L..45N. doi:10.1051/0004-6361:200400079. S2CID 9481357.
  110. ^ O'Brien, M. S. (2000). "The Extent and Cause of the Pre–White Dwarf Instability Strip". The Astrophysical Journal. 532 (2): 1078–1088. arXiv:astro-ph/9910495. Bibcode:2000ApJ...532.1078O. doi:10.1086/308613. S2CID 115958740.
  111. ^ Winget, D. E. (1998). "Asteroseismology of white dwarf stars". Journal of Physics: Condensed Matter. 10 (49): 11247–11261. Bibcode:1998JPCM...1011247W. doi:10.1088/0953-8984/10/49/014. S2CID 250749380.
  112. ^ a b Heger, A.; Fryer, C. L.; Woosley, S. E.; Langer, N.; Hartmann, D. H. (2003). "How Massive Single Stars End Their Life". The Astrophysical Journal. 591 (1): 288–300. arXiv:astro-ph/0212469. Bibcode:2003ApJ...591..288H. doi:10.1086/375341. S2CID 59065632.
  113. ^ Napiwotzki, Ralf (2009). "The galactic population of white dwarfs". Journal of Physics. Conference Series. 172 (1): 012004. arXiv:0903.2159. Bibcode:2009JPhCS.172a2004N. doi:10.1088/1742-6596/172/1/012004. S2CID 17521113.
  114. ^ Laughlin, G.; Bodenheimer, P.; Adams, Fred C. (1997). "The End of the Main Sequence". The Astrophysical Journal. 482 (1): 420–432. Bibcode:1997ApJ...482..420L. doi:10.1086/304125.
  115. ^ a b Jeffery, Simon. . Archived from the original on 4 April 2015. Retrieved 3 May 2007.
  116. ^ Sarna, M. J.; Ergma, E.; Gerškevitš, J. (2001). "Helium core white dwarf evolution – including white dwarf companions to neutron stars". Astronomische Nachrichten. 322 (5–6): 405–410. Bibcode:2001AN....322..405S. doi:10.1002/1521-3994(200112)322:5/6<405::AID-ASNA405>3.0.CO;2-6.
  117. ^ Benvenuto, O. G.; De Vito, M. A. (2005). "The formation of helium white dwarfs in close binary systems – II". Monthly Notices of the Royal Astronomical Society. 362 (3): 891–905. Bibcode:2005MNRAS.362..891B. doi:10.1111/j.1365-2966.2005.09315.x.
  118. ^ Nelemans, G.; Tauris, T. M. (1998). "Formation of undermassive single white dwarfs and the influence of planets on late stellar evolution". Astronomy and Astrophysics. 335: L85. arXiv:astro-ph/9806011. Bibcode:1998A&A...335L..85N.
  119. ^ "Planet diet helps white dwarfs stay young and trim". New Scientist. No. 2639. 18 January 2008. from the original on 20 April 2010. Retrieved 18 September 2017.
  120. ^ Dhillon, Vik. . lecture notes, Physics 213. University of Sheffield. Archived from the original on 7 November 2012. Retrieved 3 May 2007.
  121. ^ Dhillon, Vik. . lecture notes, Physics 213. University of Sheffield. Archived from the original on 7 November 2012. Retrieved 3 May 2007.
  122. ^ Schaffner-Bielich, Jürgen (2005). "Strange quark matter in stars: A general overview". Journal of Physics G: Nuclear and Particle Physics. 31 (6): S651–S657. arXiv:astro-ph/0412215. Bibcode:2005JPhG...31S.651S. doi:10.1088/0954-3899/31/6/004. S2CID 118886040.
  123. ^ Nomoto, K. (1984). "Evolution of 8–10 solar mass stars toward electron capture supernovae. I – Formation of electron-degenerate O + NE + MG cores". The Astrophysical Journal. 277: 791. Bibcode:1984ApJ...277..791N. doi:10.1086/161749.
  124. ^ Woosley, S. E.; Heger, A.; Weaver, T. A. (2002). "The evolution and explosion of massive stars". Reviews of Modern Physics. 74 (4): 1015–1071. Bibcode:2002RvMP...74.1015W. doi:10.1103/RevModPhys.74.1015.
  125. ^ Werner, K.; Rauch, T.; Barstow, M. A.; Kruk, J. W. (2004). "Chandra and FUSE spectroscopy of the hot bare stellar core H?1504+65". Astronomy and Astrophysics. 421 (3): 1169–1183. arXiv:astro-ph/0404325. Bibcode:2004A&A...421.1169W. doi:10.1051/0004-6361:20047154. S2CID 2983893.
  126. ^ Livio, Mario; Truran, James W. (1994). "On the interpretation and implications of nova abundances: An abundance of riches or an overabundance of enrichments". The Astrophysical Journal. 425: 797. Bibcode:1994ApJ...425..797L. doi:10.1086/174024.
  127. ^ Jordan, George C. IV.; Perets, Hagai B.; Fisher, Robert T.; van Rossum, Daniel R. (2012). "Failed-detonation Supernovae: Subluminous Low-velocity Ia Supernovae and their Kicked Remnant White Dwarfs with Iron-rich Cores". The Astrophysical Journal Letters. 761 (2): L23. arXiv:1208.5069. Bibcode:2012ApJ...761L..23J. doi:10.1088/2041-8205/761/2/L23. S2CID 119203015.
  128. ^ Panei, J. A.; Althaus, L. G.; Benvenuto, O. G. (2000). "The evolution of iron-core white dwarfs". Monthly Notices of the Royal Astronomical Society. 312 (3): 531–539. arXiv:astro-ph/9911371. Bibcode:2000MNRAS.312..531P. doi:10.1046/j.1365-8711.2000.03236.x. S2CID 17854858.
  129. ^ a b c Adams, Fred C.; Laughlin, Gregory (1997). "A dying universe: The long-term fate and evolution of astrophysical objects". Reviews of Modern Physics. 69 (2): 337–372. arXiv:astro-ph/9701131. Bibcode:1997RvMP...69..337A. doi:10.1103/RevModPhys.69.337. S2CID 12173790.
  130. ^ Seager, S.; Kuchner, M.; Hier-Majumder, C.; Militzer, B. (19 July 2007). "Mass-Radius Relationships for Solid Exoplanets". The Astrophysical Journal (published November 2007). 669 (2): 1279–1297. arXiv:0707.2895. Bibcode:2007ApJ...669.1279S. doi:10.1086/521346. S2CID 8369390.
  131. ^ Lemonick, Michael (26 August 2011). . Time Magazine. Archived from the original on 24 August 2013. Retrieved 18 June 2015.
  132. ^ "Hubble finds dead stars "polluted" with planetary debris". ESA/Hubble Press Release. from the original on 9 June 2013. Retrieved 10 May 2013.
  133. ^ "Comet falling into white dwarf (artist's impression)". www.spacetelescope.org. from the original on 15 February 2017. Retrieved 14 February 2017.
  134. ^ Koester, D.; Gänsicke, B. T.; Farihi, J. (1 June 2014). "The frequency of planetary debris around young white dwarfs". Astronomy and Astrophysics. 566: A34. arXiv:1404.2617. Bibcode:2014A&A...566A..34K. doi:10.1051/0004-6361/201423691. ISSN 0004-6361. S2CID 119268896.
  135. ^ Jura, M. (1 May 2008). "Pollution of Single White Dwarfs by Accretion of Many Small Asteroids". The Astronomical Journal. 135 (5): 1785–1792. arXiv:0802.4075. Bibcode:2008AJ....135.1785J. doi:10.1088/0004-6256/135/5/1785. ISSN 0004-6256. S2CID 16571761.
  136. ^ a b c Debes, John H.; Thévenot, Melina; Kuchner, Marc J.; Burgasser, Adam J.; Schneider, Adam C.; Meisner, Aaron M.; Gagné, Jonathan; Faherty, Jacqueline K.; Rees, Jon M. (19 February 2019). "A 3 Gyr White Dwarf with Warm Dust Discovered via the Backyard Worlds: Planet 9 Citizen Science Project". The Astrophysical Journal. 872 (2): L25. arXiv:1902.07073. Bibcode:2019ApJ...872L..25D. doi:10.3847/2041-8213/ab0426. ISSN 2041-8213. S2CID 119359995.
  137. ^ van Maanen, A. (1 December 1917). "Two Faint Stars with Large Proper Motion". Publications of the Astronomical Society of the Pacific. 29 (172): 258. Bibcode:1917PASP...29..258V. doi:10.1086/122654. ISSN 0004-6280. S2CID 250734202.
  138. ^ a b Klein, Beth L.; Doyle, Alexandra E.; Zuckerman, B.; Dufour, P.; Blouin, Simon; Melis, Carl; Weinberger, Alycia J.; Young, Edward D. (1 June 2021). "Discovery of Beryllium in White Dwarfs Polluted by Planetesimal Accretion". The Astrophysical Journal. 914 (1): 61. arXiv:2102.01834. Bibcode:2021ApJ...914...61K. doi:10.3847/1538-4357/abe40b. ISSN 0004-637X. S2CID 231786441.
  139. ^ Zuckerman, B. (1 June 2015). Recognition of the First Observational Evidence of an Extrasolar Planetary System. 19Th European Workshop on White Dwarfs. Vol. 493. p. 291. Bibcode:2015ASPC..493..291Z.
  140. ^ Farihi, J. (1 April 2016). "Circumstellar debris and pollution at white dwarf stars". New Astronomy Reviews. 71: 9–34. arXiv:1604.03092. Bibcode:2016NewAR..71....9F. doi:10.1016/j.newar.2016.03.001. ISSN 1387-6473. S2CID 118486264.
  141. ^ Zuckerman, B.; Becklin, E. E. (1 November 1987). "Excess infrared radiation from a white dwarf—an orbiting brown dwarf?". Nature. 330 (6144): 138–140. Bibcode:1987Natur.330..138Z. doi:10.1038/330138a0. ISSN 0028-0836. S2CID 4357883.
  142. ^ a b Reach, William T.; Kuchner, Marc J.; Von Hippel, Ted; Burrows, Adam; Mullally, Fergal; Kilic, Mukremin; Winget, D. E. (2005). "The Dust Cloud around the White Dwarf G29-38". The Astrophysical Journal. 635 (2): L161. arXiv:astro-ph/0511358. Bibcode:2005ApJ...635L.161R. doi:10.1086/499561. S2CID 119462589.
  143. ^ Steckloff, Jordan K.; Debes, John; Steele, Amy; Johnson, Brandon; Adams, Elisabeth R.; Jacobson, Seth A.; Springmann, Alessondra (1 June 2021). "How Sublimation Delays the Onset of Dusty Debris Disk Formation around White Dwarf Stars". The Astrophysical Journal. 913 (2): L31. arXiv:2104.14035. Bibcode:2021ApJ...913L..31S. doi:10.3847/2041-8213/abfd39. ISSN 0004-637X. PMC 8740607. PMID 35003618.
  144. ^ a b Veras, Dimitri (1 October 2021). Planetary Systems Around White Dwarfs. Bibcode:2021orel.bookE...1V.
  145. ^ Sanderson, Hannah; Bonsor, Amy; Mustill, Alexander J (1 June 2022). "The galactic population of white dwarfs". Journal of Physics: Conference Series. 172 (1): 012004. arXiv:0903.2159. Bibcode:2009JPhCS.172a2004N. doi:10.1088/1742-6596/172/1/012004. S2CID 250666952.
  146. ^ Mullally, Susan Elizabeth; Mullally, Fergal; Albert, Loic; Barclay, Thomas; Debes, John Henry; Kilic, Mukremin; Kuchner, Marc Jason; Quintana, Elisa V.; Reach, William (2021). "A Search for the Giant Planets that Drive White Dwarf Accretion". JWST Proposal. Cycle 1: 1911. Bibcode:2021jwst.prop.1911M.
  147. ^ . BBC News. 13 February 2007. Archived from the original on 16 February 2007. Retrieved 20 September 2007.
  148. ^ Su, K. Y. L.; Chu, Y.-H.; Rieke, G. H.; Huggins, P. J.; Gruendl, R.; Napiwotzki, R.; Rauch, T.; Latter, W. B.; Volk, K. (2007). "A Debris Disk around the Central Star of the Helix Nebula?". The Astrophysical Journal. 657 (1): L41. arXiv:astro-ph/0702296. Bibcode:2007ApJ...657L..41S. doi:10.1086/513018. S2CID 15244406.
  149. ^ Sion, Edward M.; Holberg, J.B.; Oswalt, Terry D.; McCook, George P.; Wasatonic, Richard (2009). "The White Dwarfs Within 20 Parsecs of the Sun: Kinematics and Statistics". The Astronomical Journal. 138 (6): 1681–1689. arXiv:0910.1288. Bibcode:2009AJ....138.1681S. doi:10.1088/0004-6256/138/6/1681. S2CID 119284418.
  150. ^ Li, Jianke; Ferrario, Lilia; Wickramasinghe, Dayal (1998). "Planets around White Dwarfs". Astrophysical Journal Letters. 503 (1): L151. Bibcode:1998ApJ...503L.151L. doi:10.1086/311546. p. L51.
  151. ^ Debes, John H.; Walsh, Kevin J.; Stark, Christopher (24 February 2012). "The Link Between Planetary Systems, Dusty White Dwarfs, and Metal-Polluted White Dwarfs". The Astrophysical Journal. 747 (2): 148. arXiv:1201.0756. Bibcode:2012ApJ...747..148D. doi:10.1088/0004-637X/747/2/148. ISSN 0004-637X. S2CID 118688656.
  152. ^ Veras, Dimitri; Gänsicke, Boris T. (21 February 2015). "Detectable close-in planets around white dwarfs through late unpacking". Monthly Notices of the Royal Astronomical Society. 447 (2): 1049–1058. arXiv:1411.6012. Bibcode:2015MNRAS.447.1049V. doi:10.1093/mnras/stu2475. ISSN 0035-8711. S2CID 119279872.
  153. ^ Frewen, S. F. N.; Hansen, B. M. S. (11 April 2014). "Eccentric planets and stellar evolution as a cause of polluted white dwarfs". Monthly Notices of the Royal Astronomical Society. 439 (3): 2442–2458. arXiv:1401.5470. Bibcode:2014MNRAS.439.2442F. doi:10.1093/mnras/stu097. ISSN 0035-8711. S2CID 119257046.
  154. ^ Bonsor, Amy; Gänsicke, Boris T.; Veras, Dimitri; Villaver, Eva; Mustill, Alexander J. (21 May 2018). "Unstable low-mass planetary systems as drivers of white dwarf pollution". Monthly Notices of the Royal Astronomical Society. 476 (3): 3939–3955. arXiv:1711.02940. Bibcode:2018MNRAS.476.3939M. doi:10.1093/mnras/sty446. ISSN 0035-8711. S2CID 4809366.
  155. ^ Gänsicke, Boris T.; Holman, Matthew J.; Veras, Dimitri; Payne, Matthew J. (21 March 2016). "Liberating exomoons in white dwarf planetary systems". Monthly Notices of the Royal Astronomical Society. 457 (1): 217–231. arXiv:1603.09344. Bibcode:2016MNRAS.457..217P. doi:10.1093/mnras/stv2966. ISSN 0035-8711. S2CID 56091285.
  156. ^ Rebassa-Mansergas, Alberto; Xu (许偲艺), Siyi; Veras, Dimitri (21 January 2018). "The critical binary star separation for a planetary system origin of white dwarf pollution". Monthly Notices of the Royal Astronomical Society. 473 (3): 2871–2880. arXiv:1708.05391. Bibcode:2018MNRAS.473.2871V. doi:10.1093/mnras/stx2141. ISSN 0035-8711. S2CID 55764122.
  157. ^ Becklin, E. E.; Zuckerman, B.; Farihi, J. (10 February 2008). "Spitzer IRAC Observations of White Dwarfs. I. Warm Dust at Metal-Rich Degenerates". The Astrophysical Journal. 674 (1): 431–446. arXiv:0710.0907. Bibcode:2008ApJ...674..431F. doi:10.1086/521715. ISSN 0004-637X. S2CID 17813180.
  158. ^ Sigurdsson, Steinn; Richer, Harvey B.; Hansen, Brad M.; Stairs, Ingrid H.; Thorsett, Stephen E. (1 July 2003). "A Young White Dwarf Companion to Pulsar B1620-26: Evidence for Early Planet Formation". Science. 301 (5630): 193–196. arXiv:astro-ph/0307339. Bibcode:2003Sci...301..193S. doi:10.1126/science.1086326. ISSN 0036-8075. PMID 12855802. S2CID 39446560.
  159. ^ Hardy, Adam; Schreiber, Matthias R.; Parsons, Steven G.; Caceres, Claudio; Brinkworth, Carolyn; Veras, Dimitri; Gänsicke, Boris T.; Marsh, Thomas R.; Cieza, Lucas (1 July 2016). "The detection of dust around NN Ser". Monthly Notices of the Royal Astronomical Society. 459 (4): 4518–4526. arXiv:1604.05808. Bibcode:2016MNRAS.459.4518H. doi:10.1093/mnras/stw976. ISSN 0035-8711.
  160. ^ Beuermann, K.; Hessman, F. V.; Dreizler, S.; Marsh, T. R.; Parsons, S. G.; Winget, D. E.; Miller, G. F.; Schreiber, M. R.; Kley, W.; Dhillon, V. S.; Littlefair, S. P.; Copperwheat, C. M.; Hermes, J. J. (1 October 2010). "Two planets orbiting the recently formed post-common envelope binary NN Serpentis". Astronomy and Astrophysics. 521: L60. arXiv:1010.3608. Bibcode:2010A&A...521L..60B. doi:10.1051/0004-6361/201015472. ISSN 0004-6361. S2CID 53702506.
  161. ^ Luhman, K. L.; Burgasser, A. J.; Bochanski, J. J. (1 March 2011). "Discovery of a Candidate for the Coolest Known Brown Dwarf". The Astrophysical Journal. 730 (1): L9. arXiv:1102.5411. Bibcode:2011ApJ...730L...9L. doi:10.1088/2041-8205/730/1/L9. hdl:1721.1/95646. ISSN 0004-637X. S2CID 54666396.
  162. ^ Leggett, S. K.; Tremblin, P.; Esplin, T. L.; Luhman, K. L.; Morley, Caroline V. (1 June 2017). "The Y-type Brown Dwarfs: Estimates of Mass and Age from New Astrometry, Homogenized Photometry, and Near-infrared Spectroscopy". The Astrophysical Journal. 842 (2): 118. arXiv:1704.03573. Bibcode:2017ApJ...842..118L. doi:10.3847/1538-4357/aa6fb5. ISSN 0004-637X. S2CID 119249195.
  163. ^ a b Gänsicke, Boris T.; Schreiber, Matthias R.; Toloza, Odette; Gentile Fusillo, Nicola P.; Koester, Detlev; Manser, Christopher J. "Accretion of a giant planet onto a white dwarf" (PDF). ESO. (PDF) from the original on 4 December 2019. Retrieved 11 December 2019.
  164. ^ Xu, Siyi; Diamond-Lowe, Hannah; MacDonald, Ryan J.; Vanderburg, Andrew; Blouin, Simon; Dufour, P.; Gao, Peter; Kreidberg, Laura; Leggett, S. K.; Mann, Andrew W.; Morley, Caroline V.; Stephens, Andrew W.; O'Connor, Christopher E.; Thao, Pa Chia; Lewis, Nikole K. (1 December 2021). "Gemini/GMOS Transmission Spectroscopy of the Grazing Planet Candidate WD 1856+534 b". The Astronomical Journal. 162 (6): 296. arXiv:2110.14106. Bibcode:2021AJ....162..296X. doi:10.3847/1538-3881/ac2d26. ISSN 0004-6256. S2CID 239998664.
  165. ^ Vanderburg, Andrew; et al. (16 September 2020). "A giant planet candidate transiting a white dwarf". Nature. 585 (7825): 363–367. arXiv:2009.07282. Bibcode:2020Natur.585..363V. doi:10.1038/s41586-020-2713-y. hdl:1721.1/129733. PMID 32939071. S2CID 221738865.
  166. ^ Chou, Felicia; Andreoli, Claire; Cofield, Calia (16 September 2020). "NASA Missions Spy First Possible Planet Hugging a Stellar Cinder". NASA.
  167. ^ Gary, Bruce L. (17 September 2020). "WD 1856+534 Transit Light Curve Photometry". BruceGary.net. Retrieved 17 September 2020.
  168. ^ Rappaport, S.; Gary, B. L.; Vanderburg, A.; Xu, S.; Pooley, D.; Mukai, K. (1 February 2018). "WD 1145+017: optical activity during 2016-2017 and limits on the X-ray flux". Monthly Notices of the Royal Astronomical Society. 474 (1): 933–946. arXiv:1709.08195. Bibcode:2018MNRAS.474..933R. doi:10.1093/mnras/stx2663. ISSN 0035-8711.
  169. ^ a b c d Vanderburg, Andrew; Johnson, John Asher; Rappaport, Saul; Bieryla, Allyson; Irwin, Jonathan; Lewis, John Arban; Kipping, David; Brown, Warren R.; Dufour, Patrick (22 October 2015). "A disintegrating minor planet transiting a white dwarf". Nature. 526 (7574): 546–549. arXiv:1510.06387. Bibcode:2015Natur.526..546V. doi:10.1038/nature15527. PMID 26490620. S2CID 4451207.
  170. ^ Manser, Christopher J.; Gänsicke, Boris T.; Eggl, Siegfried; Hollands, Mark; Izquierdo, Paula; Koester, Detlev; Landstreet, John D.; Lyra, Wladimir; Marsh, Thomas R.; Meru, Farzana; Mustill, Alexander J.; Rodríguez-Gil, Pablo; Toloza, Odette; Veras, Dimitri; Wilson, David J. (1 April 2019). "A planetesimal orbiting within the debris disc around a white dwarf star". Science. 364 (6435): 66–69. arXiv:1904.02163. Bibcode:2019Sci...364...66M. doi:10.1126/science.aat5330. ISSN 0036-8075. PMID 30948547. S2CID 96434522.
  171. ^ Swan, Andrew; Kenyon, Scott J.; Farihi, Jay; Dennihy, Erik; Gänsicke, Boris T.; Hermes, J. J.; Melis, Carl; von Hippel, Ted (1 September 2021). "Collisions in a gas-rich white dwarf planetary debris disc". Monthly Notices of the Royal Astronomical Society. 506 (1): 432–440. arXiv:2106.09025. Bibcode:2021MNRAS.506..432S. doi:10.1093/mnras/stab1738. ISSN 0035-8711. PMC 8263348. PMID 34248393.
  172. ^ a b Wang, Ting-Gui; Jiang, Ning; Ge, Jian; Cutri, Roc M.; Jiang, Peng; Sheng, Zhengfeng; Zhou, Hongyan; Bauer, James; Mainzer, Amy; Wright, Edward L. (9 October 2019). "An On-going Mid-infrared Outburst in the White Dwarf 0145+234: Catching in Action of Tidal Disruption of an Exoasteroid?". arXiv:1910.04314 [astro-ph.SR].
  173. ^ Vanderbosch, Z.; Hermes, J. J.; Dennihy, E.; Dunlap, B. H.; Izquierdo, P.; Tremblay, P. -E.; Cho, P. B.; Gänsicke, B. T.; Toloza, O.; Bell, K. J.; Montgomery, M. H.; Winget, D. E. (1 July 2020). "A White Dwarf with Transiting Circumstellar Material Far outside the Roche Limit". The Astrophysical Journal. 897 (2): 171. arXiv:1908.09839. Bibcode:2020ApJ...897..171V. doi:10.3847/1538-4357/ab9649. ISSN 0004-637X. S2CID 219941489.
  174. ^ Veras, Dimitri; McDonald, Catriona H.; Makarov, Valeri V. (1 March 2020). "Constraining the origin of the planetary debris surrounding ZTF J0139+5245 through rotational fission of a triaxial asteroid". Monthly Notices of the Royal Astronomical Society. 492 (4): 5291–5296. arXiv:2001.08223. Bibcode:2020MNRAS.492.5291V. doi:10.1093/mnras/staa243. ISSN 0035-8711.
  175. ^ Guidry, Joseph A.; Vanderbosch, Zachary P.; Hermes, J. J.; Barlow, Brad N.; Lopez, Isaac D.; Boudreaux, Thomas M.; Corcoran, Kyle A.; Bell, Keaton J.; Montgomery, M. H.; Heintz, Tyler M.; Castanheira, Barbara G.; Reding, Joshua S.; Dunlap, Bart H.; Winget, D. E.; Winget, Karen I. (1 May 2021). "I Spy Transits and Pulsations: Empirical Variability in White Dwarfs Using Gaia and the Zwicky Transient Facility". The Astrophysical Journal. 912 (2): 125. arXiv:2012.00035. Bibcode:2021ApJ...912..125G. doi:10.3847/1538-4357/abee68. ISSN 0004-637X. S2CID 227238802.
  176. ^ Vanderbosch, Zachary P.; Rappaport, Saul; Guidry, Joseph A.; Gary, Bruce L.; Blouin, Simon; Kaye, Thomas G.; Weinberger, Alycia J.; Melis, Carl; Klein, Beth L.; Zuckerman, B.; Vanderburg, Andrew; Hermes, J. J.; Hegedus, Ryan J.; Burleigh, Matthew. R.; Sefako, Ramotholo (1 August 2021). "Recurring Planetary Debris Transits and Circumstellar Gas around White Dwarf ZTF J0328-1219". The Astrophysical Journal. 917 (1): 41. arXiv:2106.02659. Bibcode:2021ApJ...917...41V. doi:10.3847/1538-4357/ac0822. ISSN 0004-637X. S2CID 235358242.
  177. ^ Lemonick, Michael D. (21 October 2015). "Zombie Star Caught Feasting on Asteroids". National Geographic News. from the original on 24 October 2015. Retrieved 22 October 2015.
  178. ^ Agol, Eric (2011). "Transit Surveys for Earths in the Habitable Zones of White Dwarfs". The Astrophysical Journal Letters. 635 (2): L31. arXiv:1103.2791. Bibcode:2011ApJ...731L..31A. doi:10.1088/2041-8205/731/2/L31. S2CID 118739494.
  179. ^ Barnes, Rory; Heller, René (2011). "Habitable Planets Around White and Brown Dwarfs: The Perils of a Cooling Primary". Astrobiology. 13 (3): 279–291. arXiv:1211.6467. Bibcode:2013AsBio..13..279B. doi:10.1089/ast.2012.0867. PMC 3612282. PMID 23537137.
  180. ^ Nordhaus, J.; Spiegel, D.S. (2013). "On the orbits of low-mass companions to white dwarfs and the fates of the known exoplanets". Monthly Notices of the Royal Astronomical Society. 432 (1): 500–505. arXiv:1211.1013. Bibcode:2013MNRAS.432..500N. doi:10.1093/mnras/stt569. S2CID 119227364.
  181. ^ Di Stefano, R.; Nelson, L. A.; Lee, W.; Wood, T. H.; Rappaport, S. (1997). "Luminous Supersoft X-ray Sources as Type Ia Progenitors". In P. Ruiz-Lapuente; R. Canal; J. Isern (eds.). Thermonuclear supernovae. Nato Advanced Science Institutes (Asi) Series C. NATO ASI series: Mathematical and physical sciences. Vol. 486. Springer. pp. 148–149. Bibcode:1997ASIC..486..147D. doi:10.1007/978-94-011-5710-0_10. ISBN 978-0-7923-4359-2.
  182. ^ Lopes de Oliveira, R.; Bruch, A.; Rodrigues, C. V.; de Oliveira, A. S.; Mukai, K. (2020). "CTCV J2056-3014: An X-Ray-faint Intermediate Polar Harboring an Extremely Fast-spinning White Dwarf". The Astrophysical Journal Letters. 898 (2): L40. arXiv:2007.13932. Bibcode:2020ApJ...898L..40L. doi:10.3847/2041-8213/aba618. S2CID 220831174.
  183. ^ Aguilar, David A.; Pulliam, Christine (16 November 2010). "Astronomers Discover Merging Star Systems that Might Explode". Harvard-Smithsonian Center for Astrophysics. from the original on 9 April 2011. Retrieved 16 February 2011.
  184. ^ Aguilar, David A.; Pulliam, Christine (13 July 2011). "Evolved Stars Locked in Fatalistic Dance". Harvard-Smithsonian Center for Astrophysics. from the original on 15 July 2011. Retrieved 17 July 2011.
  185. ^ Yoon, S.-C.; Langer, N. (2004). "Presupernova evolution of accreting white dwarfs with rotation". Astronomy and Astrophysics. 419 (2): 623–644. arXiv:astro-ph/0402287. Bibcode:2004A&A...419..623Y. doi:10.1051/0004-6361:20035822. S2CID 2963085.
  186. ^ Blinnikov, S. I.; Röpke, F. K.; Sorokina, E. I.; Gieseler, M.; Reinecke, M.; Travaglio, C.; Hillebrandt, W.; Stritzinger, M. (2006). "Theoretical light curves for deflagration models of type Ia supernova". Astronomy and Astrophysics. 453 (1): 229–240. arXiv:astro-ph/0603036. Bibcode:2006A&A...453..229B. doi:10.1051/0004-6361:20054594. S2CID 15493284.
  187. ^ O'Neill, Ian (6 September 2011). . Discovery Communications, LLC. Archived from the original on 24 January 2012.
  188. ^ González Hernández, J.I.; Ruiz-Lapuente, P.; Tabernero, H. M.; Montes, D.; Canal, R.; Méndez, J.; Bedin, L. R. (2012). "No surviving evolved companions of the progenitor of SN 1006". Nature. 489 (7417): 533–536. arXiv:1210.1948. Bibcode:2012Natur.489..533G. doi:10.1038/nature11447. PMID 23018963. S2CID 4431391.
  189. ^ Krause, Oliver; et al. (2008). "Tycho Brahe's 1572 supernova as a standard type Ia as revealed by its light-echo spectrum". Nature. 456 (7222): 617–619. arXiv:0810.5106. Bibcode:2008Natur.456..617K. doi:10.1038/nature07608. PMID 19052622. S2CID 4409995.
  190. ^ de la Fuente Marcos, Raúl; de la Fuente Marcos, Carlos (2022). "Deep and fast Solar System flybys: The controversial case of WD 0810-353". Astronomy & Astrophysics. EDP Sciences. arXiv:2210.04863. Bibcode:2022arXiv221004863D. doi:10.1051/0004-6361/202245020. ISSN 0004-6361. S2CID 252863734.
  191. ^ . fact sheet. Imagine the Universe!. NASA Goddard. Archived from the original on 9 July 2007. Retrieved 4 May 2007.
  192. ^ a b "Introduction to Cataclysmic Variables (CVs)". fact sheet. NASA Goddard. from the original on 6 February 2012. Retrieved 4 May 2007.
  193. ^ Giammichele, N.; Bergeron, P.; Dufour, P. (April 2012). "Know Your Neighborhood: A Detailed Model Atmosphere Analysis of Nearby White Dwarfs". The Astrophysical Journal Supplement. 199 (2): 35. arXiv:1202.5581. Bibcode:2012ApJS..199...29G. doi:10.1088/0067-0049/199/2/29. S2CID 118304737. 29.
  194. ^ Delfosse, Xavier; et al. (April 1999). "New neighbours. I. 13 new companions to nearby M dwarfs". Astronomy and Astrophysics. 344: 897–910. arXiv:astro-ph/9812008. Bibcode:1999A&A...344..897D.
  195. ^ "Rocky Exoplanets Are Even Stranger Than We Thought". Retrieved 2 December 2021.
  196. ^ "Cosmic 'Spider' Found to Be Source of Powerful Gamma-Rays". Retrieved 13 December 2022.
  197. ^ "Citizen Scientist Leads Discovery of 34 Ultracool Dwarf Binaries Using Archive at NSF's NOIRLab". Retrieved 16 December 2022.

External links and further reading

 
Wikimedia Commons has media related to White dwarfs.

General

  • Kawaler, S. D. (1997). "White Dwarf Stars". In Kawaler, S. D.; Novikov, I.; Srinivasan, G. (eds.). Stellar remnants. 1997. ISBN 978-3-540-61520-0.
  • Kepler, S. O.; et al. (February 2015). "New white dwarf stars in the Sloan Digital Sky Survey Data Release 10". Monthly Notices of the Royal Astronomical Society. 446 (4): 4078–4087. arXiv:1411.4149. Bibcode:2015MNRAS.446.4078K. doi:10.1093/mnras/stu2388. ISSN 1365-2966.
  • Rebassa-Mansergas, A.; Gänsicke, B. T.; Rodríguez-Gil, P.; Schreiber, M. R.; Koester, D. (28 November 2007). "Post-common-envelope binaries from SDSS – I. 101 white dwarf main-sequence binaries with multiple Sloan Digital Sky Survey spectroscopy: Post-common-envelope binaries from SDSS". Monthly Notices of the Royal Astronomical Society. 382 (4): 1377–1393. doi:10.1111/j.1365-2966.2007.12288.x.

Physics

  • Black holes, white dwarfs, and neutron stars: the physics of compact objects, Stuart L. Shapiro and Saul A. Teukolsky, New York: Wiley, 1983. ISBN 0-471-87317-9.
  • Gentile, Dave (1995). White dwarf stars and the Chandrasekhar limit (Master's thesis). DePaul University.
  • "Estimating Stellar Parameters from Energy Equipartition". sciencebits.com. — Discusses how to find mass-radius relations and mass limits for white dwarfs using simple energy arguments.

Variability

  • Winget, D.E. (1998). "Asteroseismology of white dwarf stars". Journal of Physics: Condensed Matter. 10 (49): 11247–11261. Bibcode:1998JPCM...1011247W. doi:10.1088/0953-8984/10/49/014. S2CID 250749380.

Magnetic field

  • Wickramasinghe, D. T.; Ferrario, Lilia (2000). "Magnetism in Isolated and Binary White Dwarfs". Publications of the Astronomical Society of the Pacific. 112 (773): 873–924. Bibcode:2000PASP..112..873W. doi:10.1086/316593.

Frequency

  • Gibson, B. K.; Flynn, C (2001). "White Dwarfs and Dark Matter". Science. 292 (5525): 2211a. arXiv:astro-ph/0104255. doi:10.1126/science.292.5525.2211a. PMID 11423620. S2CID 14080941.

Observational

  • Provencal, J. L.; Shipman, H. L.; Hog, Erik; Thejll, P. (1998). "Testing the White Dwarf Mass-Radius Relation with Hipparcos". The Astrophysical Journal. 494 (2): 759–767. Bibcode:1998ApJ...494..759P. doi:10.1086/305238.
  • Gates, Evalyn; Gyuk, Geza; Harris, Hugh C.; Subbarao, Mark; Anderson, Scott; Kleinman, S. J.; Liebert, James; Brewington, Howard; et al. (2004). "Discovery of New Ultracool White Dwarfs in the Sloan Digital Sky Survey". The Astrophysical Journal. 612 (2): L129. arXiv:astro-ph/0405566. Bibcode:2004ApJ...612L.129G. doi:10.1086/424568. S2CID 7570539.
  • McCook, G.P.; Sion, E.M. (eds.). "White Dwarf Catalogue WD". Villanova University.
  • Dufour, P.; Liebert, James; Fontaine, G.; Behara, N. (2007). "White dwarf stars with carbon atmospheres". Nature. 450 (7169): 522–4. arXiv:0711.3227. Bibcode:2007Natur.450..522D. doi:10.1038/nature06318. PMID 18033290. S2CID 4398697.

Images

  • Astronomy Picture of the Day
    • NGC 2440: Cocoon of a New White Dwarf. Astronomy Picture of the Day (photograph). NASA. 21 February 2010.
    • Dust and the Helix Nebula. Astronomy Picture of the Day (photograph). NASA. 31 December 2009.
    • The Helix Nebula from La Silla Observatory. Astronomy Picture of the Day (photograph). NASA. 3 March 2009.
    • IC 4406: A Seemingly Square Nebula. Astronomy Picture of the Day (photograph). NASA. 27 July 2008.
    • A Nearby Supernova in Spiral Galaxy M100. Astronomy Picture of the Day (photograph). NASA. 7 March 2006.
    • White Dwarf Star Spiral. Astronomy Picture of the Day (photograph). NASA. 1 June 2005.

January 10, 2023
white, dwarf, other, uses, disambiguation, degenerate, dwarf, redirects, here, confused, with, degenerate, star, white, dwarf, stellar, core, remnant, composed, mostly, electron, degenerate, matter, white, dwarf, very, dense, mass, comparable, while, volume, c. For other uses see White dwarf disambiguation Degenerate dwarf redirects here Not to be confused with Degenerate star A white dwarf is a stellar core remnant composed mostly of electron degenerate matter A white dwarf is very dense its mass is comparable to the Sun s while its volume is comparable to the Earth s A white dwarf s faint luminosity comes from the emission of residual thermal energy no fusion takes place in a white dwarf 1 The nearest known white dwarf is Sirius B at 8 6 light years the smaller component of the Sirius binary star There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun 2 The unusual faintness of white dwarfs was first recognized in 1910 3 1 The name white dwarf was coined by Willem Luyten in 1922 Image of Sirius A and Sirius B taken by the Hubble Space Telescope Sirius B which is a white dwarf can be seen as a faint point of light to the lower left of the much brighter Sirius A White dwarfs are thought to be the final evolutionary state of stars whose mass is not high enough to become a neutron star or black hole This includes over 97 of the other stars in the Milky Way 4 1 After the hydrogen fusing period of a main sequence star of low or medium mass ends such a star will expand to a red giant during which it fuses helium to carbon and oxygen in its core by the triple alpha process If a red giant has insufficient mass to generate the core temperatures required to fuse carbon around 1 billion K an inert mass of carbon and oxygen will build up at its center After such a star sheds its outer layers and forms a planetary nebula it will leave behind a core which is the remnant white dwarf 5 Usually white dwarfs are composed of carbon and oxygen CO white dwarf If the mass of the progenitor is between 8 and 10 5 solar masses M the core temperature will be sufficient to fuse carbon but not neon in which case an oxygen neon magnesium ONeMg or ONe white dwarf may form 6 Stars of very low mass will be unable to fuse helium hence a helium white dwarf 7 8 may form by mass loss in binary systems The material in a white dwarf no longer undergoes fusion reactions so the star has no source of energy As a result it cannot support itself by the heat generated by fusion against gravitational collapse but is supported only by electron degeneracy pressure causing it to be extremely dense The physics of degeneracy yields a maximum mass for a non rotating white dwarf the Chandrasekhar limit approximately 1 44 times M beyond which it cannot be supported by electron degeneracy pressure A carbon oxygen white dwarf that approaches this mass limit typically by mass transfer from a companion star may explode as a type Ia supernova via a process known as carbon detonation 1 5 SN 1006 is thought to be a famous example A white dwarf is very hot when it forms but because it has no source of energy it will gradually cool as it radiates its energy away This means that its radiation which initially has a high color temperature will lessen and redden with time Over a very long time a white dwarf will cool and its material will begin to crystallize starting with the core The star s low temperature means it will no longer emit significant heat or light and it will become a cold black dwarf 5 Because the length of time it takes for a white dwarf to reach this state is calculated to be longer than the current age of the known universe approximately 13 8 billion years 9 it is thought that no black dwarfs yet exist 1 4 The oldest known white dwarfs still radiate at temperatures of a few thousand kelvins which establishes an observational limit on the maximum possible age of the universe 10 Contents 1 Discovery 2 Composition and structure 2 1 Mass radius relationship 2 2 Radiation and cooling 2 3 Atmosphere and spectra 2 3 1 Metal rich white dwarfs 2 4 Magnetic field 2 4 1 Chemical bonds 3 Variability 4 Formation 4 1 Stars with very low mass 4 2 Stars with low to medium mass 4 3 Stars with medium to high mass 4 4 Type Iax supernova 5 Fate 6 Debris disks and planets 7 Habitability 8 Binary stars and novae 8 1 Type Ia supernovae 8 2 Post common envelope binary 8 3 Cataclysmic variables 8 4 Other non pre supernova binaries 9 Nearest 10 Gallery 11 See also 12 References 13 External links and further readingDiscovery EditSee also List of white dwarfs The first white dwarf discovered was in the triple star system of 40 Eridani which contains the relatively bright main sequence star 40 Eridani A orbited at a distance by the closer binary system of the white dwarf 40 Eridani B and the main sequence red dwarf 40 Eridani C The pair 40 Eridani B C was discovered by William Herschel on 31 January 1783 11 In 1910 Henry Norris Russell Edward Charles Pickering and Williamina Fleming discovered that despite being a dim star 40 Eridani B was of spectral type A or white 12 In 1939 Russell looked back on the discovery 3 1 I was visiting my friend and generous benefactor Prof Edward C Pickering With characteristic kindness he had volunteered to have the spectra observed for all the stars including comparison stars which had been observed in the observations for stellar parallax which Hinks and I made at Cambridge and I discussed This piece of apparently routine work proved very fruitful it led to the discovery that all the stars of very faint absolute magnitude were of spectral class M In conversation on this subject as I recall it I asked Pickering about certain other faint stars not on my list mentioning in particular 40 Eridani B Characteristically he sent a note to the Observatory office and before long the answer came I think from Mrs Fleming that the spectrum of this star was A I knew enough about it even in these paleozoic days to realize at once that there was an extreme inconsistency between what we would then have called possible values of the surface brightness and density I must have shown that I was not only puzzled but crestfallen at this exception to what looked like a very pretty rule of stellar characteristics but Pickering smiled upon me and said It is just these exceptions that lead to an advance in our knowledge and so the white dwarfs entered the realm of study The spectral type of 40 Eridani B was officially described in 1914 by Walter Adams 13 The white dwarf companion of Sirius Sirius B was next to be discovered During the nineteenth century positional measurements of some stars became precise enough to measure small changes in their location Friedrich Bessel used position measurements to determine that the stars Sirius a Canis Majoris and Procyon a Canis Minoris were changing their positions periodically In 1844 he predicted that both stars had unseen companions 14 If we were to regard Sirius and Procyon as double stars the change of their motions would not surprise us we should acknowledge them as necessary and have only to investigate their amount by observation But light is no real property of mass The existence of numberless visible stars can prove nothing against the existence of numberless invisible ones Bessel roughly estimated the period of the companion of Sirius to be about half a century 14 C A F Peters computed an orbit for it in 1851 15 It was not until 31 January 1862 that Alvan Graham Clark observed a previously unseen star close to Sirius later identified as the predicted companion 15 Walter Adams announced in 1915 that he had found the spectrum of Sirius B to be similar to that of Sirius 16 In 1917 Adriaan van Maanen discovered van Maanen s Star an isolated white dwarf 17 These three white dwarfs the first discovered are the so called classical white dwarfs 3 2 Eventually many faint white stars were found which had high proper motion indicating that they could be suspected to be low luminosity stars close to the Earth and hence white dwarfs Willem Luyten appears to have been the first to use the term white dwarf when he examined this class of stars in 1922 12 18 19 20 21 the term was later popularized by Arthur Stanley Eddington 12 22 Despite these suspicions the first non classical white dwarf was not definitely identified until the 1930s 18 white dwarfs had been discovered by 1939 3 3 Luyten and others continued to search for white dwarfs in the 1940s By 1950 over a hundred were known 23 and by 1999 over 2 000 were known 24 Since then the Sloan Digital Sky Survey has found over 9 000 white dwarfs mostly new 25 Composition and structure Edit Hertzsprung Russell diagram Spectral type O B A F G K M L T Brown dwarfs White dwarfs Red dwarfs Subdwarfs Main sequence dwarfs Subgiants Giants Red giants Blue giants Bright giants Supergiants Red supergiant Hypergiants absolutemagni tude MV Although white dwarfs are known with estimated masses as low as 0 17 M 26 and as high as 1 33 M 27 the mass distribution is strongly peaked at 0 6 M and the majority lie between 0 5 and 0 7 M 27 The estimated radii of observed white dwarfs are typically 0 8 2 the radius of the Sun 28 this is comparable to the Earth s radius of approximately 0 9 solar radius A white dwarf then packs mass comparable to the Sun s into a volume that is typically a million times smaller than the Sun s the average density of matter in a white dwarf must therefore be very roughly 1 000 000 times greater than the average density of the Sun or approximately 106 g cm3 or 1 tonne per cubic centimetre 1 A typical white dwarf has a density of between 104 and 107 g cm3 White dwarfs are composed of one of the densest forms of matter known surpassed only by other compact stars such as neutron stars quark stars hypothetical 29 and black holes White dwarfs were found to be extremely dense soon after their discovery If a star is in a binary system as is the case for Sirius B or 40 Eridani B it is possible to estimate its mass from observations of the binary orbit This was done for Sirius B by 1910 30 yielding a mass estimate of 0 94 M which compares well with a more modern estimate of 1 00 M 31 Since hotter bodies radiate more energy than colder ones a star s surface brightness can be estimated from its effective surface temperature and that from its spectrum If the star s distance is known its absolute luminosity can also be estimated From the absolute luminosity and distance the star s surface area and its radius can be calculated Reasoning of this sort led to the realization puzzling to astronomers at the time that due to their relatively high temperature and relatively low absolute luminosity Sirius B and 40 Eridani B must be very dense When Ernst Opik estimated the density of a number of visual binary stars in 1916 he found that 40 Eridani B had a density of over 25 000 times the Sun s which was so high that he called it impossible 32 As A S Eddington put it later in 1927 33 50 We learn about the stars by receiving and interpreting the messages which their light brings to us The message of the companion of Sirius when it was decoded ran I am composed of material 3 000 times denser than anything you have ever come across a ton of my material would be a little nugget that you could put in a matchbox What reply can one make to such a message The reply which most of us made in 1914 was Shut up Don t talk nonsense As Eddington pointed out in 1924 densities of this order implied that according to the theory of general relativity the light from Sirius B should be gravitationally redshifted 22 This was confirmed when Adams measured this redshift in 1925 34 Material Density in kg m3 NotesSupermassive black hole c 1 000 35 Critical density of a black hole of around 108 solar masses Water fresh 1 000 At STPOsmium 22 610 Near room temperatureThe core of the Sun c 150 000White dwarf 1 109 1 Atomic nuclei 2 3 1017 36 Does not depend strongly on size of nucleusNeutron star core 8 4 1016 1 1018Small black hole 2 1030 37 Critical density of an Earth mass black hole Such densities are possible because white dwarf material is not composed of atoms joined by chemical bonds but rather consists of a plasma of unbound nuclei and electrons There is therefore no obstacle to placing nuclei closer than normally allowed by electron orbitals limited by normal matter 22 Eddington wondered what would happen when this plasma cooled and the energy to keep the atoms ionized was no longer sufficient 38 This paradox was resolved by R H Fowler in 1926 by an application of the newly devised quantum mechanics Since electrons obey the Pauli exclusion principle no two electrons can occupy the same state and they must obey Fermi Dirac statistics also introduced in 1926 to determine the statistical distribution of particles which satisfy the Pauli exclusion principle 39 At zero temperature therefore electrons can not all occupy the lowest energy or ground state some of them would have to occupy higher energy states forming a band of lowest available energy states the Fermi sea This state of the electrons called degenerate meant that a white dwarf could cool to zero temperature and still possess high energy 38 40 Compression of a white dwarf will increase the number of electrons in a given volume Applying the Pauli exclusion principle this will increase the kinetic energy of the electrons thereby increasing the pressure 38 41 This electron degeneracy pressure supports a white dwarf against gravitational collapse The pressure depends only on density and not on temperature Degenerate matter is relatively compressible this means that the density of a high mass white dwarf is much greater than that of a low mass white dwarf and that the radius of a white dwarf decreases as its mass increases 1 The existence of a limiting mass that no white dwarf can exceed without collapsing to a neutron star is another consequence of being supported by electron degeneracy pressure Such limiting masses were calculated for cases of an idealized constant density star in 1929 by Wilhelm Anderson 42 and in 1930 by Edmund C Stoner 43 This value was corrected by considering hydrostatic equilibrium for the density profile and the presently known value of the limit was first published in 1931 by Subrahmanyan Chandrasekhar in his paper The Maximum Mass of Ideal White Dwarfs 44 For a non rotating white dwarf it is equal to approximately 5 7M me2 where me is the average molecular weight per electron of the star 45 eqn 63 As the carbon 12 and oxygen 16 which predominantly compose a carbon oxygen white dwarf both have atomic numbers equal to half their atomic weight one should take me equal to 2 for such a star 40 leading to the commonly quoted value of 1 4 M Near the beginning of the 20th century there was reason to believe that stars were composed chiefly of heavy elements 43 955 so in his 1931 paper Chandrasekhar set the average molecular weight per electron me equal to 2 5 giving a limit of 0 91 M Together with William Alfred Fowler Chandrasekhar received the Nobel Prize for this and other work in 1983 46 The limiting mass is now called the Chandrasekhar limit If a white dwarf were to exceed the Chandrasekhar limit and nuclear reactions did not take place the pressure exerted by electrons would no longer be able to balance the force of gravity and it would collapse into a denser object called a neutron star 47 Carbon oxygen white dwarfs accreting mass from a neighboring star undergo a runaway nuclear fusion reaction which leads to a Type Ia supernova explosion in which the white dwarf may be destroyed before it reaches the limiting mass 48 New research indicates that many white dwarfs at least in certain types of galaxies may not approach that limit by way of accretion It has been postulated that at least some of the white dwarfs that become supernovae attain the necessary mass by colliding with one another It may be that in elliptical galaxies such collisions are the major source of supernovae This hypothesis is based on the fact that the X rays produced by those galaxies are 30 to 50 times less than what is expected to be produced by type Ia supernovas of that galaxy as matter accretes on the white dwarf from its encircling companion It has been concluded that no more than 5 percent of the supernovae in such galaxies could be created by the process of accretion onto white dwarfs The significance of this finding is that there could be two types of supernovae which could mean that the Chandrasekhar limit might not always apply in determining when a white dwarf goes supernova given that two colliding white dwarfs could have a range of masses This in turn would confuse efforts to use exploding white dwarfs as standard candles in determining distances 49 White dwarfs have low luminosity and therefore occupy a strip at the bottom of the Hertzsprung Russell diagram a graph of stellar luminosity versus color or temperature They should not be confused with low luminosity objects at the low mass end of the main sequence such as the hydrogen fusing red dwarfs whose cores are supported in part by thermal pressure 50 or the even lower temperature brown dwarfs 51 Mass radius relationship Edit The relationship between the mass and radius of low mass white dwarfs can be estimated using the nonrelativistic Fermi gas equation of state which gives 40 R N 5 3 ℏ 2 2 m e G M 1 3 displaystyle R approx frac N 5 3 hbar 2 2m e GM 1 3 where R is the radius M is the total mass of the star N is the number of electrons per unit mass dependent only on composition me is the electron mass ℏ displaystyle hbar is the reduced Planck constant and G is the gravitational constant Since this analysis uses the non relativistic formula T p2 2m for the kinetic energy it is non relativistic When the electron velocity in a white dwarf is close to the speed of light the kinetic energy formula approaches T pc where c is the speed of light and it can be shown that there is no stable equilibrium in the ultrarelativistic limit In particular this analysis yields the maximum mass of a white dwarf which is 40 M l i m i t N 2 ℏ c G 3 2 displaystyle M rm limit approx N 2 left frac hbar c G right 3 2 Radius mass relations for a model white dwarf Mlimit is denoted as MCh For a more accurate computation of the mass radius relationship and limiting mass of a white dwarf one must compute the equation of state which describes the relationship between density and pressure in the white dwarf material If the density and pressure are both set equal to functions of the radius from the center of the star the system of equations consisting of the hydrostatic equation together with the equation of state can then be solved to find the structure of the white dwarf at equilibrium In the non relativistic case we will still find that the radius is inversely proportional to the cube root of the mass 45 eqn 80 Relativistic corrections will alter the result so that the radius becomes zero at a finite value of the mass This is the limiting value of the mass called the Chandrasekhar limit at which the white dwarf can no longer be supported by electron degeneracy pressure The graph on the right shows the result of such a computation It shows how radius varies with mass for non relativistic blue curve and relativistic green curve models of a white dwarf Both models treat the white dwarf as a cold Fermi gas in hydrostatic equilibrium The average molecular weight per electron me has been set equal to 2 Radius is measured in standard solar radii and mass in standard solar masses 45 52 These computations all assume that the white dwarf is non rotating If the white dwarf is rotating the equation of hydrostatic equilibrium must be modified to take into account the centrifugal pseudo force arising from working in a rotating frame 53 For a uniformly rotating white dwarf the limiting mass increases only slightly If the star is allowed to rotate nonuniformly and viscosity is neglected then as was pointed out by Fred Hoyle in 1947 54 there is no limit to the mass for which it is possible for a model white dwarf to be in static equilibrium Not all of these model stars will be dynamically stable 55 Rotating white dwarfs and the estimates of their diameter in terms of the angular velocity of rotation has been treated in the rigorous mathematical literature 56 The fine structure of the free boundary of white dwarfs has also been analysed mathematically rigorously 57 Radiation and cooling Edit The degenerate matter that makes up the bulk of a white dwarf has a very low opacity because any absorption of a photon requires that an electron must transition to a higher empty state which may not be possible as the energy of the photon may not be a match for the possible quantum states available to that electron hence radiative heat transfer within a white dwarf is low it does however have a high thermal conductivity As a result the interior of the white dwarf maintains a uniform temperature approximately 107 K An outer shell of non degenerate matter cools from approximately 107 K to 104 K This matter radiates roughly as a black body A white dwarf remains visible for a long time as its tenuous outer atmosphere of normal matter begins to radiate at about 107 K upon formation while its greater interior mass is at 107 K but cannot radiate through its normal matter shell 58 The visible radiation emitted by white dwarfs varies over a wide color range from the whitish blue color of an O B or A type main sequence star to the yellow orange of a late K or early M type star 59 White dwarf effective surface temperatures extend from over 150 000 K 24 to barely under 4 000 K 60 61 In accordance with the Stefan Boltzmann law luminosity increases with increasing surface temperature proportional to T this surface temperature range corresponds to a luminosity from over 100 times the Sun s to under 1 10 000 that of the Sun s 61 Hot white dwarfs with surface temperatures in excess of 30 000 K have been observed to be sources of soft i e lower energy X rays This enables the composition and structure of their atmospheres to be studied by soft X ray and extreme ultraviolet observations 62 White dwarfs also radiate neutrinos through the Urca process 63 This process has more effect on hotter and younger white dwarfs A comparison between the white dwarf IK Pegasi B center its A class companion IK Pegasi A left and the Sun right This white dwarf has a surface temperature of 35 500 K As was explained by Leon Mestel in 1952 unless the white dwarf accretes matter from a companion star or other source its radiation comes from its stored heat which is not replenished 64 65 2 1 White dwarfs have an extremely small surface area to radiate this heat from so they cool gradually remaining hot for a long time 5 As a white dwarf cools its surface temperature decreases the radiation which it emits reddens and its luminosity decreases Since the white dwarf has no energy sink other than radiation it follows that its cooling slows with time The rate of cooling has been estimated for a carbon white dwarf of 0 59 M with a hydrogen atmosphere After initially taking approximately 1 5 billion years to cool to a surface temperature of 7 140 K cooling approximately 500 more kelvins to 6 590 K takes around 0 3 billion years but the next two steps of around 500 kelvins to 6 030 K and 5 550 K take first 0 4 and then 1 1 billion years 66 Table 2 Most observed white dwarfs have relatively high surface temperatures between 8 000 K and 40 000 K 25 67 A white dwarf though spends more of its lifetime at cooler temperatures than at hotter temperatures so we should expect that there are more cool white dwarfs than hot white dwarfs Once we adjust for the selection effect that hotter more luminous white dwarfs are easier to observe we do find that decreasing the temperature range examined results in finding more white dwarfs 68 This trend stops when we reach extremely cool white dwarfs few white dwarfs are observed with surface temperatures below 4 000 K 69 and one of the coolest so far observed WD 0346 246 has a surface temperature of approximately 3 800 K 60 70 The reason for this is that the Universe s age is finite 71 72 there has not been enough time for white dwarfs to cool below this temperature The white dwarf luminosity function can therefore be used to find the time when stars started to form in a region an estimate for the age of our Galactic disk found in this way is 8 billion years 68 A white dwarf will eventually in many trillions of years cool and become a non radiating black dwarf in approximate thermal equilibrium with its surroundings and with the cosmic background radiation No black dwarfs are thought to exist yet 1 The white dwarf cooling sequence seen by ESA s Gaia mission Although white dwarf material is initially plasma a fluid composed of nuclei and electrons it was theoretically predicted in the 1960s that at a late stage of cooling it should crystallize starting at its center 73 The crystal structure is thought to be a body centered cubic lattice 4 74 In 1995 it was suggested that asteroseismological observations of pulsating white dwarfs yielded a potential test of the crystallization theory 75 and in 2004 observations were made that suggested approximately 90 of the mass of BPM 37093 had crystallized 73 76 77 Other work gives a crystallized mass fraction of between 32 and 82 78 As a white dwarf core undergoes crystallization into a solid phase latent heat is released which provides a source of thermal energy that delays its cooling 79 This effect was first confirmed in 2019 after the identification of a pile up in the cooling sequence of more than 15 000 white dwarfs observed with the Gaia satellite 80 Low mass helium white dwarfs mass lt 0 20 M often referred to as extremely low mass white dwarfs ELM WDs are formed in binary systems As a result of their hydrogen rich envelopes residual hydrogen burning via the CNO cycle may keep these white dwarfs hot on a long timescale In addition they remain in a bloated proto white dwarf stage for up to 2 Gyr before they reach the cooling track 81 Atmosphere and spectra Edit Artist s impression of the WD J0914 1914 system 82 Although most white dwarfs are thought to be composed of carbon and oxygen spectroscopy typically shows that their emitted light comes from an atmosphere which is observed to be either hydrogen or helium dominated The dominant element is usually at least 1 000 times more abundant than all other elements As explained by Schatzman in the 1940s the high surface gravity is thought to cause this purity by gravitationally separating the atmosphere so that heavy elements are below and the lighter above 83 84 5 6 This atmosphere the only part of the white dwarf visible to us is thought to be the top of an envelope which is a residue of the star s envelope in the AGB phase and may also contain material accreted from the interstellar medium The envelope is believed to consist of a helium rich layer with mass no more than 1 100 of the star s total mass which if the atmosphere is hydrogen dominated is overlain by a hydrogen rich layer with mass approximately 1 10 000 of the stars total mass 61 85 4 5 Although thin these outer layers determine the thermal evolution of the white dwarf The degenerate electrons in the bulk of a white dwarf conduct heat well Most of a white dwarf s mass is therefore at almost the same temperature isothermal and it is also hot a white dwarf with surface temperature between 8 000 K and 16 000 K will have a core temperature between approximately 5 000 000 K and 20 000 000 K The white dwarf is kept from cooling very quickly only by its outer layers opacity to radiation 61 White dwarf spectral types 24 Primary and secondary featuresA H lines presentB He I linesC Continuous spectrum no linesO He II lines accompanied by He I or H linesZ Metal linesQ Carbon lines presentX Unclear or unclassifiable spectrumSecondary features onlyP Magnetic white dwarf with detectable polarizationH Magnetic white dwarf without detectable polarizationE Emission lines presentV VariableThe first attempt to classify white dwarf spectra appears to have been by G P Kuiper in 1941 59 86 and various classification schemes have been proposed and used since then 87 88 The system currently in use was introduced by Edward M Sion Jesse L Greenstein and their coauthors in 1983 and has been subsequently revised several times It classifies a spectrum by a symbol which consists of an initial D a letter describing the primary feature of the spectrum followed by an optional sequence of letters describing secondary features of the spectrum as shown in the adjacent table and a temperature index number computed by dividing 50 400 K by the effective temperature For example A white dwarf with only He I lines in its spectrum and an effective temperature of 15 000 K could be given the classification of DB3 or if warranted by the precision of the temperature measurement DB3 5 A white dwarf with a polarized magnetic field an effective temperature of 17 000 K and a spectrum dominated by He I lines which also had hydrogen features could be given the classification of DBAP3 The symbols and may also be used if the correct classification is uncertain 24 59 White dwarfs whose primary spectral classification is DA have hydrogen dominated atmospheres They make up the majority approximately 80 of all observed white dwarfs 61 The next class in number is of DBs approximately 16 89 The hot above 15 000 K DQ class roughly 0 1 have carbon dominated atmospheres 90 Those classified as DB DC DO DZ and cool DQ have helium dominated atmospheres Assuming that carbon and metals are not present which spectral classification is seen depends on the effective temperature Between approximately 100 000 K to 45 000 K the spectrum will be classified DO dominated by singly ionized helium From 30 000 K to 12 000 K the spectrum will be DB showing neutral helium lines and below about 12 000 K the spectrum will be featureless and classified DC 85 2 4 61 Molecular hydrogen H2 has been detected in spectra of the atmospheres of some white dwarfs 91 Metal rich white dwarfs Edit Around 25 33 of white dwarfs have metal lines in their spectra which is notable because any heavy elements in a white dwarf should sink into the star s interior in just a small fraction of the star s lifetime 92 The prevailing explanation for metal rich white dwarfs is that they have recently accreted rocky planetesimals 92 The bulk composition of the accreted object can be measured from the strengths of the metal lines For example a 2015 study of the white dwarf Ton 345 concluded that its metal abundances were consistent with those of a differentiated rocky planet whose mantle had been eroded by the host star s wind during its asymptotic giant branch phase 93 Magnetic field Edit Magnetic fields in white dwarfs with a strength at the surface of c 1 million gauss 100 teslas were predicted by P M S Blackett in 1947 as a consequence of a physical law he had proposed which stated that an uncharged rotating body should generate a magnetic field proportional to its angular momentum 94 This putative law sometimes called the Blackett effect was never generally accepted and by the 1950s even Blackett felt it had been refuted 95 39 43 In the 1960s it was proposed that white dwarfs might have magnetic fields due to conservation of total surface magnetic flux that existed in its progenitor star phase 96 A surface magnetic field of c 100 gauss 0 01 T in the progenitor star would thus become a surface magnetic field of c 100 1002 1 million gauss 100 T once the star s radius had shrunk by a factor of 100 84 8 97 484 The first magnetic white dwarf to be discovered was GJ 742 also known as GRW 70 8247 which was identified by James Kemp John Swedlund John Landstreet and Roger Angel in 1970 to host a magnetic field by its emission of circularly polarized light 98 It is thought to have a surface field of approximately 300 million gauss 30 kT 84 8 Since 1970 magnetic fields have been discovered in well over 200 white dwarfs ranging from 2 103 to 109 gauss 0 2 T to 100 kT 99 The large number of presently known magnetic white dwarfs is due to the fact that most white dwarfs are identified by low resolution spectroscopy which is able to reveal the presence of a magnetic field of 1 megagauss or more Thus the basic identification process also sometimes results in discovery of magnetic fields 100 It has been estimated that at least 10 of white dwarfs have fields in excess of 1 million gauss 100 T 101 102 The highly magnetized white dwarf in the binary system AR Scorpii was identified in 2016 as the first pulsar in which the compact object is a white dwarf instead of a neutron star 103 Chemical bonds Edit The magnetic fields in a white dwarf may allow for the existence of a new type of chemical bond perpendicular paramagnetic bonding in addition to ionic and covalent bonds resulting in what has been initially described as magnetized matter in research published in 2012 104 Variability EditMain article Pulsating white dwarf See also Cataclysmic variables Types of pulsating white dwarf 105 106 1 1 1 2 DAV GCVS ZZA DA spectral type having only hydrogen absorption lines in its spectrumDBV GCVS ZZB DB spectral type having only helium absorption lines in its spectrumGW Vir GCVS ZZO Atmosphere mostly C He and O may be divided into DOV and PNNV starsEarly calculations suggested that there might be white dwarfs whose luminosity varied with a period of around 10 seconds but searches in the 1960s failed to observe this 84 7 1 1 107 The first variable white dwarf found was HL Tau 76 in 1965 and 1966 and was observed to vary with a period of approximately 12 5 minutes 108 The reason for this period being longer than predicted is that the variability of HL Tau 76 like that of the other pulsating variable white dwarfs known arises from non radial gravity wave pulsations 84 7 Known types of pulsating white dwarf include the DAV or ZZ Ceti stars including HL Tau 76 with hydrogen dominated atmospheres and the spectral type DA 84 891 895 DBV or V777 Her stars with helium dominated atmospheres and the spectral type DB 61 3525 and GW Vir stars sometimes subdivided into DOV and PNNV stars with atmospheres dominated by helium carbon and oxygen 106 109 GW Vir stars are not strictly speaking white dwarfs but are stars which are in a position on the Hertzsprung Russell diagram between the asymptotic giant branch and the white dwarf region They may be called pre white dwarfs 106 110 These variables all exhibit small 1 30 variations in light output arising from a superposition of vibrational modes with periods of hundreds to thousands of seconds Observation of these variations gives asteroseismological evidence about the interiors of white dwarfs 111 Formation EditWhite dwarfs are thought to represent the end point of stellar evolution for main sequence stars with masses from about 0 07 to 10 M 4 112 The composition of the white dwarf produced will depend on the initial mass of the star Current galactic models suggest the Milky Way galaxy currently contains about ten billion white dwarfs 113 Stars with very low mass Edit If the mass of a main sequence star is lower than approximately half a solar mass it will never become hot enough to fuse helium in its core It is thought that over a lifespan that considerably exceeds the age of the universe c 13 8 billion years 9 such a star will eventually burn all its hydrogen for a while becoming a blue dwarf and end its evolution as a helium white dwarf composed chiefly of helium 4 nuclei 114 Due to the very long time this process takes it is not thought to be the origin of the observed helium white dwarfs Rather they are thought to be the product of mass loss in binary systems 5 7 8 115 116 117 or mass loss due to a large planetary companion 118 119 Stars with low to medium mass Edit If the mass of a main sequence star is between 0 5 and 8 M like our sun its core will become sufficiently hot to fuse helium into carbon and oxygen via the triple alpha process but it will never become sufficiently hot to fuse carbon into neon Near the end of the period in which it undergoes fusion reactions such a star will have a carbon oxygen core which does not undergo fusion reactions surrounded by an inner helium burning shell and an outer hydrogen burning shell On the Hertzsprung Russell diagram it will be found on the asymptotic giant branch It will then expel most of its outer material creating a planetary nebula until only the carbon oxygen core is left This process is responsible for the carbon oxygen white dwarfs which form the vast majority of observed white dwarfs 115 120 121 Stars with medium to high mass Edit If a star is massive enough its core will eventually become sufficiently hot to fuse carbon to neon and then to fuse neon to iron Such a star will not become a white dwarf because the mass of its central non fusing core initially supported by electron degeneracy pressure will eventually exceed the largest possible mass supportable by degeneracy pressure At this point the core of the star will collapse and it will explode in a core collapse supernova which will leave behind a remnant neutron star black hole or possibly a more exotic form of compact star 112 122 Some main sequence stars of perhaps 8 to 10 M although sufficiently massive to fuse carbon to neon and magnesium may be insufficiently massive to fuse neon Such a star may leave a remnant white dwarf composed chiefly of oxygen neon and magnesium provided that its core does not collapse and provided that fusion does not proceed so violently as to blow apart the star in a supernova 123 124 Although a few white dwarfs have been identified which may be of this type most evidence for the existence of such comes from the novae called ONeMg or neon novae The spectra of these novae exhibit abundances of neon magnesium and other intermediate mass elements which appear to be only explicable by the accretion of material onto an oxygen neon magnesium white dwarf 6 125 126 Type Iax supernova Edit Type Iax supernovae that involve helium accretion by a white dwarf have been proposed to be a channel for transformation of this type of stellar remnant In this scenario the carbon detonation produced in a Type Ia supernova is too weak to destroy the white dwarf expelling just a small part of its mass as ejecta but produces an asymmetric explosion that kicks the star often known as a zombie star to high speeds of a hypervelocity star The matter processed in the failed detonation is re accreted by the white dwarf with the heaviest elements such as iron falling to its core where it accumulates 127 These iron core white dwarfs would be smaller than the carbon oxygen kind of similar mass and would cool and crystallize faster than those 128 Fate Edit source source source source source source Artist s concept of white dwarf aging Internal structures of white dwarfs To the left is a newly formed white dwarf in the center is a cooling and crystallizing white dwarf and the right is a black dwarf A white dwarf is stable once formed and will continue to cool almost indefinitely eventually to become a black dwarf Assuming that the universe continues to expand it is thought that in 1019 to 1020 years the galaxies will evaporate as their stars escape into intergalactic space 129 IIIA White dwarfs should generally survive galactic dispersion although an occasional collision between white dwarfs may produce a new fusing star or a super Chandrasekhar mass white dwarf which will explode in a Type Ia supernova 129 IIIC IV The subsequent lifetime of white dwarfs is thought to be on the order of the hypothetical lifetime of the proton known to be at least 1034 1035 years Some grand unified theories predict a proton lifetime between 1030 and 1036 years If these theories are not valid the proton might still decay by complicated nuclear reactions or through quantum gravitational processes involving virtual black holes in these cases the lifetime is estimated to be no more than 10200 years If protons do decay the mass of a white dwarf will decrease very slowly with time as its nuclei decay until it loses enough mass to become a nondegenerate lump of matter and finally disappears completely 129 IV A white dwarf can also be cannibalized or evaporated by a companion star causing the white dwarf to lose so much mass that it becomes a planetary mass object The resultant object orbiting the former companion now host star could be a helium planet or diamond planet 130 131 Debris disks and planets Edit Artist s impression of debris around a white dwarf 132 Comet falling into white dwarf artist s impression 133 A white dwarf s stellar and planetary system is inherited from its progenitor star and may interact with the white dwarf in various ways There are several indications that a white dwarf has a remnant planetary system The most common observable evidence of a remnant planetary system is pollution of the spectrum of a white dwarf with metal absorption lines 27 50 of white dwarfs show a spectrum polluted with metals 134 but these heavy elements settle out in the atmosphere of white dwarfs colder than 20 000 K The most widely accepted hypothesis is that this pollution comes from tidally disrupted rocky bodies 135 136 The first observation of a metal polluted white dwarf was by van Maanen 137 in 1917 at the Mount Wilson Observatory and is now recognized as the first evidence of exoplanets in astronomy 138 The white dwarf van Maanen 2 shows iron calcium and magnesium in its atmosphere 139 but van Maanen misclassified it as the faintest F type star based on the calcium H and K lines 140 The following heavy elements were discovered in the atmosphere of white dwarfs Ca Mg Fe Na Si Cr C O Al Sc Ti V Mn Co Ni Cu Sr S P N Li K Be The nitrogen in white dwarfs is thought to come from nitrogen ice of extrasolar Kuiper Belt objects the lithium is thought to come from accreted crust material and the beryllium is thought to come from exomoons 138 A less common observable evidence is infrared excess due to a flat and optically thick debris disk which is found in around 1 4 of white dwarfs 136 The first white dwarf with infrared excess was discovered by Zuckerman amp Becklin in 1987 in the near infrared around Giclas 29 38 141 and later confirmed as a debris disk 142 White dwarfs hotter than 27 000 K sublimate all the dust formed by tidally disrupting a rocky body preventing the formation of a debris disk In colder white dwarfs a rocky body might be tidally disrupted near the Roche radius and forced into a circular orbit by the Poynting Robertson drag which is stronger for less massive white dwarfs The Poynting Robertson drag will also cause the dust to orbit closer and closer towards the white dwarf until it will eventually sublimate and the disk will disappear A debris disk will have a lifetime of around a few million years for white dwarfs hotter than 10 000 K Colder white dwarfs can have disk lifetimes of a few 10 million years which is enough time to tidally disrupt a second rocky body and forming a second disk around a white dwarf such as the two rings around LSPM J0207 3331 143 The least common observable evidence of planetary systems are detected major or minor planets Only a handful giant planets and a handful of minor planets are known around white dwarfs 144 It is a growing list with discoveries of around 6 exoplanets expected with Gaia 145 and 4 exoplanets with JWST 146 Exoplanet orbits WD 1856 534 source source source source source source source source source source source source source source NASA video 2 10 Infrared spectroscopic observations made by NASA s Spitzer Space Telescope of the central star of the Helix Nebula suggest the presence of a dust cloud which may be caused by cometary collisions It is possible that infalling material from this may cause X ray emission from the central star 147 148 Similarly observations made in 2004 indicated the presence of a dust cloud around the young estimated to have formed from its AGB progenitor about 500 million years ago white dwarf G29 38 which may have been created by tidal disruption of a comet passing close to the white dwarf 142 Some estimations based on the metal content of the atmospheres of the white dwarfs consider that at least 15 of them may be orbited by planets or asteroids or at least their debris 149 Another suggested idea is that white dwarfs could be orbited by the stripped cores of rocky planets that would have survived the red giant phase of their star but losing their outer layers and given those planetary remnants would likely be made of metals to attempt to detect them looking for the signatures of their interaction with the white dwarf s magnetic field 150 Other suggested ideas of how white dwarfs are polluted with dust involve the scattering of asteroids by planets 151 152 153 or via planet planet scattering 154 Liberation of exomoons from their host planet could cause white dwarf pollution with dust Either the liberation could cause asteroids to be scattered towards the white dwarf or the exomoon could be scattered into the Roche radius of the white dwarf 155 The mechanism behind the pollution of white dwarfs in binaries was also explored as these systems are more likely to lack a major planet but this idea cannot explain the presence of dust around single white dwarfs 156 While old white dwarfs show evidence of dust accretion white dwarfs older than 1 billion years or gt 7000 K with dusty infrared excess were not detected 157 until the discovery of LSPM J0207 3331 in 2018 which has a cooling age of 3 billion years The white dwarf shows two dusty components that are being explained with two rings with different temperatures 136 Planets around white dwarfs System name host star minor planet Number of planets Mass planet MJ semi major axis au or R discovery method discovery year Note ReferencePSR B1620 26 white dwarf pulsar 1 2 5 1 23 au pulsar timing 1993 158 NN Serpentis PCEB white dwarf red dwarf 2 c 6 91 0 54 d 2 28 0 38 c 5 38 0 20 au d 3 39 0 10 au eclipse timing variation 2010 PCEB is surrounded by a dusty disk 159 160 WD 0806 661 single 1 1 5 8 2500 au direct imaging 2011 WD 0806 661 B can be interpreted as either a sub brown dwarf or an exoplanet 161 162 WD J0914 1914 single 1 15 16 R detection of accreted planet material viaspectroscopy 2019 likely ice giant 163 WD 1856 534 single 1 gt 0 84 164 4 R transiting 2020 the white dwarf co moves with G 229 20 A B 165 166 167 WD 1145 017 single minor planet 1 1 16 R 168 transiting 2015 169 SDSS J1228 1040 single minor planet 1 0 73 R variable Calcium absorption line 2019 orbits within the debris disk of the white dwarf 170 WD 0145 234 single minor planet 1 1 2 R 171 tidal disruption event 2019 172 ZTF J0139 5245 single minor planet 1 0 36 au transiting 2020 highly eccentric orbit e gt 0 97 144 173 174 ZTF J0328 1219 single minor planet 2 b 2 11 R c 2 28 R transiting 2021 discovery paper also describes candidates around 4 other white dwarfs 175 176 The metal rich white dwarf WD 1145 017 is the first white dwarf observed with a disintegrating minor planet which transits the star 177 169 The disintegration of the planetesimal generates a debris cloud which passes in front of the star every 4 5 hours causing a 5 minute long fade in the star s optical brightness 169 The depth of the transit is highly variable 169 The giant planet WD J0914 1914b is being evaporated by the strong ultraviolet radiation of the hot white dwarf Part of the evaporated material is being accreted in a gaseous disk around the white dwarf The weak hydrogen line as well as other lines in the spectrum of the white dwarf revealed the presence of the giant planet 163 The white dwarf WD 0145 234 shows brightening in the mid infrared seen in NEOWISE data The brightening is not seen before 2018 It is interpreted as the tidal disruption of an exoasteroid the first time such an event has been observed 172 WD 1856 534 is the first and only transiting major planet around a white dwarf as of 2022 Habitability EditIt has been proposed that white dwarfs with surface temperatures of less than 10 000 Kelvins could harbor a habitable zone at a distance of c 0 005 to 0 02 AU that would last upwards of 3 billion years This is so close that any habitable planets would be tidally locked The goal is to search for transits of hypothetical Earth like planets that could have migrated inward or formed there As a white dwarf has a size similar to that of a planet these kinds of transits would produce strong eclipses 178 Newer research casts some doubts on this idea given that the close orbits of those hypothetical planets around their parent stars would subject them to strong tidal forces that could render them uninhabitable by triggering a greenhouse effect 179 Another suggested constraint to this idea is the origin of those planets Leaving aside formation from the accretion disk surrounding the white dwarf there are two ways a planet could end in a close orbit around stars of this kind by surviving being engulfed by the star during its red giant phase and then spiralling inward or inward migration after the white dwarf has formed The former case is implausible for low mass bodies as they are unlikely to survive being absorbed by their stars In the latter case the planets would have to expel so much orbital energy as heat through tidal interactions with the white dwarf that they would likely end as uninhabitable embers 180 Binary stars and novae Edit The merger process of two co orbiting white dwarfs produces gravitational waves If a white dwarf is in a binary star system and is accreting matter from its companion a variety of phenomena may occur including novae and Type Ia supernovae It may also be a super soft x ray source if it is able to take material from its companion fast enough to sustain fusion on its surface 181 On the other hand phenomena in binary systems such as tidal interaction and star disc interaction moderated by magnetic fields or not act on the rotation of accreting white dwarfs In fact the securely known fastest spinning white dwarfs are members of binary systems the fastest one being the white dwarf in CTCV J2056 3014 182 A close binary system of two white dwarfs can radiate energy in the form of gravitational waves causing their mutual orbit to steadily shrink until the stars merge 183 184 Type Ia supernovae Edit Main article Type Ia supernova The mass of an isolated nonrotating white dwarf cannot exceed the Chandrasekhar limit of 1 4 M This limit may increase if the white dwarf is rotating rapidly and nonuniformly 185 White dwarfs in binary systems can accrete material from a companion star increasing both their mass and their density As their mass approaches the Chandrasekhar limit this could theoretically lead to either the explosive ignition of fusion in the white dwarf or its collapse into a neutron star 47 Accretion provides the currently favored mechanism called the single degenerate model for Type Ia supernovae In this model a carbon oxygen white dwarf accretes mass and compresses its core by pulling mass from a companion star 48 14 It is believed that compressional heating of the core leads to ignition of carbon fusion as the mass approaches the Chandrasekhar limit 48 Because the white dwarf is supported against gravity by quantum degeneracy pressure instead of by thermal pressure adding heat to the star s interior increases its temperature but not its pressure so the white dwarf does not expand and cool in response Rather the increased temperature accelerates the rate of the fusion reaction in a runaway process that feeds on itself The thermonuclear flame consumes much of the white dwarf in a few seconds causing a Type Ia supernova explosion that obliterates the star 1 48 186 In another possible mechanism for Type Ia supernovae the double degenerate model two carbon oxygen white dwarfs in a binary system merge creating an object with mass greater than the Chandrasekhar limit in which carbon fusion is then ignited 48 14 Observations have failed to note signs of accretion leading up to Type Ia supernovae and this is now thought to be because the star is first loaded up to above the Chandrasekhar limit while also being spun up to a very high rate by the same process Once the accretion stops the star gradually slows until the spin is no longer enough to prevent the explosion 187 The historical bright SN 1006 is thought to have been a type Ia supernova from a white dwarf possibly the merger of two white dwarfs 188 Tycho s Supernova of 1572 was also a type Ia supernova and its remnant has been detected 189 A close candidate to being a survivor of a type Ia supernova is WD 0810 353 190 Post common envelope binary Edit Main article Post common envelope binary A post common envelope binary PCEB is a binary consisting of a white dwarf and a closely tidally locked red dwarf in other cases this might be a brown dwarf instead of a red dwarf These binaries form when the red dwarf is engulfed in the red giant phase As the red dwarf orbits inside the common envelope it is slowed down in the denser environment This slowed orbital speed is compensated with a decrease of the orbital distance between the red dwarf and the core of the red giant The red dwarf spirals inwards towards the core and might merge with the core If this does not happen and instead the common envelope is ejected then the binary ends up in a close orbit consisting of a white dwarf and a red dwarf This type of binary is called a post common envelope binary The evolution of the PCEB continues as the two dwarf stars orbit closer and closer due to magnetic braking and by releasing gravitational waves The binary might evolve at some point into a cataclysmic variable and therefore post common envelope binaries are sometimes called pre cataclysmic variables Cataclysmic variables Edit Main article Cataclysmic variable star Before accretion of material pushes a white dwarf close to the Chandrasekhar limit accreted hydrogen rich material on the surface may ignite in a less destructive type of thermonuclear explosion powered by hydrogen fusion These surface explosions can be repeated as long as the white dwarf s core remains intact This weaker kind of repetitive cataclysmic phenomenon is called a classical nova Astronomers have also observed dwarf novae which have smaller more frequent luminosity peaks than the classical novae These are thought to be caused by the release of gravitational potential energy when part of the accretion disc collapses onto the star rather than through a release of energy due to fusion In general binary systems with a white dwarf accreting matter from a stellar companion are called cataclysmic variables As well as novae and dwarf novae several other classes of these variables are known including polars and intermediate polars both of which feature highly magnetic white dwarfs 1 48 191 192 Both fusion and accretion powered cataclysmic variables have been observed to be X ray sources 192 Other non pre supernova binaries Edit Other non pro supernova binaries include binaries that consist of a main sequence star or giant and a white dwarf The binary Sirius AB is probably the most famous example White dwarfs can also exist as binaries or multiple star systems that only consist of white dwarfs An example of a resolved triple white dwarf system is WD J1953 1019 discovered with Gaia DR2 data One interesting field is the study of remnant planetary systems around white dwarfs While stars are bright and often outshine the exoplanets and brown dwarfs that orbit them the white dwarfs are faint This allows astronomers to study these brown dwarfs or exoplanets in more detail The sub brown dwarf around the white dwarf WD 0806 661 is one such example Nearest EditWhite Dwarfs within 25 Light Years 193 Identifier WD Number Distance ly Type Absolutemagnitude Mass M Luminosity L Age Gyr Objects in systemSirius B 0642 166 8 66 DA 11 18 0 98 0 0295 0 10 2Procyon B 0736 053 11 46 DQZ 13 20 0 63 0 00049 1 37 2Van Maanen 2 0046 051 14 07 DZ 14 09 0 68 0 00017 3 30 1LP 145 141 1142 645 15 12 DQ 12 77 0 61 0 00054 1 29 140 Eridani B 0413 077 16 39 DA 11 27 0 59 0 0141 0 12 3Stein 2051 B 0426 588 17 99 DC 13 43 0 69 0 00030 2 02 2G 240 72 1748 708 20 26 DQ 15 23 0 81 0 000085 5 69 1Gliese 223 2 0552 041 21 01 DZ 15 29 0 82 0 000062 7 89 1Gliese 3991 B 194 1708 437 24 23 D gt 15 0 5 lt 0 000086 gt 6 2Gallery Edit Illustration of rocky debris around a white dwarf 195 Cocoon of a new white dwarf in the centre of NGC 2440 Artist s impression of an evolving white dwarf and millisecond pulsar binary system 196 Illustration of an ultracool dwarf with a companion white dwarf 197 See also EditBlack dwarf Theoretical stellar remnant Brown dwarf Type of substellar object larger than a planet Chandrasekhar s white dwarf equation Degenerate matter Physics a type of dense exotic matter List of white dwarfs Neutron star Collapsed core of a massive star PG 1159 star Planetary nebula Type of emission nebula Robust associations of massive baryonic objects Proposed type of star cluster Stellar classification Classification of stars based on their spectral characteristics Timeline of white dwarfs neutron stars and supernovae Chronological list of developments in knowledge and recordsReferences Edit a b c d e f g h i Johnson J 2007 Extreme stars White dwarfs amp neutron stars Lecture notes Astronomy 162 Ohio State University Archived from the original on 31 March 2012 Retrieved 17 October 2011 Henry T J 1 January 2009 The one hundred nearest star systems Research Consortium on Nearby Stars Archived from the original on 12 November 2007 Retrieved 21 July 2010 a b c d Evry L Schatzman 1958 White Dwarfs North Holland Publishing Company ISBN 978 0 598 58212 6 a b c d Fontaine G Brassard P Bergeron P 2001 The potential of white dwarf cosmochronology Publications of the Astronomical Society of the Pacific 113 782 409 435 Bibcode 2001PASP 113 409F doi 10 1086 319535 a b c d e Richmond M Late stages of evolution for low mass stars Lecture notes Physics 230 Rochester Institute of Technology Archived from the original on 4 September 2017 Retrieved 3 May 2007 a b Werner K Hammer N J Nagel T Rauch T Dreizler S 2005 On possible oxygen neon white dwarfs H1504 65 and the white dwarf donors in ultracompact X ray binaries 14th European Workshop on White Dwarfs Vol 334 p 165 arXiv astro ph 0410690 Bibcode 2005ASPC 334 165W a b Liebert James Bergeron P Eisenstein D Harris H C Kleinman S J Nitta A Krzesinski J 2004 A helium white dwarf of extremely low mass The Astrophysical Journal 606 2 L147 arXiv astro ph 0404291 Bibcode 2004ApJ 606L 147L doi 10 1086 421462 S2CID 118894713 a b Cosmic weight loss The lowest mass white dwarf Press release Harvard Smithsonian Center for Astrophysics 17 April 2007 Archived from the original on 22 April 2007 Retrieved 20 April 2007 a b Spergel D N Bean R Dore O Nolta M R Bennett C L Dunkley J et al 2007 Wilkinson Microwave Anisotropy Probe WMAP three year results Implications for cosmology The Astrophysical Journal Supplement Series 170 2 377 408 arXiv astro ph 0603449 Bibcode 2007ApJS 170 377S doi 10 1086 513700 S2CID 1386346 3 Heger A Fryer C L Woosley S E Langer N Hartmann D H 2003 How massive single stars end their life Astrophysical Journal 591 1 288 300 arXiv astro ph 0212469 Bibcode 2003ApJ 591 288H doi 10 1086 375341 S2CID 59065632 Herschel W 1785 Catalogue of Double Stars Philosophical Transactions of the Royal Society of London 75 40 126 Bibcode 1785RSPT 75 40H doi 10 1098 rstl 1785 0006 JSTOR 106749 S2CID 186209747 a b c Holberg J B 2005 How degenerate stars came to be known as white dwarfs American Astronomical Society meeting 207 Vol 207 p 1503 Bibcode 2005AAS 20720501H Adams W S 1914 An A type star of very low luminosity Publications of the Astronomical Society of the Pacific 26 155 198 Bibcode 1914PASP 26 198A doi 10 1086 122337 a b Bessel F W 1844 On the variations of the proper motions of Procyon and Sirius Monthly Notices of the Royal Astronomical Society 6 11 136 141 Bibcode 1844MNRAS 6R 136B doi 10 1093 mnras 6 11 136a a b Flammarion Camille 1877 The companion of Sirius Astronomical Register 15 186 Bibcode 1877AReg 15 186F Adams W S 1915 The spectrum of the companion of Sirius Publications of the Astronomical Society of the Pacific 27 161 236 Bibcode 1915PASP 27 236A doi 10 1086 122440 van Maanen A 1917 Two faint stars with large proper motion Publications of the Astronomical Society of the Pacific 29 172 258 Bibcode 1917PASP 29 258V doi 10 1086 122654 Luyten W J 1922 The mean parallax of early type stars of determined proper motion and apparent magnitude Publications of the Astronomical Society of the Pacific 34 199 156 Bibcode 1922PASP 34 156L doi 10 1086 123176 Luyten W J 1922 Note on some faint early type stars with large proper motions Publications of the Astronomical Society of the Pacific 34 197 54 Bibcode 1922PASP 34 54L doi 10 1086 123146 Luyten W J 1922 Additional note on faint early type stars with large proper motions Publications of the Astronomical Society of the Pacific 34 198 132 Bibcode 1922PASP 34 132L doi 10 1086 123168 Aitken R G 1922 Comet c 1922 Baade Publications of the Astronomical Society of the Pacific 34 202 353 Bibcode 1922PASP 34 353A doi 10 1086 123244 a b c Eddington A S 1924 On the relation between the masses and luminosities of the stars Monthly Notices of the Royal Astronomical Society 84 5 308 333 Bibcode 1924MNRAS 84 308E doi 10 1093 mnras 84 5 308 Luyten W J 1950 The search for white dwarfs The Astronomical Journal 55 86 Bibcode 1950AJ 55 86L doi 10 1086 106358 a b c d McCook George P Sion Edward M 1999 A catalog of spectroscopically identified white dwarfs The Astrophysical Journal Supplement Series 121 1 1 130 Bibcode 1999ApJS 121 1M doi 10 1086 313186 a b Eisenstein Daniel J Liebert James Harris Hugh C Kleinman S J Nitta Atsuko Silvestri Nicole et al 2006 A catalog of spectroscopically confirmed white dwarfs from the Sloan Digital Sky Survey data release 4 The Astrophysical Journal Supplement Series 167 1 40 58 arXiv astro ph 0606700 Bibcode 2006ApJS 167 40E doi 10 1086 507110 S2CID 13829139 Kilic M Allende Prieto C Brown Warren R Koester D 2007 The lowest mass white dwarf The Astrophysical Journal 660 2 1451 1461 arXiv astro ph 0611498 Bibcode 2007ApJ 660 1451K doi 10 1086 514327 S2CID 18587748 a b Kepler S O Kleinman S J Nitta A Koester D Castanheira B G Giovannini O Costa A F M Althaus L 2007 White dwarf mass distribution in the SDSS Monthly Notices of the Royal Astronomical Society 375 4 1315 1324 arXiv astro ph 0612277 Bibcode 2007MNRAS 375 1315K doi 10 1111 j 1365 2966 2006 11388 x S2CID 10892288 Shipman H L 1979 Masses and radii of white dwarf stars III Results for 110 hydrogen rich and 28 helium rich stars The Astrophysical Journal 228 240 Bibcode 1979ApJ 228 240S doi 10 1086 156841 Sandin F 2005 Exotic Phases of Matter in Compact Stars PDF Licentiate thesis Lulea University of Technology Archived PDF from the original on 15 August 2011 Retrieved 20 August 2011 Boss L 1910 Preliminary General Catalogue of 6188 stars for the epoch 1900 Carnegie Institution of Washington Bibcode 1910pgcs book B LCCN 10009645 via Archive org Liebert James Young P A Arnett D Holberg J B Williams K A 2005 The age and progenitor mass of Sirius B The Astrophysical Journal 630 1 L69 arXiv astro ph 0507523 Bibcode 2005ApJ 630L 69L doi 10 1086 462419 S2CID 8792889 Opik E 1916 The densities of visual binary stars The Astrophysical Journal 44 292 Bibcode 1916ApJ 44 292O doi 10 1086 142296 Eddington A S 1927 Stars and Atoms Clarendon Press LCCN 27015694 Adams W S 1925 The Relativity Displacement of the Spectral Lines in the Companion of Sirius Proceedings of the National Academy of Sciences 11 7 382 387 Bibcode 1925PNAS 11 382A doi 10 1073 pnas 11 7 382 PMC 1086032 PMID 16587023 Celotti A Miller J C Sciama D W 1999 Astrophysical evidence for the existence of black holes Class Quantum Grav 16 12A A3 A21 arXiv astro ph 9912186 Bibcode 1999CQGra 16A 3C doi 10 1088 0264 9381 16 12A 301 S2CID 17677758 Nave C R Nuclear Size and Density HyperPhysics Georgia State University Archived from the original on 6 July 2009 Retrieved 26 June 2009 Adams Steve 1997 Relativity an introduction to space time physics Relativity An Introduction to Space Time Physics London Bristol CRC Press p 240 Bibcode 1997rist book A ISBN 978 0 7484 0621 0 a b c Fowler R H 1926 On dense matter Monthly Notices of the Royal Astronomical Society 87 2 114 122 Bibcode 1926MNRAS 87 114F doi 10 1093 mnras 87 2 114 Hoddeson L H Baym G 1980 The Development of the Quantum Mechanical Electron Theory of Metals 1900 28 Proceedings of the Royal Society of London 371 1744 8 23 Bibcode 1980RSPSA 371 8H doi 10 1098 rspa 1980 0051 JSTOR 2990270 S2CID 120476662 a b c d Estimating Stellar Parameters from Energy Equipartition ScienceBits Archived from the original on 22 May 2012 Retrieved 9 May 2007 Bean R Lecture 12 Degeneracy pressure PDF Lecture notes Astronomy 211 Cornell University Archived from the original PDF on 25 September 2007 Retrieved 21 September 2007 Anderson W 1929 Uber die Grenzdichte der Materie und der Energie Zeitschrift fur Physik in German 56 11 12 851 856 Bibcode 1929ZPhy 56 851A doi 10 1007 BF01340146 S2CID 122576829 a b Stoner C 1930 The Equilibrium of Dense Stars Philosophical Magazine 9 944 Chandrasekhar S 1931 The Maximum Mass of Ideal White Dwarfs The Astrophysical Journal 74 81 Bibcode 1931ApJ 74 81C doi 10 1086 143324 a b c Chandrasekhar S 1935 The highly collapsed configurations of a stellar mass Second paper Monthly Notices of the Royal Astronomical Society 95 3 207 225 Bibcode 1935MNRAS 95 207C doi 10 1093 mnras 95 3 207 The Nobel Prize in Physics 1983 The Nobel Foundation Archived from the original on 6 May 2007 Retrieved 4 May 2007 a b Canal R Gutierrez J 1997 The Possible White Dwarf Neutron Star Connection White Dwarfs Astrophysics and Space Science Library Vol 214 pp 49 55 arXiv astro ph 9701225 Bibcode 1997ASSL 214 49C doi 10 1007 978 94 011 5542 7 7 ISBN 978 94 010 6334 0 S2CID 9288287 a b c d e f Hillebrandt W Niemeyer J C 2000 Type IA supernova explosion models Annual Review of Astronomy and Astrophysics 38 191 230 arXiv astro ph 0006305 Bibcode 2000ARA amp A 38 191H doi 10 1146 annurev astro 38 1 191 S2CID 10210550 Overbye D 22 February 2010 From the Clash of White Dwarfs the Birth of a Supernova The New York Times Archived from the original on 25 February 2010 Retrieved 22 February 2010 Chabrier G Baraffe I 2000 Theory of low Mass stars and substellar objects Annual Review of Astronomy and Astrophysics 38 337 377 arXiv astro ph 0006383 Bibcode 2000ARA amp A 38 337C doi 10 1146 annurev astro 38 1 337 S2CID 59325115 Kaler J The Hertzsprung Russell HR diagram Archived from the original on 31 August 2009 Retrieved 5 May 2007 Basic symbols Standards for Astronomical Catalogues Version 2 0 VizieR Archived from the original on 8 May 2017 Retrieved 12 January 2007 Tohline J E The Structure Stability and Dynamics of Self Gravitating Systems Archived from the original on 27 June 2010 Retrieved 30 May 2007 Hoyle F 1947 Stars Distribution and Motions of Note on equilibrium configurations for rotating white dwarfs Monthly Notices of the Royal Astronomical Society 107 2 231 236 Bibcode 1947MNRAS 107 231H doi 10 1093 mnras 107 2 231 Ostriker J P Bodenheimer P 1968 Rapidly Rotating Stars II Massive White Dwarfs The Astrophysical Journal 151 1089 Bibcode 1968ApJ 151 1089O doi 10 1086 149507 Chanillo Sagun Li Yan Yan 1994 On diameters of uniformly rotating stars Communications in Mathematical Physics 166 2 417 Bibcode 1994CMaPh 166 417C doi 10 1007 BF02112323 S2CID 8372549 Chanillo Sagun Weiss Georg S 2012 A remark on the geometry of uniformly rotating stars Journal of Differential Equations 253 2 553 arXiv 1109 3046 Bibcode 2012JDE 253 553C doi 10 1016 j jde 2012 04 011 S2CID 144301 Kutner M L 2003 Astronomy A physical perspective Cambridge University Press p 189 ISBN 978 0 521 52927 3 Retrieved 28 February 2016 a b c Sion E M Greenstein J L Landstreet J D Liebert James Shipman H L Wegner G A 1983 A proposed new white dwarf spectral classification system The Astrophysical Journal 269 253 Bibcode 1983ApJ 269 253S doi 10 1086 161036 a b Hambly N C Smartt S J Hodgkin S T 1997 WD 0346 246 A Very Low Luminosity Cool Degenerate in Taurus The Astrophysical Journal 489 2 L157 Bibcode 1997ApJ 489L 157H doi 10 1086 316797 a b c d e f g Fontaine G Wesemael F 2001 White dwarfs In Murdin P ed Encyclopedia of Astronomy and Astrophysics IOP Publishing Nature Publishing Group ISBN 978 0 333 75088 9 Heise J 1985 X ray emission from isolated hot white dwarfs Space Science Reviews 40 1 2 79 90 Bibcode 1985SSRv 40 79H doi 10 1007 BF00212870 S2CID 120431159 Lesaffre P Podsiadlowski Ph Tout C A 2005 A two stream formalism for the convective Urca process Monthly Notices of the Royal Astronomical Society 356 1 131 144 arXiv astro ph 0411016 Bibcode 2005MNRAS 356 131L doi 10 1111 j 1365 2966 2004 08428 x S2CID 15797437 Mestel L 1952 On the theory of white dwarf stars I The energy sources of white dwarfs Monthly Notices of the Royal Astronomical Society 112 6 583 597 Bibcode 1952MNRAS 112 583M doi 10 1093 mnras 112 6 583 Kawaler S D 1998 White Dwarf Stars and the Hubble Deep Field The Hubble Deep Field Proceedings of the Space Telescope Science Institute Symposium p 252 arXiv astro ph 9802217 Bibcode 1998hdf symp 252K ISBN 978 0 521 63097 9 Bergeron P Ruiz M T Leggett S K 1997 The Chemical Evolution of Cool White Dwarfs and the Age of the Local Galactic Disk The Astrophysical Journal Supplement Series 108 1 339 387 Bibcode 1997ApJS 108 339B doi 10 1086 312955 McCook G P Sion E M 1999 A Catalogue of Spectroscopically Identified White Dwarfs The Astrophysical Journal Supplement Series 121 1 1 130 Bibcode 1999ApJS 121 1M doi 10 1086 313186 a b Leggett S K Ruiz M T Bergeron P 1998 The Cool White Dwarf Luminosity Function and the Age of the Galactic Disk The Astrophysical Journal 497 1 294 302 Bibcode 1998ApJ 497 294L doi 10 1086 305463 Gates E Gyuk G Harris H C Subbarao M Anderson S Kleinman S J Liebert James Brewington H et al 2004 Discovery of New Ultracool White Dwarfs in the Sloan Digital Sky Survey The Astrophysical Journal 612 2 L129 arXiv astro ph 0405566 Bibcode 2004ApJ 612L 129G doi 10 1086 424568 S2CID 7570539 Kilic M Thorstensen J R Kowalski P M Andrews J 2012 11 12 Gyr old white dwarfs 30 pc away Monthly Notices of the Royal Astronomical Society Letters 423 1 L132 L136 arXiv 1204 2570 Bibcode 2012MNRAS 423L 132K doi 10 1111 j 1745 3933 2012 01271 x Winget D E Hansen C J Liebert James Van Horn H M Fontaine G Nather R E Kepler S O Lamb D Q 1987 An independent method for determining the age of the universe The Astrophysical Journal 315 L77 Bibcode 1987ApJ 315L 77W doi 10 1086 184864 hdl 10183 108730 Trefil J S 2004 The Moment of Creation Big Bang Physics from Before the First Millisecond to the Present Universe Dover Publications ISBN 978 0 486 43813 9 a b Metcalfe T S Montgomery M H Kanaan A 2004 Testing White Dwarf Crystallization Theory with Asteroseismology of the Massive Pulsating DA Star BPM 37093 The Astrophysical Journal 605 2 L133 arXiv astro ph 0402046 Bibcode 2004ApJ 605L 133M doi 10 1086 420884 S2CID 119378552 Barrat J L Hansen J P Mochkovitch R 1988 Crystallization of carbon oxygen mixtures in white dwarfs Astronomy and Astrophysics 199 1 2 L15 Bibcode 1988A amp A 199L 15B Winget D E 1995 The Status of White Dwarf Asteroseismology and a Glimpse of the Road Ahead Baltic Astronomy 4 2 129 Bibcode 1995BaltA 4 129W doi 10 1515 astro 1995 0209 Whitehouse David 16 February 2004 Diamond star thrills astronomers BBC News Archived from the original on 5 February 2007 Retrieved 6 January 2007 Kanaan A Nitta A Winget D E Kepler S O Montgomery M H Metcalfe T S Oliveira H Fraga L et al 2005 Whole Earth Telescope observations of BPM 37093 A seismological test of crystallization theory in white dwarfs Astronomy and Astrophysics 432 1 219 224 arXiv astro ph 0411199 Bibcode 2005A amp A 432 219K doi 10 1051 0004 6361 20041125 S2CID 7297628 Brassard P Fontaine G 2005 Asteroseismology of the Crystallized ZZ Ceti Star BPM 37093 A Different View The Astrophysical Journal 622 1 572 576 Bibcode 2005ApJ 622 572B doi 10 1086 428116 Hansen B M S Liebert James 2003 Cool White Dwarfs Annual Review of Astronomy and Astrophysics 41 465 Bibcode 2003ARA amp A 41 465H doi 10 1146 annurev astro 41 081401 155117 Tremblay P E Fontaine G Fusillo N P G Dunlap B H Gansicke B T Hollands M H Hermes J J Marsh T R Cukanovaite E Cunningham T 2019 Core crystallization and pile up in the cooling sequence of evolving white dwarfs PDF Nature 565 7738 202 205 arXiv 1908 00370 Bibcode 2019Natur 565 202T doi 10 1038 s41586 018 0791 x PMID 30626942 S2CID 58004893 Archived PDF from the original on 23 July 2019 Retrieved 23 July 2019 Istrate et al 2014 The timescale of low mass proto helium white dwarf evolution Astronomy and Astrophysics 571 L3 arXiv 1410 5471 Bibcode 2014A amp A 571L 3I doi 10 1051 0004 6361 201424681 S2CID 55152203 First Giant Planet around White Dwarf Found ESO observations indicate the Neptune like exoplanet is evaporating www eso org Archived from the original on 4 December 2019 Retrieved 4 December 2019 Schatzman E 1945 Theorie du debit d energie des naines blanches Annales d Astrophysique 8 143 Bibcode 1945AnAp 8 143S a b c d e f Koester D Chanmugam G 1990 Physics of white dwarf stars Reports on Progress in Physics 53 7 837 915 Bibcode 1990RPPh 53 837K doi 10 1088 0034 4885 53 7 001 S2CID 122582479 a b Kawaler S D 1997 White Dwarf Stars In Kawaler S D Novikov I Srinivasan G eds Stellar remnants 1997 ISBN 978 3 540 61520 0 Kuiper G P 1941 List of Known White Dwarfs Publications of the Astronomical Society of the Pacific 53 314 248 Bibcode 1941PASP 53 248K doi 10 1086 125335 Luyten W J 1952 The Spectra and Luminosities of White Dwarfs The Astrophysical Journal 116 283 Bibcode 1952ApJ 116 283L doi 10 1086 145612 Greenstein J L 1960 Stellar atmospheres University of Chicago Press Bibcode 1960stat book G LCCN 61 9138 Kepler S O Kleinman S J Nitta A Koester D Castanheira B G Giovannini O Costa A F M Althaus L 2007 White dwarf mass distribution in the SDSS Monthly Notices of the Royal Astronomical Society 375 4 1315 1324 arXiv astro ph 0612277 Bibcode 2007MNRAS 375 1315K doi 10 1111 j 1365 2966 2006 11388 x S2CID 10892288 Dufour P Liebert James Fontaine G Behara N 2007 White dwarf stars with carbon atmospheres Nature 450 7169 522 4 arXiv 0711 3227 Bibcode 2007Natur 450 522D doi 10 1038 nature06318 PMID 18033290 S2CID 4398697 Xu S Jura M Koester D Klein B Zuckerman B 2013 Discovery of Molecular Hydrogen in White Dwarf Atmospheres The Astrophysical Journal 766 2 L18 arXiv 1302 6619 Bibcode 2013ApJ 766L 18X doi 10 1088 2041 8205 766 2 L18 S2CID 119248244 a b Jura M Young E D 1 January 2014 Extrasolar Cosmochemistry Annual Review of Earth and Planetary Sciences 42 1 45 67 Bibcode 2014AREPS 42 45J doi 10 1146 annurev earth 060313 054740 Wilson D J Gansicke B T Koester D Toloza O Pala A F Breedt E Parsons S G 11 August 2015 The composition of a disrupted extrasolar planetesimal at SDSS J0845 2257 Ton 345 Monthly Notices of the Royal Astronomical Society 451 3 3237 3248 arXiv 1505 07466 Bibcode 2015MNRAS 451 3237W doi 10 1093 mnras stv1201 S2CID 54049842 Blackett P M S 1947 The Magnetic Field of Massive Rotating Bodies Nature 159 4046 658 66 Bibcode 1947Natur 159 658B doi 10 1038 159658a0 PMID 20239729 S2CID 4133416 Lovell B 1975 Patrick Maynard Stuart Blackett Baron Blackett of Chelsea 18 November 1897 13 July 1974 Biographical Memoirs of Fellows of the Royal Society 21 1 115 doi 10 1098 rsbm 1975 0001 JSTOR 769678 S2CID 74674634 Landstreet John D 1967 Synchrotron radiation of neutrinos and its astrophysical significance Physical Review 153 5 1372 1377 Bibcode 1967PhRv 153 1372L doi 10 1103 PhysRev 153 1372 Ginzburg V L Zheleznyakov V V Zaitsev V V 1969 Coherent mechanisms of radio emission and magnetic models of pulsars Astrophysics and Space Science 4 4 464 504 Bibcode 1969Ap amp SS 4 464G doi 10 1007 BF00651351 S2CID 119003761 Kemp J C Swedlund J B Landstreet J D Angel J R P 1970 Discovery of circularly polarized light from a white dwarf The Astrophysical Journal 161 L77 Bibcode 1970ApJ 161L 77K doi 10 1086 180574 Ferrario Lilia de Martino Domtilla Gaensicke Boris 2015 Magnetic white dwarfs Space Science Reviews 191 1 4 111 169 arXiv 1504 08072 Bibcode 2015SSRv 191 111F doi 10 1007 s11214 015 0152 0 S2CID 119057870 Kepler S O Pelisoli I Jordan S Kleinman S J Koester D Kuelebi B Pecanha V Castanhiera B G Nitta A Costa J E S Winget D E Kanaan A Fraga L 2013 Magnetic white dwarf stars in the Sloan Digital Sky Survey Monthly Notices of the Royal Astronomical Society 429 4 2934 2944 arXiv 1211 5709 Bibcode 2013MNRAS 429 2934K doi 10 1093 mnras sts522 S2CID 53316287 Landstreet J D Bagnulo S Valyavin G G Fossati L Jordan S Monin D Wade G A 2012 On the incidence of weak magnetic fields in DA white dwarfs Astronomy and Astrophysics 545 A30 9pp arXiv 1208 3650 Bibcode 2012A amp A 545A 30L doi 10 1051 0004 6361 201219829 S2CID 55153825 Liebert James Bergeron P Holberg J B 2003 The True Incidence of Magnetism Among Field White Dwarfs The Astronomical Journal 125 1 348 353 arXiv astro ph 0210319 Bibcode 2003AJ 125 348L doi 10 1086 345573 S2CID 9005227 Buckley D A H Meintjes P J Potter S B Marsh T R Gansicke B T 23 January 2017 Polarimetric evidence of a white dwarf pulsar in the binary system AR Scorpii Nature Astronomy 1 2 0029 arXiv 1612 03185 Bibcode 2017NatAs 1E 29B doi 10 1038 s41550 016 0029 S2CID 15683792 Merali Zeeya 19 July 2012 Stars draw atoms closer together Nature News amp Comment Nature doi 10 1038 nature 2012 11045 Archived from the original on 20 July 2012 Retrieved 21 July 2012 ZZ Ceti variables Centre deDonnees astronomiques de Strasbourg Association Francaise des Observateurs d Etoiles Variables Archived from the original on 5 February 2007 Retrieved 6 June 2007 a b c Quirion P O Fontaine G Brassard P 2007 Mapping the Instability Domains of GW Vir Stars in the Effective Temperature Surface Gravity Diagram The Astrophysical Journal Supplement Series 171 1 219 248 Bibcode 2007ApJS 171 219Q doi 10 1086 513870 Lawrence G M Ostriker J P Hesser J E 1967 Ultrashort Period Stellar Oscillations I Results from White Dwarfs Old Novae Central Stars of Planetary Nebulae 3c 273 and Scorpius XR 1 The Astrophysical Journal 148 L161 Bibcode 1967ApJ 148L 161L doi 10 1086 180037 Landolt A U 1968 A New Short Period Blue Variable The Astrophysical Journal 153 151 Bibcode 1968ApJ 153 151L doi 10 1086 149645 Nagel T Werner K 2004 Detection of non radial g mode pulsations in the newly discovered PG 1159 star HE 1429 1209 Astronomy and Astrophysics 426 2 L45 arXiv astro ph 0409243 Bibcode 2004A amp A 426L 45N doi 10 1051 0004 6361 200400079 S2CID 9481357 O Brien M S 2000 The Extent and Cause of the Pre White Dwarf Instability Strip The Astrophysical Journal 532 2 1078 1088 arXiv astro ph 9910495 Bibcode 2000ApJ 532 1078O doi 10 1086 308613 S2CID 115958740 Winget D E 1998 Asteroseismology of white dwarf stars Journal of Physics Condensed Matter 10 49 11247 11261 Bibcode 1998JPCM 1011247W doi 10 1088 0953 8984 10 49 014 S2CID 250749380 a b Heger A Fryer C L Woosley S E Langer N Hartmann D H 2003 How Massive Single Stars End Their Life The Astrophysical Journal 591 1 288 300 arXiv astro ph 0212469 Bibcode 2003ApJ 591 288H doi 10 1086 375341 S2CID 59065632 Napiwotzki Ralf 2009 The galactic population of white dwarfs Journal of Physics Conference Series 172 1 012004 arXiv 0903 2159 Bibcode 2009JPhCS 172a2004N doi 10 1088 1742 6596 172 1 012004 S2CID 17521113 Laughlin G Bodenheimer P Adams Fred C 1997 The End of the Main Sequence The Astrophysical Journal 482 1 420 432 Bibcode 1997ApJ 482 420L doi 10 1086 304125 a b Jeffery Simon Stars Beyond Maturity Archived from the original on 4 April 2015 Retrieved 3 May 2007 Sarna M J Ergma E Gerskevits J 2001 Helium core white dwarf evolution including white dwarf companions to neutron stars Astronomische Nachrichten 322 5 6 405 410 Bibcode 2001AN 322 405S doi 10 1002 1521 3994 200112 322 5 6 lt 405 AID ASNA405 gt 3 0 CO 2 6 Benvenuto O G De Vito M A 2005 The formation of helium white dwarfs in close binary systems II Monthly Notices of the Royal Astronomical Society 362 3 891 905 Bibcode 2005MNRAS 362 891B doi 10 1111 j 1365 2966 2005 09315 x Nelemans G Tauris T M 1998 Formation of undermassive single white dwarfs and the influence of planets on late stellar evolution Astronomy and Astrophysics 335 L85 arXiv astro ph 9806011 Bibcode 1998A amp A 335L 85N Planet diet helps white dwarfs stay young and trim New Scientist No 2639 18 January 2008 Archived from the original on 20 April 2010 Retrieved 18 September 2017 Dhillon Vik The evolution of low mass stars lecture notes Physics 213 University of Sheffield Archived from the original on 7 November 2012 Retrieved 3 May 2007 Dhillon Vik The evolution of high mass stars lecture notes Physics 213 University of Sheffield Archived from the original on 7 November 2012 Retrieved 3 May 2007 Schaffner Bielich Jurgen 2005 Strange quark matter in stars A general overview Journal of Physics G Nuclear and Particle Physics 31 6 S651 S657 arXiv astro ph 0412215 Bibcode 2005JPhG 31S 651S doi 10 1088 0954 3899 31 6 004 S2CID 118886040 Nomoto K 1984 Evolution of 8 10 solar mass stars toward electron capture supernovae I Formation of electron degenerate O NE MG cores The Astrophysical Journal 277 791 Bibcode 1984ApJ 277 791N doi 10 1086 161749 Woosley S E Heger A Weaver T A 2002 The evolution and explosion of massive stars Reviews of Modern Physics 74 4 1015 1071 Bibcode 2002RvMP 74 1015W doi 10 1103 RevModPhys 74 1015 Werner K Rauch T Barstow M A Kruk J W 2004 Chandra and FUSE spectroscopy of the hot bare stellar core H 1504 65 Astronomy and Astrophysics 421 3 1169 1183 arXiv astro ph 0404325 Bibcode 2004A amp A 421 1169W doi 10 1051 0004 6361 20047154 S2CID 2983893 Livio Mario Truran James W 1994 On the interpretation and implications of nova abundances An abundance of riches or an overabundance of enrichments The Astrophysical Journal 425 797 Bibcode 1994ApJ 425 797L doi 10 1086 174024 Jordan George C IV Perets Hagai B Fisher Robert T van Rossum Daniel R 2012 Failed detonation Supernovae Subluminous Low velocity Ia Supernovae and their Kicked Remnant White Dwarfs with Iron rich Cores The Astrophysical Journal Letters 761 2 L23 arXiv 1208 5069 Bibcode 2012ApJ 761L 23J doi 10 1088 2041 8205 761 2 L23 S2CID 119203015 Panei J A Althaus L G Benvenuto O G 2000 The evolution of iron core white dwarfs Monthly Notices of the Royal Astronomical Society 312 3 531 539 arXiv astro ph 9911371 Bibcode 2000MNRAS 312 531P doi 10 1046 j 1365 8711 2000 03236 x S2CID 17854858 a b c Adams Fred C Laughlin Gregory 1997 A dying universe The long term fate and evolution of astrophysical objects Reviews of Modern Physics 69 2 337 372 arXiv astro ph 9701131 Bibcode 1997RvMP 69 337A doi 10 1103 RevModPhys 69 337 S2CID 12173790 Seager S Kuchner M Hier Majumder C Militzer B 19 July 2007 Mass Radius Relationships for Solid Exoplanets The Astrophysical Journal published November 2007 669 2 1279 1297 arXiv 0707 2895 Bibcode 2007ApJ 669 1279S doi 10 1086 521346 S2CID 8369390 Lemonick Michael 26 August 2011 Scientists Discover a Diamond as Big as a Planet Time Magazine Archived from the original on 24 August 2013 Retrieved 18 June 2015 Hubble finds dead stars polluted with planetary debris ESA Hubble Press Release Archived from the original on 9 June 2013 Retrieved 10 May 2013 Comet falling into white dwarf artist s impression www spacetelescope org Archived from the original on 15 February 2017 Retrieved 14 February 2017 Koester D Gansicke B T Farihi J 1 June 2014 The frequency of planetary debris around young white dwarfs Astronomy and Astrophysics 566 A34 arXiv 1404 2617 Bibcode 2014A amp A 566A 34K doi 10 1051 0004 6361 201423691 ISSN 0004 6361 S2CID 119268896 Jura M 1 May 2008 Pollution of Single White Dwarfs by Accretion of Many Small Asteroids The Astronomical Journal 135 5 1785 1792 arXiv 0802 4075 Bibcode 2008AJ 135 1785J doi 10 1088 0004 6256 135 5 1785 ISSN 0004 6256 S2CID 16571761 a b c Debes John H Thevenot Melina Kuchner Marc J Burgasser Adam J Schneider Adam C Meisner Aaron M Gagne Jonathan Faherty Jacqueline K Rees Jon M 19 February 2019 A 3 Gyr White Dwarf with Warm Dust Discovered via the Backyard Worlds Planet 9 Citizen Science Project The Astrophysical Journal 872 2 L25 arXiv 1902 07073 Bibcode 2019ApJ 872L 25D doi 10 3847 2041 8213 ab0426 ISSN 2041 8213 S2CID 119359995 van Maanen A 1 December 1917 Two Faint Stars with Large Proper Motion Publications of the Astronomical Society of the Pacific 29 172 258 Bibcode 1917PASP 29 258V doi 10 1086 122654 ISSN 0004 6280 S2CID 250734202 a b Klein Beth L Doyle Alexandra E Zuckerman B Dufour P Blouin Simon Melis Carl Weinberger Alycia J Young Edward D 1 June 2021 Discovery of Beryllium in White Dwarfs Polluted by Planetesimal Accretion The Astrophysical Journal 914 1 61 arXiv 2102 01834 Bibcode 2021ApJ 914 61K doi 10 3847 1538 4357 abe40b ISSN 0004 637X S2CID 231786441 Zuckerman B 1 June 2015 Recognition of the First Observational Evidence of an Extrasolar Planetary System 19Th European Workshop on White Dwarfs Vol 493 p 291 Bibcode 2015ASPC 493 291Z Farihi J 1 April 2016 Circumstellar debris and pollution at white dwarf stars New Astronomy Reviews 71 9 34 arXiv 1604 03092 Bibcode 2016NewAR 71 9F doi 10 1016 j newar 2016 03 001 ISSN 1387 6473 S2CID 118486264 Zuckerman B Becklin E E 1 November 1987 Excess infrared radiation from a white dwarf an orbiting brown dwarf Nature 330 6144 138 140 Bibcode 1987Natur 330 138Z doi 10 1038 330138a0 ISSN 0028 0836 S2CID 4357883 a b Reach William T Kuchner Marc J Von Hippel Ted Burrows Adam Mullally Fergal Kilic Mukremin Winget D E 2005 The Dust Cloud around the White Dwarf G29 38 The Astrophysical Journal 635 2 L161 arXiv astro ph 0511358 Bibcode 2005ApJ 635L 161R doi 10 1086 499561 S2CID 119462589 Steckloff Jordan K Debes John Steele Amy Johnson Brandon Adams Elisabeth R Jacobson Seth A Springmann Alessondra 1 June 2021 How Sublimation Delays the Onset of Dusty Debris Disk Formation around White Dwarf Stars The Astrophysical Journal 913 2 L31 arXiv 2104 14035 Bibcode 2021ApJ 913L 31S doi 10 3847 2041 8213 abfd39 ISSN 0004 637X PMC 8740607 PMID 35003618 a b Veras Dimitri 1 October 2021 Planetary Systems Around White Dwarfs Bibcode 2021orel bookE 1V Sanderson Hannah Bonsor Amy Mustill Alexander J 1 June 2022 The galactic population of white dwarfs Journal of Physics Conference Series 172 1 012004 arXiv 0903 2159 Bibcode 2009JPhCS 172a2004N doi 10 1088 1742 6596 172 1 012004 S2CID 250666952 Mullally Susan Elizabeth Mullally Fergal Albert Loic Barclay Thomas Debes John Henry Kilic Mukremin Kuchner Marc Jason Quintana Elisa V Reach William 2021 A Search for the Giant Planets that Drive White Dwarf Accretion JWST Proposal Cycle 1 1911 Bibcode 2021jwst prop 1911M Comet clash kicks up dusty haze BBC News 13 February 2007 Archived from the original on 16 February 2007 Retrieved 20 September 2007 Su K Y L Chu Y H Rieke G H Huggins P J Gruendl R Napiwotzki R Rauch T Latter W B Volk K 2007 A Debris Disk around the Central Star of the Helix Nebula The Astrophysical Journal 657 1 L41 arXiv astro ph 0702296 Bibcode 2007ApJ 657L 41S doi 10 1086 513018 S2CID 15244406 Sion Edward M Holberg J B Oswalt Terry D McCook George P Wasatonic Richard 2009 The White Dwarfs Within 20 Parsecs of the Sun Kinematics and Statistics The Astronomical Journal 138 6 1681 1689 arXiv 0910 1288 Bibcode 2009AJ 138 1681S doi 10 1088 0004 6256 138 6 1681 S2CID 119284418 Li Jianke Ferrario Lilia Wickramasinghe Dayal 1998 Planets around White Dwarfs Astrophysical Journal Letters 503 1 L151 Bibcode 1998ApJ 503L 151L doi 10 1086 311546 p L51 Debes John H Walsh Kevin J Stark Christopher 24 February 2012 The Link Between Planetary Systems Dusty White Dwarfs and Metal Polluted White Dwarfs The Astrophysical Journal 747 2 148 arXiv 1201 0756 Bibcode 2012ApJ 747 148D doi 10 1088 0004 637X 747 2 148 ISSN 0004 637X S2CID 118688656 Veras Dimitri Gansicke Boris T 21 February 2015 Detectable close in planets around white dwarfs through late unpacking Monthly Notices of the Royal Astronomical Society 447 2 1049 1058 arXiv 1411 6012 Bibcode 2015MNRAS 447 1049V doi 10 1093 mnras stu2475 ISSN 0035 8711 S2CID 119279872 Frewen S F N Hansen B M S 11 April 2014 Eccentric planets and stellar evolution as a cause of polluted white dwarfs Monthly Notices of the Royal Astronomical Society 439 3 2442 2458 arXiv 1401 5470 Bibcode 2014MNRAS 439 2442F doi 10 1093 mnras stu097 ISSN 0035 8711 S2CID 119257046 Bonsor Amy Gansicke Boris T Veras Dimitri Villaver Eva Mustill Alexander J 21 May 2018 Unstable low mass planetary systems as drivers of white dwarf pollution Monthly Notices of the Royal Astronomical Society 476 3 3939 3955 arXiv 1711 02940 Bibcode 2018MNRAS 476 3939M doi 10 1093 mnras sty446 ISSN 0035 8711 S2CID 4809366 Gansicke Boris T Holman Matthew J Veras Dimitri Payne Matthew J 21 March 2016 Liberating exomoons in white dwarf planetary systems Monthly Notices of the Royal Astronomical Society 457 1 217 231 arXiv 1603 09344 Bibcode 2016MNRAS 457 217P doi 10 1093 mnras stv2966 ISSN 0035 8711 S2CID 56091285 Rebassa Mansergas Alberto Xu 许偲艺 Siyi Veras Dimitri 21 January 2018 The critical binary star separation for a planetary system origin of white dwarf pollution Monthly Notices of the Royal Astronomical Society 473 3 2871 2880 arXiv 1708 05391 Bibcode 2018MNRAS 473 2871V doi 10 1093 mnras stx2141 ISSN 0035 8711 S2CID 55764122 Becklin E E Zuckerman B Farihi J 10 February 2008 Spitzer IRAC Observations of White Dwarfs I Warm Dust at Metal Rich Degenerates The Astrophysical Journal 674 1 431 446 arXiv 0710 0907 Bibcode 2008ApJ 674 431F doi 10 1086 521715 ISSN 0004 637X S2CID 17813180 Sigurdsson Steinn Richer Harvey B Hansen Brad M Stairs Ingrid H Thorsett Stephen E 1 July 2003 A Young White Dwarf Companion to Pulsar B1620 26 Evidence for Early Planet Formation Science 301 5630 193 196 arXiv astro ph 0307339 Bibcode 2003Sci 301 193S doi 10 1126 science 1086326 ISSN 0036 8075 PMID 12855802 S2CID 39446560 Hardy Adam Schreiber Matthias R Parsons Steven G Caceres Claudio Brinkworth Carolyn Veras Dimitri Gansicke Boris T Marsh Thomas R Cieza Lucas 1 July 2016 The detection of dust around NN Ser Monthly Notices of the Royal Astronomical Society 459 4 4518 4526 arXiv 1604 05808 Bibcode 2016MNRAS 459 4518H doi 10 1093 mnras stw976 ISSN 0035 8711 Beuermann K Hessman F V Dreizler S Marsh T R Parsons S G Winget D E Miller G F Schreiber M R Kley W Dhillon V S Littlefair S P Copperwheat C M Hermes J J 1 October 2010 Two planets orbiting the recently formed post common envelope binary NN Serpentis Astronomy and Astrophysics 521 L60 arXiv 1010 3608 Bibcode 2010A amp A 521L 60B doi 10 1051 0004 6361 201015472 ISSN 0004 6361 S2CID 53702506 Luhman K L Burgasser A J Bochanski J J 1 March 2011 Discovery of a Candidate for the Coolest Known Brown Dwarf The Astrophysical Journal 730 1 L9 arXiv 1102 5411 Bibcode 2011ApJ 730L 9L doi 10 1088 2041 8205 730 1 L9 hdl 1721 1 95646 ISSN 0004 637X S2CID 54666396 Leggett S K Tremblin P Esplin T L Luhman K L Morley Caroline V 1 June 2017 The Y type Brown Dwarfs Estimates of Mass and Age from New Astrometry Homogenized Photometry and Near infrared Spectroscopy The Astrophysical Journal 842 2 118 arXiv 1704 03573 Bibcode 2017ApJ 842 118L doi 10 3847 1538 4357 aa6fb5 ISSN 0004 637X S2CID 119249195 a b Gansicke Boris T Schreiber Matthias R Toloza Odette Gentile Fusillo Nicola P Koester Detlev Manser Christopher J Accretion of a giant planet onto a white dwarf PDF ESO Archived PDF from the original on 4 December 2019 Retrieved 11 December 2019 Xu Siyi Diamond Lowe Hannah MacDonald Ryan J Vanderburg Andrew Blouin Simon Dufour P Gao Peter Kreidberg Laura Leggett S K Mann Andrew W Morley Caroline V Stephens Andrew W O Connor Christopher E Thao Pa Chia Lewis Nikole K 1 December 2021 Gemini GMOS Transmission Spectroscopy of the Grazing Planet Candidate WD 1856 534 b The Astronomical Journal 162 6 296 arXiv 2110 14106 Bibcode 2021AJ 162 296X doi 10 3847 1538 3881 ac2d26 ISSN 0004 6256 S2CID 239998664 Vanderburg Andrew et al 16 September 2020 A giant planet candidate transiting a white dwarf Nature 585 7825 363 367 arXiv 2009 07282 Bibcode 2020Natur 585 363V doi 10 1038 s41586 020 2713 y hdl 1721 1 129733 PMID 32939071 S2CID 221738865 Chou Felicia Andreoli Claire Cofield Calia 16 September 2020 NASA Missions Spy First Possible Planet Hugging a Stellar Cinder NASA Gary Bruce L 17 September 2020 WD 1856 534 Transit Light Curve Photometry BruceGary net Retrieved 17 September 2020 Rappaport S Gary B L Vanderburg A Xu S Pooley D Mukai K 1 February 2018 WD 1145 017 optical activity during 2016 2017 and limits on the X ray flux Monthly Notices of the Royal Astronomical Society 474 1 933 946 arXiv 1709 08195 Bibcode 2018MNRAS 474 933R doi 10 1093 mnras stx2663 ISSN 0035 8711 a b c d Vanderburg Andrew Johnson John Asher Rappaport Saul Bieryla Allyson Irwin Jonathan Lewis John Arban Kipping David Brown Warren R Dufour Patrick 22 October 2015 A disintegrating minor planet transiting a white dwarf Nature 526 7574 546 549 arXiv 1510 06387 Bibcode 2015Natur 526 546V doi 10 1038 nature15527 PMID 26490620 S2CID 4451207 Manser Christopher J Gansicke Boris T Eggl Siegfried Hollands Mark Izquierdo Paula Koester Detlev Landstreet John D Lyra Wladimir Marsh Thomas R Meru Farzana Mustill Alexander J Rodriguez Gil Pablo Toloza Odette Veras Dimitri Wilson David J 1 April 2019 A planetesimal orbiting within the debris disc around a white dwarf star Science 364 6435 66 69 arXiv 1904 02163 Bibcode 2019Sci 364 66M doi 10 1126 science aat5330 ISSN 0036 8075 PMID 30948547 S2CID 96434522 Swan Andrew Kenyon Scott J Farihi Jay Dennihy Erik Gansicke Boris T Hermes J J Melis Carl von Hippel Ted 1 September 2021 Collisions in a gas rich white dwarf planetary debris disc Monthly Notices of the Royal Astronomical Society 506 1 432 440 arXiv 2106 09025 Bibcode 2021MNRAS 506 432S doi 10 1093 mnras stab1738 ISSN 0035 8711 PMC 8263348 PMID 34248393 a b Wang Ting Gui Jiang Ning Ge Jian Cutri Roc M Jiang Peng Sheng Zhengfeng Zhou Hongyan Bauer James Mainzer Amy Wright Edward L 9 October 2019 An On going Mid infrared Outburst in the White Dwarf 0145 234 Catching in Action of Tidal Disruption of an Exoasteroid arXiv 1910 04314 astro ph SR Vanderbosch Z Hermes J J Dennihy E Dunlap B H Izquierdo P Tremblay P E Cho P B Gansicke B T Toloza O Bell K J Montgomery M H Winget D E 1 July 2020 A White Dwarf with Transiting Circumstellar Material Far outside the Roche Limit The Astrophysical Journal 897 2 171 arXiv 1908 09839 Bibcode 2020ApJ 897 171V doi 10 3847 1538 4357 ab9649 ISSN 0004 637X S2CID 219941489 Veras Dimitri McDonald Catriona H Makarov Valeri V 1 March 2020 Constraining the origin of the planetary debris surrounding ZTF J0139 5245 through rotational fission of a triaxial asteroid Monthly Notices of the Royal Astronomical Society 492 4 5291 5296 arXiv 2001 08223 Bibcode 2020MNRAS 492 5291V doi 10 1093 mnras staa243 ISSN 0035 8711 Guidry Joseph A Vanderbosch Zachary P Hermes J J Barlow Brad N Lopez Isaac D Boudreaux Thomas M Corcoran Kyle A Bell Keaton J Montgomery M H Heintz Tyler M Castanheira Barbara G Reding Joshua S Dunlap Bart H Winget D E Winget Karen I 1 May 2021 I Spy Transits and Pulsations Empirical Variability in White Dwarfs Using Gaia and the Zwicky Transient Facility The Astrophysical Journal 912 2 125 arXiv 2012 00035 Bibcode 2021ApJ 912 125G doi 10 3847 1538 4357 abee68 ISSN 0004 637X S2CID 227238802 Vanderbosch Zachary P Rappaport Saul Guidry Joseph A Gary Bruce L Blouin Simon Kaye Thomas G Weinberger Alycia J Melis Carl Klein Beth L Zuckerman B Vanderburg Andrew Hermes J J Hegedus Ryan J Burleigh Matthew R Sefako Ramotholo 1 August 2021 Recurring Planetary Debris Transits and Circumstellar Gas around White Dwarf ZTF J0328 1219 The Astrophysical Journal 917 1 41 arXiv 2106 02659 Bibcode 2021ApJ 917 41V doi 10 3847 1538 4357 ac0822 ISSN 0004 637X S2CID 235358242 Lemonick Michael D 21 October 2015 Zombie Star Caught Feasting on Asteroids National Geographic News Archived from the original on 24 October 2015 Retrieved 22 October 2015 Agol Eric 2011 Transit Surveys for Earths in the Habitable Zones of White Dwarfs The Astrophysical Journal Letters 635 2 L31 arXiv 1103 2791 Bibcode 2011ApJ 731L 31A doi 10 1088 2041 8205 731 2 L31 S2CID 118739494 Barnes Rory Heller Rene 2011 Habitable Planets Around White and Brown Dwarfs The Perils of a Cooling Primary Astrobiology 13 3 279 291 arXiv 1211 6467 Bibcode 2013AsBio 13 279B doi 10 1089 ast 2012 0867 PMC 3612282 PMID 23537137 Nordhaus J Spiegel D S 2013 On the orbits of low mass companions to white dwarfs and the fates of the known exoplanets Monthly Notices of the Royal Astronomical Society 432 1 500 505 arXiv 1211 1013 Bibcode 2013MNRAS 432 500N doi 10 1093 mnras stt569 S2CID 119227364 Di Stefano R Nelson L A Lee W Wood T H Rappaport S 1997 Luminous Supersoft X ray Sources as Type Ia Progenitors In P Ruiz Lapuente R Canal J Isern eds Thermonuclear supernovae Nato Advanced Science Institutes Asi Series C NATO ASI series Mathematical and physical sciences Vol 486 Springer pp 148 149 Bibcode 1997ASIC 486 147D doi 10 1007 978 94 011 5710 0 10 ISBN 978 0 7923 4359 2 Lopes de Oliveira R Bruch A Rodrigues C V de Oliveira A S Mukai K 2020 CTCV J2056 3014 An X Ray faint Intermediate Polar Harboring an Extremely Fast spinning White Dwarf The Astrophysical Journal Letters 898 2 L40 arXiv 2007 13932 Bibcode 2020ApJ 898L 40L doi 10 3847 2041 8213 aba618 S2CID 220831174 Aguilar David A Pulliam Christine 16 November 2010 Astronomers Discover Merging Star Systems that Might Explode Harvard Smithsonian Center for Astrophysics Archived from the original on 9 April 2011 Retrieved 16 February 2011 Aguilar David A Pulliam Christine 13 July 2011 Evolved Stars Locked in Fatalistic Dance Harvard Smithsonian Center for Astrophysics Archived from the original on 15 July 2011 Retrieved 17 July 2011 Yoon S C Langer N 2004 Presupernova evolution of accreting white dwarfs with rotation Astronomy and Astrophysics 419 2 623 644 arXiv astro ph 0402287 Bibcode 2004A amp A 419 623Y doi 10 1051 0004 6361 20035822 S2CID 2963085 Blinnikov S I Ropke F K Sorokina E I Gieseler M Reinecke M Travaglio C Hillebrandt W Stritzinger M 2006 Theoretical light curves for deflagration models of type Ia supernova Astronomy and Astrophysics 453 1 229 240 arXiv astro ph 0603036 Bibcode 2006A amp A 453 229B doi 10 1051 0004 6361 20054594 S2CID 15493284 O Neill Ian 6 September 2011 Don t slow down white dwarf you might explode Discovery Communications LLC Archived from the original on 24 January 2012 Gonzalez Hernandez J I Ruiz Lapuente P Tabernero H M Montes D Canal R Mendez J Bedin L R 2012 No surviving evolved companions of the progenitor of SN 1006 Nature 489 7417 533 536 arXiv 1210 1948 Bibcode 2012Natur 489 533G doi 10 1038 nature11447 PMID 23018963 S2CID 4431391 Krause Oliver et al 2008 Tycho Brahe s 1572 supernova as a standard type Ia as revealed by its light echo spectrum Nature 456 7222 617 619 arXiv 0810 5106 Bibcode 2008Natur 456 617K doi 10 1038 nature07608 PMID 19052622 S2CID 4409995 de la Fuente Marcos Raul de la Fuente Marcos Carlos 2022 Deep and fast Solar System flybys The controversial case of WD 0810 353 Astronomy amp Astrophysics EDP Sciences arXiv 2210 04863 Bibcode 2022arXiv221004863D doi 10 1051 0004 6361 202245020 ISSN 0004 6361 S2CID 252863734 Cataclysmic Variables fact sheet Imagine the Universe NASA Goddard Archived from the original on 9 July 2007 Retrieved 4 May 2007 a b Introduction to Cataclysmic Variables CVs fact sheet NASA Goddard Archived from the original on 6 February 2012 Retrieved 4 May 2007 Giammichele N Bergeron P Dufour P April 2012 Know Your Neighborhood A Detailed Model Atmosphere Analysis of Nearby White Dwarfs The Astrophysical Journal Supplement 199 2 35 arXiv 1202 5581 Bibcode 2012ApJS 199 29G doi 10 1088 0067 0049 199 2 29 S2CID 118304737 29 Delfosse Xavier et al April 1999 New neighbours I 13 new companions to nearby M dwarfs Astronomy and Astrophysics 344 897 910 arXiv astro ph 9812008 Bibcode 1999A amp A 344 897D Rocky Exoplanets Are Even Stranger Than We Thought Retrieved 2 December 2021 Cosmic Spider Found to Be Source of Powerful Gamma Rays Retrieved 13 December 2022 Citizen Scientist Leads Discovery of 34 Ultracool Dwarf Binaries Using Archive at NSF s NOIRLab Retrieved 16 December 2022 External links and further reading Edit Wikimedia Commons has media related to White dwarfs General Kawaler S D 1997 White Dwarf Stars In Kawaler S D Novikov I Srinivasan G eds Stellar remnants 1997 ISBN 978 3 540 61520 0 Kepler S O et al February 2015 New white dwarf stars in the Sloan Digital Sky Survey Data Release 10 Monthly Notices of the Royal Astronomical Society 446 4 4078 4087 arXiv 1411 4149 Bibcode 2015MNRAS 446 4078K doi 10 1093 mnras stu2388 ISSN 1365 2966 Rebassa Mansergas A Gansicke B T Rodriguez Gil P Schreiber M R Koester D 28 November 2007 Post common envelope binaries from SDSS I 101 white dwarf main sequence binaries with multiple Sloan Digital Sky Survey spectroscopy Post common envelope binaries from SDSS Monthly Notices of the Royal Astronomical Society 382 4 1377 1393 doi 10 1111 j 1365 2966 2007 12288 x Physics Black holes white dwarfs and neutron stars the physics of compact objects Stuart L Shapiro and Saul A Teukolsky New York Wiley 1983 ISBN 0 471 87317 9 Gentile Dave 1995 White dwarf stars and the Chandrasekhar limit Master s thesis DePaul University Estimating Stellar Parameters from Energy Equipartition sciencebits com Discusses how to find mass radius relations and mass limits for white dwarfs using simple energy arguments Variability Winget D E 1998 Asteroseismology of white dwarf stars Journal of Physics Condensed Matter 10 49 11247 11261 Bibcode 1998JPCM 1011247W doi 10 1088 0953 8984 10 49 014 S2CID 250749380 Magnetic field Wickramasinghe D T Ferrario Lilia 2000 Magnetism in Isolated and Binary White Dwarfs Publications of the Astronomical Society of the Pacific 112 773 873 924 Bibcode 2000PASP 112 873W doi 10 1086 316593 Frequency Gibson B K Flynn C 2001 White Dwarfs and Dark Matter Science 292 5525 2211a arXiv astro ph 0104255 doi 10 1126 science 292 5525 2211a PMID 11423620 S2CID 14080941 Observational Provencal J L Shipman H L Hog Erik Thejll P 1998 Testing the White Dwarf Mass Radius Relation with Hipparcos The Astrophysical Journal 494 2 759 767 Bibcode 1998ApJ 494 759P doi 10 1086 305238 Gates Evalyn Gyuk Geza Harris Hugh C Subbarao Mark Anderson Scott Kleinman S J Liebert James Brewington Howard et al 2004 Discovery of New Ultracool White Dwarfs in the Sloan Digital Sky Survey The Astrophysical Journal 612 2 L129 arXiv astro ph 0405566 Bibcode 2004ApJ 612L 129G doi 10 1086 424568 S2CID 7570539 McCook G P Sion E M eds White Dwarf Catalogue WD Villanova University Dufour P Liebert James Fontaine G Behara N 2007 White dwarf stars with carbon atmospheres Nature 450 7169 522 4 arXiv 0711 3227 Bibcode 2007Natur 450 522D doi 10 1038 nature06318 PMID 18033290 S2CID 4398697 Images Astronomy Picture of the Day NGC 2440 Cocoon of a New White Dwarf Astronomy Picture of the Day photograph NASA 21 February 2010 Dust and the Helix Nebula Astronomy Picture of the Day photograph NASA 31 December 2009 The Helix Nebula from La Silla Observatory Astronomy Picture of the Day photograph NASA 3 March 2009 IC 4406 A Seemingly Square Nebula Astronomy Picture of the Day photograph NASA 27 July 2008 A Nearby Supernova in Spiral Galaxy M100 Astronomy Picture of the Day photograph NASA 7 March 2006 White Dwarf Star Spiral Astronomy Picture of the Day photograph NASA 1 June 2005 Portals Physics Astronomy Stars Spaceflight img, wikipedia, wiki, book, books, library,

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