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Capella

Capella is the brightest star in the northern constellation of Auriga. It has the Bayer designation α Aurigae, which is Latinised to Alpha Aurigae and abbreviated Alpha Aur or α Aur. Capella is the sixth-brightest star in the night sky, and the third-brightest in the northern celestial hemisphere after Arcturus and Vega. A prominent object in the northern winter sky, it is circumpolar to observers north of 44°N. Its name meaning "little goat" in Latin, Capella depicted the goat Amalthea that suckled Zeus in classical mythology. Capella is relatively close, at 42.9 light-years (13.2 pc) from the Sun. It is one of the brightest X-ray sources in the sky, thought to come primarily from the corona of Capella Aa.

Capella
Location of Capella Aa, as the brightest star (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Auriga
Pronunciation /kəˈpɛlə/[1]
A
Right ascension 05h 16m 41.35871s[2][note 1]
Declination +45° 59′ 52.7693″[2][note 1]
Apparent magnitude (V) +0.08[3] (+0.03 – +0.16[4])
H
Right ascension 05h 17m 23.728s[5]
Declination +45° 50′ 22.97″[5]
Apparent magnitude (V) 10.16[6]
L
Right ascension 05h 17m 23.943s[7]
Declination +45° 50′ 19.84″[7]
Apparent magnitude (V) 13.7[8]
Characteristics
A
Spectral type G3III:[9]
U−B color index +0.44[3]
B−V color index +0.80[3]
V−R color index −0.3[3]
R−I color index +0.44[3]
Variable type RS CVn[10] (suspected[11])
Aa
Evolutionary stage Red clump[12]
Spectral type K0III[13]
Ab
Evolutionary stage Subgiant[12]
Spectral type G1III[13]
H
Evolutionary stage Main sequence (red dwarf)[14]
Spectral type M2.5 V[15]
U−B color index 1.24[16]
B−V color index 1.50[14]
R−I color index 0.91[14]
L
Evolutionary stage Main sequence (red dwarf)
Spectral type M4:[17]
Astrometry
A
Radial velocity (Rv)+29.9387±0.0032[12] km/s
Proper motion (μ) RA: 75.52[2] mas/yr
Dec.: −427.11[2] mas/yr
Parallax (π)76.20 ± 0.46 mas[2]
Distance42.919±0.049 ly
(13.159±0.015[12] pc)
Aa
Absolute magnitude (MV)+0.296[12]
Ab
Absolute magnitude (MV)+0.167[12]
HL
Radial velocity (Rv)31.63±0.14[12] km/s
H
Proper motion (μ) RA: 88.57[18] mas/yr
Dec.: −428.91[18] mas/yr
Parallax (π)74.9521 ± 0.0188 mas[19]
Distance43.52 ± 0.01 ly
(13.342 ± 0.003 pc)
Absolute magnitude (MV)9.53[20]
L
Proper motion (μ) RA: 54.1[21] mas/yr
Dec.: −417.5[21] mas/yr
Parallax (π)75.1838 ± 0.0534 mas[22]
Distance43.38 ± 0.03 ly
(13.301 ± 0.009 pc)
Absolute magnitude (MV)13.1[23]
Orbit[12]
PrimaryAa
CompanionAb
Period (P)104.02128±0.00016 d
Semi-major axis (a)0.056442±0.000023"
(0.74272±0.00069 AU)
Eccentricity (e)0.00089±0.00011
Inclination (i)137.156±0.046°
Longitude of the node (Ω)40.522±0.039°
Periastron epoch (T)2,448,147.6±2.6 JD
Argument of periastron (ω)
(primary)
342.6±9.0 JD°
Semi-amplitude (K1)
(primary)
25.9611±0.0044 km/s
Semi-amplitude (K2)
(secondary)
26.860±0.0017 km/s
Orbit[12]
PrimaryH
CompanionL
Period (P)300 yr
Semi-major axis (a)3.5"
(40 AU[24])
Eccentricity (e)0.75
Inclination (i)52°
Longitude of the node (Ω)288°
Periastron epoch (T)2,220
Argument of periastron (ω)
(secondary)
88°
Details[12]
A
Metallicity [Fe/H]−0.04±0.06 dex
Age590–650 Myr
Aa
Mass2.5687±0.0074 M
Radius11.98±0.57 R
Luminosity (bolometric)78.7±4.2 L
Surface gravity (log g)2.691±0.041 cgs
Temperature4,970±50 K
Rotation104±3 days
Rotational velocity (v sin i)4.1±0.4 km/s
Ab
Mass2.4828±0.0067 M
Radius8.83±0.33 R
Luminosity (bolometric)72.7±3.6 L
Surface gravity (log g)2.941±0.032 cgs
Temperature5,730±60 K
Rotation8.5±0.2 days
Rotational velocity (v sin i)35.0±0.5 km/s
H
Mass0.57[12][24] M
Radius0.54±0.03[20] R
Luminosity (bolometric)0.05[20] L
Surface gravity (log g)4.75±0.05 cgs
Temperature3,700±150[20] K
Metallicity [Fe/H]+0.1[20] dex
L
Mass0.53[12] M
Other designations
Alhajoth, Hokulei, α Aurigae, 13 Aurigae, BD+45 1077, FK5 193, GC 6427, HD 34029, HIP 24608, HR 1708, SAO 40186, PPM 47925, ADS 3841, CCDM J05168+4559, WDS 05167+4600, LTT 11619, NLTT 14766[25][3][26][27][16]
A: GJ 194
HL: GJ 195[16]
H: PPM 47938, G 96-29, LTT 11622, NLTT 14788, 2MASS J05172386+4550229[28]
L: 2MASS J05172394+4550198[29]
Database references
SIMBADCapella
Capella H
Capella L

Although it appears to be a single star to the naked eye, Capella is actually a quadruple star system organized in two binary pairs, made up of the stars Capella Aa, Capella Ab, Capella H and Capella L. The primary pair, Capella Aa and Capella Ab, are two bright-yellow giant stars, both of which are around 2.5 times as massive as the Sun. The secondary pair, Capella H and Capella L, are around 10,000 astronomical units (AU)[note 2] from the first and are two faint, small and relatively cool red dwarfs.

Capella Aa and Capella Ab have exhausted their core hydrogen, and cooled and expanded, moving off the main sequence. They are in a very tight circular orbit about 0.74 AU apart, and orbit each other every 104 days. Capella Aa is the cooler and more luminous of the two with spectral class K0III; it is 78.7 ± 4.2 times the Sun's luminosity and 11.98 ± 0.57 times its radius. An aging red clump star, it is fusing helium to carbon and oxygen in its core. Capella Ab is slightly smaller and hotter and of spectral class G1III; it is 72.7 ± 3.6 times as luminous as the Sun and 8.83 ± 0.33 times its radius. It is in the Hertzsprung gap, corresponding to a brief subgiant evolutionary phase as it expands and cools to become a red giant. Several other stars in the same visual field have been catalogued as companions but are physically unrelated.

Nomenclature edit

 
Capella is the brightest star in the constellation of Auriga (upper left).

α Aurigae (Latinised to Alpha Aurigae) is the star system's Bayer designation. It also has the Flamsteed designation 13 Aurigae. It is listed in several multiple star catalogues as ADS 3841, CCDM J05168+4559, and WDS J05167+4600. As a relatively nearby star system, Capella is listed in the Gliese-Jahreiss Catalogue with designations GJ 194 for the bright pair of giants and GJ 195 for the faint pair of red dwarfs.

The traditional name Capella is Latin for (small) female goat; the alternative name Capra was more commonly used in classical times.[30] It is the translation of the Greek star name Aἴξ (aix) meaning "the Goat". As the sound of the Greek term for the goat (aἴξ) is similar to the sound of the name for the Aegaean Sea, this star has been used for weather rules and determining the seasonal wind direction.[31] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[32] to catalogue and standardize proper names for stars. The WGSN's first bulletin of July 2016[33] included a table of the first two batches of names approved by the WGSN; which included Capella for this star. It is now so entered in the IAU Catalog of Star Names.[34] The catalogue of star names lists Capella as applying to the star α Aurigae Aa.[35]

Observational history edit

Capella was the brightest star in the night sky from 210,000 years ago to 160,000 years ago, at about −1.8 in apparent magnitude. At −1.1, Aldebaran was brightest before this period; it and Capella were situated rather close to each other in the sky and approximated boreal pole stars at the time.[36]

 
Building J (foreground) at Monte Albán

Capella is thought to be mentioned in an Akkadian inscription dating to the 20th century BC.[37] Its goat-associated symbolism dates back to Mesopotamia as a constellation called "GAM", "Gamlum" or "MUL.GAM" in the 7th-century BC document MUL.APIN. GAM represented a scimitar or crook and may have represented the star alone or the constellation of Auriga as a whole. Later, Bedouin astronomers created constellations that were groups of animals, where each star represented one animal. The stars of Auriga comprised a herd of goats, an association also present in Greek mythology.[38] It is sometimes called the Shepherd's Star in English literature.[39] Capella was seen as a portent of rain in classical times.[40]

Building J of the pre-Columbian site Monte Albán in Oaxaca state in Mexico was built around 275 BC, at a different orientation to other structures in the complex. Its steps are aligned perpendicular to the rising of Capella at that time, so that a person looking out a doorway on the building would have faced it directly. Capella is significant as its heliacal rising took place within a day of the Sun passing directly overhead over Monte Albán.[41]

Multiple status edit

Professor William Wallace Campbell of the Lick Observatory announced that Capella was binary in 1899, based on spectroscopic observations—he noted on photographic plates taken from August 1896 to February 1897 that a second spectrum appeared superimposed over the first, and that there was a doppler shift to violet in September and October and to red in November and February—showing that the components were moving toward and away from the Earth (and hence orbiting each other).[42][43] Almost simultaneously, British astronomer Hugh Newall had observed its composite spectrum with a four prism spectroscope attached to a 25-inch (64 cm) telescope at Cambridge in July 1899, concluding that it was a binary star system.[44]

Many observers tried to discern the component stars without success.[45] Known as "The Interferometrist's Friend", it was first resolved interferometrically in 1919 by John Anderson and Francis Pease at Mount Wilson Observatory, who published an orbit in 1920 based on their observations.[46][47] This was the first interferometric measurement of any object outside the Solar System.[48] A high-precision orbit was published in 1994 based on observations by the Mark III Stellar Interferometer, again at Mount Wilson Observatory.[49] Capella also became the first astronomical object to be imaged by a separate element optical interferometer when it was imaged by the Cambridge Optical Aperture Synthesis Telescope in September 1995.[50]

In 1914, Finnish astronomer Ragnar Furuhjelm observed that the spectroscopic binary had a faint companion star, which, as its proper motion was similar to that of the spectroscopic binary, was probably physically bound to it.[51] In February 1936, Carl L. Stearns observed that this companion appeared to be double itself;[52] this was confirmed in September that year by Gerard Kuiper. This pair are designated Capella H and L.[53]

X-ray source edit

Two Aerobee-Hi rocket flights on September 20, 1962, and March 15, 1963, detected and confirmed an X-ray source in Auriga at RA 05h 09m Dec +45°, identified as Capella.[54] A major milestone in stellar X-ray astronomy happened on April 5, 1974, with the detection of the strongest emission of X-rays up to that time[55] from Capella, measured at more than 10,000 times the x-ray luminosity of the Sun.[56] A rocket flight on that date briefly calibrated its attitude control system when a star sensor pointed the payload axis at Capella. During this period, X-rays in the range 0.2–1.6 keV were detected by an X-ray reflector system co-aligned with the star sensor.[56]

The X-ray luminosity (Lx) of ~1024 W (1031 erg s−1) is four orders of magnitude above the Sun's X-ray luminosity.[56] Capella's X-rays are thought to be primarily from the corona of the most massive star.[57] Capella is ROSAT X-ray source 1RXS J051642.2+460001. The high temperature of Capella's corona as obtained from the first coronal X-ray spectrum of Capella using HEAO 1 would require magnetic confinement, unless it is a free-flowing coronal wind.[58]

Observation edit

 
Annotated night sky image showing Auriga and the Pleiades—Capella is the brightest star, towards top left

With an average apparent magnitude of +0.08, Capella is the brightest object in the constellation Auriga, the sixth-brightest star in the night sky, the third-brightest in the northern celestial hemisphere (after Arcturus and Vega), and the fourth-brightest visible to the naked eye from the latitude 40°N. It appears to be a rich yellowish-white colour, although the yellow colour is more apparent during daylight observation with a telescope, due to the contrast against the blue sky.[59]

Capella is closer to the north celestial pole than any other first-magnitude star.[60][note 3] Its northern declination is such that it is actually invisible south of latitude 44°S—this includes southernmost New Zealand, Argentina and Chile as well as the Falkland Islands. Conversely it is circumpolar north of 44°N: for the whole of the United Kingdom and Canada (except for part of Southern Ontario), most of Europe, and the northernmost fringes of the contiguous United States, the star never sets. Capella and Vega are on opposite sides of the pole, at about the same distance from it, such that an imaginary line between the two stars will nearly pass through Polaris.[61] Visible halfway between Orion's Belt and Polaris, Capella is at its highest in the night sky at midnight in early December and is regarded as a prominent star of the northern winter sky.[62]

A few degrees to the southwest of Capella lie three stars, Epsilon Aurigae, Zeta Aurigae and Eta Aurigae, the latter two of which are known as "The Kids", or Haedi. The four form a familiar pattern, or asterism, in the sky.[63]

Distance edit

Based on an annual parallax shift of 76.20 milliarcseconds (with a margin of error of 0.46 milliarcseconds) as measured by the Hipparcos satellite, this system is estimated to be 42.8 light-years (13.12 parsecs) from Earth, with a margin of error of 0.3 light-year (0.09 parsec).[2] An alternative method to determine the distance is via the orbital parallax, which gives a distance of 42.92 light-years (13.159 parsecs) with a margin of error of only 0.1%.[12] Capella is estimated to have been a little closer to the Solar System in the past, passing within 29 light-years distant around 237,000 years ago.[64] At this range, it would have shone at apparent magnitude −0.82, comparable to Canopus today.[65]

In a 1960 paper, American astronomer Olin J. Eggen concluded that Capella was a member of the Hyades moving group, a group of stars moving in the same direction as the Hyades cluster, after analysing its proper motion and parallax. Members of the group are of a similar age, and those that are around 2.5 times as massive as the Sun have moved off the main sequence after exhausting their core hydrogen reserves and are expanding and cooling into red giants.[3][66]

Stellar system edit

 
Capella components compared with the Sun

There are several stars within a few arcminutes of Capella and some have been listed as companions in various multiple star catalogues. The Washington Double Star Catalog lists components A, B, C, D, E, F, G, H, I, L, M, N, O, P, Q, and R, with A being the naked-eye star. Most are only line-of-sight companions,[67] but the close pair of red dwarfs H and L are at the same distance as the bright component A and moving through space along with it.[68] Capella A is itself a spectroscopic binary with components Aa and Ab, both giant stars. The pair of giants is separated from the pair of red dwarfs by 723".[12]

American astronomer Robert Burnham Jr. described a scale model of the system where Capella A was represented by spheres 13 and 7 inches across, separated by ten feet. The red dwarfs were then each 0.7 inch across and they were separated by 420 feet. At this scale, the two pairs are 21 miles apart.[69]

Capella A edit

 
Hertzsprung–Russell diagram showing an evolutionary track for a star of approximately the mass of the two Capella giants. The current states of Capella Aa and Ab are marked.[12]

Capella A consists of two yellow evolved stars that have been calculated to orbit each other every 104.02128 ± 0.00016 days, with a semimajor axis of 111.11 ± 0.10 million km (0.74272 ± 0.00069 AU), roughly the distance between Venus and the Sun. The pair is not an eclipsing binary—that is, as seen from Earth, neither star passes in front of the other. The orbit is known extremely accurately and can be used to derive an orbital parallax with far better precision than the one measured directly. The stars are not near enough to each other for the Roche lobe of either star to have been filled and any significant mass transfer to have taken place, even during the red giant stage of the primary star.[12]

Modern convention designates the more luminous cooler star as component Aa and its spectral type has been usually measured between G2 and K0. The hotter secondary Ab has been given various spectral types of late (cooler) F or early (warmer) G. The MK spectral types of the two stars have been measured a number of times, and they are both consistently assigned a luminosity class of III indicating a giant star.[70] The composite spectrum appears to be dominated by the primary star due to its sharper absorption lines; the lines from the secondary are broadened and blurred by its rapid rotation.[45] The composite spectral class is given as approximately G3III, but with a specific mention of features due to a cooler component.[9] The most recent specific published types are K0III and G1III,[13] although older values are still widely quoted such as G5IIIe + G0III from the Bright Star Catalogue[3] or G8III + G0III by Eggen.[66] Where the context is clear, these two components have been referred to as A and B.[71]

The individual apparent magnitudes of the two component stars cannot be directly measured, but their relative brightness has been measured at various wavelengths. They have very nearly equal brightness in the visible light spectrum, with the hotter secondary component generally being found to be a few tenths of a magnitude brighter.[12] A 2016 measurement gives the magnitude difference between the two stars at a wavelength of 700 nm as 0.00 ± 0.1.[72]

The physical properties of the two stars can be determined with high accuracy. The masses are derived directly from the orbital solution, with Aa being 2.5687 ± 0.0074 M and Ab being 2.4828 ± 0.0067 M. Their angular radii have been directly measured; in combination with the very accurate distance, this gives 11.98 ± 0.57 R and 8.83 ± 0.33 R for Aa and Ab, respectively. Their surface temperatures can be calculated by comparison of observed and synthetic spectra, direct measurement of their angular diameters and brightnesses, calibration against their observed colour indices, and disentangling of high resolution spectra. Weighted averages of these four methods give 4,970 ± 50 K for Aa and 5,730 ± 60 for Ab. Their bolometric luminosities are most accurately derived from their apparent magnitudes and bolometric corrections, but are confirmed by calculation from the temperatures and radii of the stars. Aa is 78.7 ± 4.2 times as luminous as the Sun and Ab 72.7 ± 3.6 times as luminous, so the star defined as the primary component is the more luminous when all wavelengths are considered but very slightly less bright at visual wavelengths.[12]

Estimated to be 590 to 650 million years old,[12] the stars were probably at the hot end of spectral class A during their main-sequence lifetime, similar to Vega. They have now exhausted their core hydrogen and evolved off the main sequence, their outer layers expanding and cooling.[73] Despite the giant luminosity class, the secondary component is very clearly within the Hertzsprung gap on the Hertzsprung–Russell diagram, still expanding and cooling towards the red giant branch, making it a subgiant in evolutionary terms. The more massive primary has already passed through this stage, when it reached a maximum radius of 36 to 38 times that of the Sun. It is now a red clump star which is fusing helium to carbon and oxygen in its core, a process that has not yet begun for the less massive star. Detailed analysis shows that it is nearing the end of this stage and starting to expand again which will lead it to the asymptotic giant branch. Isotope abundances[note 4] and spin rates confirm this evolutionary difference between the two stars. Heavy element abundances are broadly comparable to those of the Sun and the overall metallicity is slightly less than the Sun's.[45]

The rotational period of each star can be measured by observing periodic variations in the doppler shifts of their spectral lines. The absolute rotational velocities of the two stars are known from their inclinations, rotation periods, and sizes, but the projected equatorial rotational velocities measured using doppler broadening of spectral lines are a standard measure and these are generally quoted.[45] Capella Aa has a projected rotational velocity of 4.1 ± 0.4 km per second, taking 104 ± 3 days to complete one rotation, while Capella Ab spins much more rapidly at 35.0 ± 0.5 km per second, completing a full rotation in only 8.5 ± 0.2 days. Rotational braking occurs in all stars when they expand into giants, and binary stars are also tidally braked. Capella Aa has slowed until it is rotationally locked to the orbital period, although theory predicts that it should still be rotating more quickly from a starting point of a rapidly-spinning main sequence A star.[12]

Capella has long been suspected to be slightly variable. Its amplitude of about 0.1 magnitudes means that it may at times be brighter or fainter than Rigel, Betelgeuse and Vega, which are also variable. The system has been classified as an RS Canum Venaticorum variable,[10] a class of binary stars with active chromospheres that cause huge starspots, but it is still only listed as a suspected variable in the General Catalogue of Variable Stars.[11] Unusually for RS CVn systems, the hotter star, Capella Ab, has the more active atmosphere because it is located in the Hertzsprung gap—a stage where it is changing its angular momentum and deepening its convection zone.[71]

The active atmospheres and closeness of these stars means that they are among the brightest X-ray sources in the sky. However the X-ray emission is due to stable coronal structures and not eruptive flaring activity. Coronal loops larger than the Sun and with temperatures of several million kelvin are likely to be responsible for the majority of the X-rays.[74]

Capella HL edit

The seventh companion published for Capella, component H, is physically associated with the bright primary star. It is a red dwarf separated from the pair of G-type giants by a distance of around 10,000 AU.[68] It has its own close companion, an even fainter red dwarf that was 1.8″ away when it was discovered in 1935. It is component L in double star catalogues. In 2015 the separation had increased to 3.5″, which was sufficient to allow tentative orbital parameters to be derived, 80 years after its discovery.[12][75] The Gliese-Jahreiss Catalogue of nearby stars designates the binary system as GJ 195. The two components are then referred to individually as GJ 195 A and B.[16]

The two stars are reported to have a 3.5-visual-magnitude difference (2.3 mag in the passband of the Gaia spacecraft) although the difference is much smaller at infrared wavelengths. This is unexpected and may indicate further unseen companions.[12]

The mass of the stars can, in principle, be determined from the orbital motion, but uncertainties in the orbit have led to widely varying results. In 1975, an eccentric 388-year orbit gave masses of 0.65 M and 0.13 M.[75] A smaller near-circular orbit published in 2015 had a 300-year orbit, benefitting from mass constraints of 0.57 M and 0.53 M, respectively, for GJ 195 A and B, based on their infrared magnitudes.[12]

Visual companions edit

Six visual companions to Capella were discovered before Capella H and are generally known only as Capella B through G. None are thought to be physically associated with Capella, although all appear closer in the sky than the HL pair.[69]

Multiple/double star designation: WDS 05167+4600[27]
Component Primary Right
ascension
(α)
Equinox J2000.0
Declination (δ)
Equinox J2000.0
Epoch of
observed
separation
Angular
distance
from
primary
Position
angle
(relative
to primary)
Apparent
magnitude
(V)
Database
reference
B A 05h 16m 42.7s+46° 00′ 55″ 1898 46.6 23° 17.1
C A 05h 16m 35.9s+46° 01′ 12″ 1878 78.2 318° 15.1
D A 05h 16m 40.1s+45° 58′ 07″ 1878 126.2 183° 13.6
E A 05h 16.5m +46° 02′ 1908 154.1 319° 12.1
F A 05h 16m 48.748s+45° 58′ 30.84″ 1999 112.0 137° 10.21 SIMBAD
G A 05h 16m 31.852s+46° 08′ 27.42″ 2003 522.4 349° 8.10 SIMBAD

Component F is also known as TYC  3358-3142-1. It is listed with a spectral type of K[76] although it is included in a catalogue of OB stars as a distant luminous star.[77]

Component G is BD+45 1076, with a spectral type of F0,[76] at a distance of 401 light-years (123 parsecs).[78] It is identified as a variable member of the Guide Star Catalogue from Chandra observations although it is not known what type of variability.[79] It is known to be an X-ray source with an active corona.[78]

Several other stars have also been catalogued as companions to Capella.[27] Components I, Q and R are 13th-magnitude stars at distances of 92″, 133″ and 134″.[80] V538 Aurigae and its close companion HD 233153 are red dwarfs ten degrees away from Capella; they have very similar space motions but the small difference makes it possible that this is just a coincidence.[81] Two faint stars have been discovered by speckle imaging in the Capella HL field, around 10″ distant from that pair. These have been catalogued as Capella O and P. It is not known whether they are physically associated with the red dwarf binary.[82]

Etymology and culture edit

Capella traditionally marks the left shoulder of the constellation's eponymous charioteer, or, according to the 2nd-century astronomer Ptolemy's Almagest, the goat that the charioteer is carrying. In Bayer's 1603 work Uranometria, Capella marks the charioteer's back.[83] The three Haedi had been identified as a separate constellation by Pliny the Elder and Manilius, and were called Capra, Caper, or Hircus, all of which relate to its status as the "goat star".[40] Ptolemy merged the Charioteer and the Goats in the 2nd-century Almagest.[84]

In Greek mythology, the star represented the goat Amalthea that suckled Zeus. It was this goat whose horn, after accidentally being broken off by Zeus, was transformed into the Cornucopia, or "horn of plenty", which would be filled with whatever its owner desired.[37] Though most often associated with Amalthea, Capella has sometimes been associated with Amalthea's owner, a nymph. The myth of the nymph says that the goat's hideous appearance, resembling a Gorgon, was partially responsible for the Titans' defeat, after Zeus skinned the goat and wore it as his aegis.[85]

In medieval accounts, it bore the uncommon name Alhajoth (also spelled Alhaior, Althaiot, Alhaiset, Alhatod, Alhojet, Alanac, Alanat, Alioc), which (especially the last) may be a corruption of its Arabic name, العيوق, al-cayyūq.[86] cAyyūq has no clear significance in Arabic,[87] but may be an Arabized form of the Greek αίξ aiks "goat"; cf. the modern Greek Αίγα Aiga, the feminine of goat.[86] To the Bedouin of the Negev and Sinai, Capella al-'Ayyūq ath-Thurayyā "Capella of the Pleiades", from its role as pointing out the position of that asterism.[88] Another name in Arabic was Al-Rākib "the driver", a translation of the Greek.[86]

To the ancient Balts, Capella was known as Perkūno Ožka "Thunder's Goat", or Tikutis.[89] Conversely in Slavic Macedonian folklore, Capella was Jastreb "the hawk", flying high above and ready to pounce on Mother Hen (the Pleiades) and the Rooster (Nath).[90]

Astrologically, Capella portends civic and military honors and wealth.[39] In the Middle Ages, it was considered a Behenian fixed star, with the stone sapphire and the plants horehound, mint, mugwort and mandrake as attributes. Cornelius Agrippa listed its kabbalistic sign   with the name Hircus (Latin for goat).[91][92]

In Hindu mythology, Capella was seen as the heart of Brahma, Brahma Hṛdaya.[39] In traditional Chinese astronomy, Capella was part of the asterism 五車 (Wŭ chē; English: Five Chariots), which consisted of Capella together with Beta Aurigae, Theta Aurigae and Iota Aurigae, as well as Beta Tauri.[93][94] Since it was the second star in this asterism, it has the Chinese name 五車二 (Wŭ chē èr; English: Second of the Five Chariots).[95]

In Quechua it was known as Colça;[39] the Incas held the star in high regard.[96] The Hawaiians saw Capella as part of an asterism Ke ka o Makali'i ("The canoe bailer of Makali'i") that helped them navigate at sea. Called Hoku-lei "star wreath", it formed this asterism with Procyon, Sirius, Castor and Pollux.[26] In Tahitian folklore, Capella was Tahi-ari'i, the wife of Fa'a-nui (Auriga) and mother of prince Ta'urua (Venus) who sails his canoe across the sky.[97] In Inuit astronomy, Capella, along with Menkalinan (Beta Aurigae), Pollux (Beta Geminorum) and Castor (Alpha Geminorum), formed a constellation Quturjuuk, "collar-bones", the two pairs of stars denoting a bone each. Used for navigation and time-keeping at night, the constellation was recognised from Alaska to western Greenland.[98] The Gwich'in saw Capella and Menkalinan has forming shreets'ą įį vidzee, the right ear of the large circumpolar constellation Yahdii, which covered much of the night sky, and whose orientation facilitated navigation and timekeeping.[99]

In Australian Aboriginal mythology for the Boorong people of Victoria, Capella was Purra, the kangaroo, pursued and killed by the nearby Gemini twins, Yurree (Castor) and Wanjel (Pollux).[100] The Wardaman people of northern Australia knew the star as Yagalal, a ceremonial fish scale, related to Guwamba the barramundi (Aldebaran).[101]

Namesakes edit

See also edit

Notes edit

  1. ^ a b Pertains to the center of mass of the Capella Aa/Ab binary system. See Volume 1, The Hipparcos and Tycho Catalogues 2018-09-01 at the Wayback Machine, European Space Agency, 1997, §2.3.4, and the entry 2016-03-03 at the Wayback Machine in the Hipparcos catalogue (CDS ID I/239 2016-03-03 at the Wayback Machine.)
  2. ^ the distance between the Earth and the Sun is one astronomical unit
  3. ^ Polaris is only second magnitude.
  4. ^ The lithium abundance, C12/C13 ratio and C/N ratio have all declined in Capella Aa but not in Capella Ab.

References edit

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Sources edit


capella, other, uses, disambiguation, brightest, star, northern, constellation, auriga, bayer, designation, aurigae, which, latinised, alpha, aurigae, abbreviated, alpha, sixth, brightest, star, night, third, brightest, northern, celestial, hemisphere, after, . For other uses see Capella disambiguation Capella is the brightest star in the northern constellation of Auriga It has the Bayer designation a Aurigae which is Latinised to Alpha Aurigae and abbreviated Alpha Aur or a Aur Capella is the sixth brightest star in the night sky and the third brightest in the northern celestial hemisphere after Arcturus and Vega A prominent object in the northern winter sky it is circumpolar to observers north of 44 N Its name meaning little goat in Latin Capella depicted the goat Amalthea that suckled Zeus in classical mythology Capella is relatively close at 42 9 light years 13 2 pc from the Sun It is one of the brightest X ray sources in the sky thought to come primarily from the corona of Capella Aa CapellaLocation of Capella Aa as the brightest star circled Observation dataEpoch J2000 0 Equinox J2000 0 ICRS Constellation Auriga Pronunciation k e ˈ p ɛ l e 1 A Right ascension 05h 16m 41 35871s 2 note 1 Declination 45 59 52 7693 2 note 1 Apparent magnitude V 0 08 3 0 03 0 16 4 H Right ascension 05h 17m 23 728s 5 Declination 45 50 22 97 5 Apparent magnitude V 10 16 6 L Right ascension 05h 17m 23 943s 7 Declination 45 50 19 84 7 Apparent magnitude V 13 7 8 Characteristics A Spectral type G3III 9 U B color index 0 44 3 B V color index 0 80 3 V R color index 0 3 3 R I color index 0 44 3 Variable type RS CVn 10 suspected 11 Aa Evolutionary stage Red clump 12 Spectral type K0III 13 Ab Evolutionary stage Subgiant 12 Spectral type G1III 13 H Evolutionary stage Main sequence red dwarf 14 Spectral type M2 5 V 15 U B color index 1 24 16 B V color index 1 50 14 R I color index 0 91 14 L Evolutionary stage Main sequence red dwarf Spectral type M4 17 AstrometryARadial velocity Rv 29 9387 0 0032 12 km sProper motion m RA 75 52 2 mas yr Dec 427 11 2 mas yrParallax p 76 20 0 46 mas 2 Distance42 919 0 049 ly 13 159 0 015 12 pc AaAbsolute magnitude MV 0 296 12 AbAbsolute magnitude MV 0 167 12 HLRadial velocity Rv 31 63 0 14 12 km s HProper motion m RA 88 57 18 mas yr Dec 428 91 18 mas yrParallax p 74 9521 0 0188 mas 19 Distance43 52 0 01 ly 13 342 0 003 pc Absolute magnitude MV 9 53 20 LProper motion m RA 54 1 21 mas yr Dec 417 5 21 mas yrParallax p 75 1838 0 0534 mas 22 Distance43 38 0 03 ly 13 301 0 009 pc Absolute magnitude MV 13 1 23 Orbit 12 PrimaryAaCompanionAbPeriod P 104 02128 0 00016 dSemi major axis a 0 056442 0 000023 0 74272 0 00069 AU Eccentricity e 0 00089 0 00011Inclination i 137 156 0 046 Longitude of the node W 40 522 0 039 Periastron epoch T 2 448 147 6 2 6 JDArgument of periastron w primary 342 6 9 0 JD Semi amplitude K1 primary 25 9611 0 0044 km sSemi amplitude K2 secondary 26 860 0 0017 km s Orbit 12 PrimaryHCompanionLPeriod P 300 yrSemi major axis a 3 5 40 AU 24 Eccentricity e 0 75Inclination i 52 Longitude of the node W 288 Periastron epoch T 2 220Argument of periastron w secondary 88 Details 12 AMetallicity Fe H 0 04 0 06 dexAge590 650 Myr AaMass2 5687 0 0074 M Radius11 98 0 57 R Luminosity bolometric 78 7 4 2 L Surface gravity log g 2 691 0 041 cgsTemperature4 970 50 KRotation104 3 daysRotational velocity v sin i 4 1 0 4 km sAbMass2 4828 0 0067 M Radius8 83 0 33 R Luminosity bolometric 72 7 3 6 L Surface gravity log g 2 941 0 032 cgsTemperature5 730 60 KRotation8 5 0 2 daysRotational velocity v sin i 35 0 0 5 km s HMass0 57 12 24 M Radius0 54 0 03 20 R Luminosity bolometric 0 05 20 L Surface gravity log g 4 75 0 05 cgsTemperature3 700 150 20 KMetallicity Fe H 0 1 20 dexLMass0 53 12 M Other designationsAlhajoth Hokulei a Aurigae 13 Aurigae BD 45 1077 FK5 193 GC 6427 HD 34029 HIP 24608 HR 1708 SAO 40186 PPM 47925 ADS 3841 CCDM J05168 4559 WDS 05167 4600 LTT 11619 NLTT 14766 25 3 26 27 16 A GJ 194HL GJ 195 16 H PPM 47938 G 96 29 LTT 11622 NLTT 14788 2MASS J05172386 4550229 28 L 2MASS J05172394 4550198 29 Database referencesSIMBADCapellaCapella HCapella L Although it appears to be a single star to the naked eye Capella is actually a quadruple star system organized in two binary pairs made up of the stars Capella Aa Capella Ab Capella H and Capella L The primary pair Capella Aa and Capella Ab are two bright yellow giant stars both of which are around 2 5 times as massive as the Sun The secondary pair Capella H and Capella L are around 10 000 astronomical units AU note 2 from the first and are two faint small and relatively cool red dwarfs Capella Aa and Capella Ab have exhausted their core hydrogen and cooled and expanded moving off the main sequence They are in a very tight circular orbit about 0 74 AU apart and orbit each other every 104 days Capella Aa is the cooler and more luminous of the two with spectral class K0III it is 78 7 4 2 times the Sun s luminosity and 11 98 0 57 times its radius An aging red clump star it is fusing helium to carbon and oxygen in its core Capella Ab is slightly smaller and hotter and of spectral class G1III it is 72 7 3 6 times as luminous as the Sun and 8 83 0 33 times its radius It is in the Hertzsprung gap corresponding to a brief subgiant evolutionary phase as it expands and cools to become a red giant Several other stars in the same visual field have been catalogued as companions but are physically unrelated Contents 1 Nomenclature 2 Observational history 2 1 Multiple status 2 2 X ray source 3 Observation 4 Distance 5 Stellar system 5 1 Capella A 5 2 Capella HL 5 3 Visual companions 6 Etymology and culture 6 1 Namesakes 7 See also 8 Notes 9 References 10 SourcesNomenclature edit nbsp Capella is the brightest star in the constellation of Auriga upper left a Aurigae Latinised to Alpha Aurigae is the star system s Bayer designation It also has the Flamsteed designation 13 Aurigae It is listed in several multiple star catalogues as ADS 3841 CCDM J05168 4559 and WDS J05167 4600 As a relatively nearby star system Capella is listed in the Gliese Jahreiss Catalogue with designations GJ 194 for the bright pair of giants and GJ 195 for the faint pair of red dwarfs The traditional name Capella is Latin for small female goat the alternative name Capra was more commonly used in classical times 30 It is the translation of the Greek star name Aἴ3 aix meaning the Goat As the sound of the Greek term for the goat aἴ3 is similar to the sound of the name for the Aegaean Sea this star has been used for weather rules and determining the seasonal wind direction 31 In 2016 the International Astronomical Union organized a Working Group on Star Names WGSN 32 to catalogue and standardize proper names for stars The WGSN s first bulletin of July 2016 33 included a table of the first two batches of names approved by the WGSN which included Capella for this star It is now so entered in the IAU Catalog of Star Names 34 The catalogue of star names lists Capella as applying to the star a Aurigae Aa 35 Observational history editCapella was the brightest star in the night sky from 210 000 years ago to 160 000 years ago at about 1 8 in apparent magnitude At 1 1 Aldebaran was brightest before this period it and Capella were situated rather close to each other in the sky and approximated boreal pole stars at the time 36 nbsp Building J foreground at Monte Alban Capella is thought to be mentioned in an Akkadian inscription dating to the 20th century BC 37 Its goat associated symbolism dates back to Mesopotamia as a constellation called GAM Gamlum or MUL GAM in the 7th century BC document MUL APIN GAM represented a scimitar or crook and may have represented the star alone or the constellation of Auriga as a whole Later Bedouin astronomers created constellations that were groups of animals where each star represented one animal The stars of Auriga comprised a herd of goats an association also present in Greek mythology 38 It is sometimes called the Shepherd s Star in English literature 39 Capella was seen as a portent of rain in classical times 40 Building J of the pre Columbian site Monte Alban in Oaxaca state in Mexico was built around 275 BC at a different orientation to other structures in the complex Its steps are aligned perpendicular to the rising of Capella at that time so that a person looking out a doorway on the building would have faced it directly Capella is significant as its heliacal rising took place within a day of the Sun passing directly overhead over Monte Alban 41 Multiple status edit Professor William Wallace Campbell of the Lick Observatory announced that Capella was binary in 1899 based on spectroscopic observations he noted on photographic plates taken from August 1896 to February 1897 that a second spectrum appeared superimposed over the first and that there was a doppler shift to violet in September and October and to red in November and February showing that the components were moving toward and away from the Earth and hence orbiting each other 42 43 Almost simultaneously British astronomer Hugh Newall had observed its composite spectrum with a four prism spectroscope attached to a 25 inch 64 cm telescope at Cambridge in July 1899 concluding that it was a binary star system 44 Many observers tried to discern the component stars without success 45 Known as The Interferometrist s Friend it was first resolved interferometrically in 1919 by John Anderson and Francis Pease at Mount Wilson Observatory who published an orbit in 1920 based on their observations 46 47 This was the first interferometric measurement of any object outside the Solar System 48 A high precision orbit was published in 1994 based on observations by the Mark III Stellar Interferometer again at Mount Wilson Observatory 49 Capella also became the first astronomical object to be imaged by a separate element optical interferometer when it was imaged by the Cambridge Optical Aperture Synthesis Telescope in September 1995 50 In 1914 Finnish astronomer Ragnar Furuhjelm observed that the spectroscopic binary had a faint companion star which as its proper motion was similar to that of the spectroscopic binary was probably physically bound to it 51 In February 1936 Carl L Stearns observed that this companion appeared to be double itself 52 this was confirmed in September that year by Gerard Kuiper This pair are designated Capella H and L 53 X ray source edit Two Aerobee Hi rocket flights on September 20 1962 and March 15 1963 detected and confirmed an X ray source in Auriga at RA 05h 09m Dec 45 identified as Capella 54 A major milestone in stellar X ray astronomy happened on April 5 1974 with the detection of the strongest emission of X rays up to that time 55 from Capella measured at more than 10 000 times the x ray luminosity of the Sun 56 A rocket flight on that date briefly calibrated its attitude control system when a star sensor pointed the payload axis at Capella During this period X rays in the range 0 2 1 6 keV were detected by an X ray reflector system co aligned with the star sensor 56 The X ray luminosity Lx of 1024 W 1031 erg s 1 is four orders of magnitude above the Sun s X ray luminosity 56 Capella s X rays are thought to be primarily from the corona of the most massive star 57 Capella is ROSAT X ray source 1RXS J051642 2 460001 The high temperature of Capella s corona as obtained from the first coronal X ray spectrum of Capella using HEAO 1 would require magnetic confinement unless it is a free flowing coronal wind 58 Observation edit nbsp Annotated night sky image showing Auriga and the Pleiades Capella is the brightest star towards top left With an average apparent magnitude of 0 08 Capella is the brightest object in the constellation Auriga the sixth brightest star in the night sky the third brightest in the northern celestial hemisphere after Arcturus and Vega and the fourth brightest visible to the naked eye from the latitude 40 N It appears to be a rich yellowish white colour although the yellow colour is more apparent during daylight observation with a telescope due to the contrast against the blue sky 59 Capella is closer to the north celestial pole than any other first magnitude star 60 note 3 Its northern declination is such that it is actually invisible south of latitude 44 S this includes southernmost New Zealand Argentina and Chile as well as the Falkland Islands Conversely it is circumpolar north of 44 N for the whole of the United Kingdom and Canada except for part of Southern Ontario most of Europe and the northernmost fringes of the contiguous United States the star never sets Capella and Vega are on opposite sides of the pole at about the same distance from it such that an imaginary line between the two stars will nearly pass through Polaris 61 Visible halfway between Orion s Belt and Polaris Capella is at its highest in the night sky at midnight in early December and is regarded as a prominent star of the northern winter sky 62 A few degrees to the southwest of Capella lie three stars Epsilon Aurigae Zeta Aurigae and Eta Aurigae the latter two of which are known as The Kids or Haedi The four form a familiar pattern or asterism in the sky 63 Distance editBased on an annual parallax shift of 76 20 milliarcseconds with a margin of error of 0 46 milliarcseconds as measured by the Hipparcos satellite this system is estimated to be 42 8 light years 13 12 parsecs from Earth with a margin of error of 0 3 light year 0 09 parsec 2 An alternative method to determine the distance is via the orbital parallax which gives a distance of 42 92 light years 13 159 parsecs with a margin of error of only 0 1 12 Capella is estimated to have been a little closer to the Solar System in the past passing within 29 light years distant around 237 000 years ago 64 At this range it would have shone at apparent magnitude 0 82 comparable to Canopus today 65 In a 1960 paper American astronomer Olin J Eggen concluded that Capella was a member of the Hyades moving group a group of stars moving in the same direction as the Hyades cluster after analysing its proper motion and parallax Members of the group are of a similar age and those that are around 2 5 times as massive as the Sun have moved off the main sequence after exhausting their core hydrogen reserves and are expanding and cooling into red giants 3 66 Stellar system edit nbsp Capella components compared with the Sun There are several stars within a few arcminutes of Capella and some have been listed as companions in various multiple star catalogues The Washington Double Star Catalog lists components A B C D E F G H I L M N O P Q and R with A being the naked eye star Most are only line of sight companions 67 but the close pair of red dwarfs H and L are at the same distance as the bright component A and moving through space along with it 68 Capella A is itself a spectroscopic binary with components Aa and Ab both giant stars The pair of giants is separated from the pair of red dwarfs by 723 12 American astronomer Robert Burnham Jr described a scale model of the system where Capella A was represented by spheres 13 and 7 inches across separated by ten feet The red dwarfs were then each 0 7 inch across and they were separated by 420 feet At this scale the two pairs are 21 miles apart 69 Capella A edit nbsp Hertzsprung Russell diagram showing an evolutionary track for a star of approximately the mass of the two Capella giants The current states of Capella Aa and Ab are marked 12 Capella A consists of two yellow evolved stars that have been calculated to orbit each other every 104 02128 0 00016 days with a semimajor axis of 111 11 0 10 million km 0 74272 0 00069 AU roughly the distance between Venus and the Sun The pair is not an eclipsing binary that is as seen from Earth neither star passes in front of the other The orbit is known extremely accurately and can be used to derive an orbital parallax with far better precision than the one measured directly The stars are not near enough to each other for the Roche lobe of either star to have been filled and any significant mass transfer to have taken place even during the red giant stage of the primary star 12 Modern convention designates the more luminous cooler star as component Aa and its spectral type has been usually measured between G2 and K0 The hotter secondary Ab has been given various spectral types of late cooler F or early warmer G The MK spectral types of the two stars have been measured a number of times and they are both consistently assigned a luminosity class of III indicating a giant star 70 The composite spectrum appears to be dominated by the primary star due to its sharper absorption lines the lines from the secondary are broadened and blurred by its rapid rotation 45 The composite spectral class is given as approximately G3III but with a specific mention of features due to a cooler component 9 The most recent specific published types are K0III and G1III 13 although older values are still widely quoted such as G5IIIe G0III from the Bright Star Catalogue 3 or G8III G0III by Eggen 66 Where the context is clear these two components have been referred to as A and B 71 The individual apparent magnitudes of the two component stars cannot be directly measured but their relative brightness has been measured at various wavelengths They have very nearly equal brightness in the visible light spectrum with the hotter secondary component generally being found to be a few tenths of a magnitude brighter 12 A 2016 measurement gives the magnitude difference between the two stars at a wavelength of 700 nm as 0 00 0 1 72 The physical properties of the two stars can be determined with high accuracy The masses are derived directly from the orbital solution with Aa being 2 5687 0 0074 M and Ab being 2 4828 0 0067 M Their angular radii have been directly measured in combination with the very accurate distance this gives 11 98 0 57 R and 8 83 0 33 R for Aa and Ab respectively Their surface temperatures can be calculated by comparison of observed and synthetic spectra direct measurement of their angular diameters and brightnesses calibration against their observed colour indices and disentangling of high resolution spectra Weighted averages of these four methods give 4 970 50 K for Aa and 5 730 60 for Ab Their bolometric luminosities are most accurately derived from their apparent magnitudes and bolometric corrections but are confirmed by calculation from the temperatures and radii of the stars Aa is 78 7 4 2 times as luminous as the Sun and Ab 72 7 3 6 times as luminous so the star defined as the primary component is the more luminous when all wavelengths are considered but very slightly less bright at visual wavelengths 12 Estimated to be 590 to 650 million years old 12 the stars were probably at the hot end of spectral class A during their main sequence lifetime similar to Vega They have now exhausted their core hydrogen and evolved off the main sequence their outer layers expanding and cooling 73 Despite the giant luminosity class the secondary component is very clearly within the Hertzsprung gap on the Hertzsprung Russell diagram still expanding and cooling towards the red giant branch making it a subgiant in evolutionary terms The more massive primary has already passed through this stage when it reached a maximum radius of 36 to 38 times that of the Sun It is now a red clump star which is fusing helium to carbon and oxygen in its core a process that has not yet begun for the less massive star Detailed analysis shows that it is nearing the end of this stage and starting to expand again which will lead it to the asymptotic giant branch Isotope abundances note 4 and spin rates confirm this evolutionary difference between the two stars Heavy element abundances are broadly comparable to those of the Sun and the overall metallicity is slightly less than the Sun s 45 The rotational period of each star can be measured by observing periodic variations in the doppler shifts of their spectral lines The absolute rotational velocities of the two stars are known from their inclinations rotation periods and sizes but the projected equatorial rotational velocities measured using doppler broadening of spectral lines are a standard measure and these are generally quoted 45 Capella Aa has a projected rotational velocity of 4 1 0 4 km per second taking 104 3 days to complete one rotation while Capella Ab spins much more rapidly at 35 0 0 5 km per second completing a full rotation in only 8 5 0 2 days Rotational braking occurs in all stars when they expand into giants and binary stars are also tidally braked Capella Aa has slowed until it is rotationally locked to the orbital period although theory predicts that it should still be rotating more quickly from a starting point of a rapidly spinning main sequence A star 12 Capella has long been suspected to be slightly variable Its amplitude of about 0 1 magnitudes means that it may at times be brighter or fainter than Rigel Betelgeuse and Vega which are also variable The system has been classified as an RS Canum Venaticorum variable 10 a class of binary stars with active chromospheres that cause huge starspots but it is still only listed as a suspected variable in the General Catalogue of Variable Stars 11 Unusually for RS CVn systems the hotter star Capella Ab has the more active atmosphere because it is located in the Hertzsprung gap a stage where it is changing its angular momentum and deepening its convection zone 71 The active atmospheres and closeness of these stars means that they are among the brightest X ray sources in the sky However the X ray emission is due to stable coronal structures and not eruptive flaring activity Coronal loops larger than the Sun and with temperatures of several million kelvin are likely to be responsible for the majority of the X rays 74 Capella HL edit The seventh companion published for Capella component H is physically associated with the bright primary star It is a red dwarf separated from the pair of G type giants by a distance of around 10 000 AU 68 It has its own close companion an even fainter red dwarf that was 1 8 away when it was discovered in 1935 It is component L in double star catalogues In 2015 the separation had increased to 3 5 which was sufficient to allow tentative orbital parameters to be derived 80 years after its discovery 12 75 The Gliese Jahreiss Catalogue of nearby stars designates the binary system as GJ 195 The two components are then referred to individually as GJ 195 A and B 16 The two stars are reported to have a 3 5 visual magnitude difference 2 3 mag in the passband of the Gaia spacecraft although the difference is much smaller at infrared wavelengths This is unexpected and may indicate further unseen companions 12 The mass of the stars can in principle be determined from the orbital motion but uncertainties in the orbit have led to widely varying results In 1975 an eccentric 388 year orbit gave masses of 0 65 M and 0 13 M 75 A smaller near circular orbit published in 2015 had a 300 year orbit benefitting from mass constraints of 0 57 M and 0 53 M respectively for GJ 195 A and B based on their infrared magnitudes 12 Visual companions edit Six visual companions to Capella were discovered before Capella H and are generally known only as Capella B through G None are thought to be physically associated with Capella although all appear closer in the sky than the HL pair 69 Multiple double star designation WDS 05167 4600 27 Component Primary Rightascension a Equinox J2000 0 Declination d Equinox J2000 0 Epoch ofobservedseparation Angulardistancefromprimary Positionangle relativeto primary Apparent magnitude V Databasereference B A05h 16m 42 7s 46 00 55 1898 46 6 23 17 1 C A05h 16m 35 9s 46 01 12 1878 78 2 318 15 1 D A05h 16m 40 1s 45 58 07 1878 126 2 183 13 6 E A05h 16 5m 46 02 1908 154 1 319 12 1 F A05h 16m 48 748s 45 58 30 84 1999 112 0 137 10 21SIMBAD G A05h 16m 31 852s 46 08 27 42 2003 522 4 349 8 10SIMBAD Component F is also known as TYC 3358 3142 1 It is listed with a spectral type of K 76 although it is included in a catalogue of OB stars as a distant luminous star 77 Component G is BD 45 1076 with a spectral type of F0 76 at a distance of 401 light years 123 parsecs 78 It is identified as a variable member of the Guide Star Catalogue from Chandra observations although it is not known what type of variability 79 It is known to be an X ray source with an active corona 78 Several other stars have also been catalogued as companions to Capella 27 Components I Q and R are 13th magnitude stars at distances of 92 133 and 134 80 V538 Aurigae and its close companion HD 233153 are red dwarfs ten degrees away from Capella they have very similar space motions but the small difference makes it possible that this is just a coincidence 81 Two faint stars have been discovered by speckle imaging in the Capella HL field around 10 distant from that pair These have been catalogued as Capella O and P It is not known whether they are physically associated with the red dwarf binary 82 Etymology and culture editCapella traditionally marks the left shoulder of the constellation s eponymous charioteer or according to the 2nd century astronomer Ptolemy s Almagest the goat that the charioteer is carrying In Bayer s 1603 work Uranometria Capella marks the charioteer s back 83 The three Haedi had been identified as a separate constellation by Pliny the Elder and Manilius and were called Capra Caper or Hircus all of which relate to its status as the goat star 40 Ptolemy merged the Charioteer and the Goats in the 2nd century Almagest 84 In Greek mythology the star represented the goat Amalthea that suckled Zeus It was this goat whose horn after accidentally being broken off by Zeus was transformed into the Cornucopia or horn of plenty which would be filled with whatever its owner desired 37 Though most often associated with Amalthea Capella has sometimes been associated with Amalthea s owner a nymph The myth of the nymph says that the goat s hideous appearance resembling a Gorgon was partially responsible for the Titans defeat after Zeus skinned the goat and wore it as his aegis 85 In medieval accounts it bore the uncommon name Alhajoth also spelled Alhaior Althaiot Alhaiset Alhatod Alhojet Alanac Alanat Alioc which especially the last may be a corruption of its Arabic name العيوق al cayyuq 86 cAyyuq has no clear significance in Arabic 87 but may be an Arabized form of the Greek ai3 aiks goat cf the modern Greek Aiga Aiga the feminine of goat 86 To the Bedouin of the Negev and Sinai Capella al Ayyuq ath Thurayya Capella of the Pleiades from its role as pointing out the position of that asterism 88 Another name in Arabic was Al Rakib the driver a translation of the Greek 86 To the ancient Balts Capella was known as Perkuno Ozka Thunder s Goat or Tikutis 89 Conversely in Slavic Macedonian folklore Capella was Jastreb the hawk flying high above and ready to pounce on Mother Hen the Pleiades and the Rooster Nath 90 Astrologically Capella portends civic and military honors and wealth 39 In the Middle Ages it was considered a Behenian fixed star with the stone sapphire and the plants horehound mint mugwort and mandrake as attributes Cornelius Agrippa listed its kabbalistic sign nbsp with the name Hircus Latin for goat 91 92 In Hindu mythology Capella was seen as the heart of Brahma Brahma Hṛdaya 39 In traditional Chinese astronomy Capella was part of the asterism 五車 Wŭ che English Five Chariots which consisted of Capella together with Beta Aurigae Theta Aurigae and Iota Aurigae as well as Beta Tauri 93 94 Since it was the second star in this asterism it has the Chinese name 五車二 Wŭ che er English Second of the Five Chariots 95 In Quechua it was known as Colca 39 the Incas held the star in high regard 96 The Hawaiians saw Capella as part of an asterism Ke ka o Makali i The canoe bailer of Makali i that helped them navigate at sea Called Hoku lei star wreath it formed this asterism with Procyon Sirius Castor and Pollux 26 In Tahitian folklore Capella was Tahi ari i the wife of Fa a nui Auriga and mother of prince Ta urua Venus who sails his canoe across the sky 97 In Inuit astronomy Capella along with Menkalinan Beta Aurigae Pollux Beta Geminorum and Castor Alpha Geminorum formed a constellation Quturjuuk collar bones the two pairs of stars denoting a bone each Used for navigation and time keeping at night the constellation was recognised from Alaska to western Greenland 98 The Gwich in saw Capella and Menkalinan has forming shreets a įį vidzee the right ear of the large circumpolar constellation Yahdii which covered much of the night sky and whose orientation facilitated navigation and timekeeping 99 In Australian Aboriginal mythology for the Boorong people of Victoria Capella was Purra the kangaroo pursued and killed by the nearby Gemini twins Yurree Castor and Wanjel Pollux 100 The Wardaman people of northern Australia knew the star as Yagalal a ceremonial fish scale related to Guwamba the barramundi Aldebaran 101 Namesakes edit Capella a lunar crater to the north of the Mare Nectaris not named after the star USS Capella AK 13 and USNS Capella T AKR 293 both U S Navy ships Mazda Capella a model of automobile manufactured by MazdaSee also editCapella in fiction List of brightest stars List of nearest bright stars Historical brightest stars List of nearest giant starsNotes edit a b Pertains to the center of mass of the Capella Aa Ab binary system See Volume 1 The Hipparcos and Tycho Catalogues Archived 2018 09 01 at the Wayback Machine European Space Agency 1997 2 3 4 and the entry Archived 2016 03 03 at the Wayback Machine in the Hipparcos catalogue CDS ID I 239 Archived 2016 03 03 at the Wayback Machine the distance between the Earth and the Sun is one astronomical unit Polaris is only second magnitude The lithium abundance C12 C13 ratio and C N ratio have all declined in Capella Aa but not in Capella Ab References edit Capella Merriam Webster Retrieved 2022 05 09 a b c d e f van Leeuwen F November 2007 Validation of the new Hipparcos reduction Astronomy and Astrophysics 474 2 653 64 arXiv 0708 1752 Bibcode 2007A amp A 474 653V doi 10 1051 0004 6361 20078357 S2CID 18759600 a b c d e f g h Hoffleit Dorrit Jaschek Carlos 1991 The Bright star catalogue New Haven Conn Yale University Observatory 5th Rev ed Bibcode 1991bsc book H Petit M 1990 Catalogue of Variable or Suspected Stars Nearby the Sun Astronomy and Astrophysics Supplement 85 971 Bibcode 1990A amp AS 85 971P a b Roeser S Bastian U 1988 A new star catalogue of SAO type Astronomy and Astrophysics Supplement Series 74 449 Bibcode 1988A amp AS 74 449R ISSN 0365 0138 Eggen Olin J 1963 Three color photometry of the components in 228 wide double and multiple systems Astronomical Journal 68 483 Bibcode 1963AJ 68 483E doi 10 1086 109000 a b Cutri Roc M Skrutskie Michael F Van Dyk Schuyler D Beichman Charles A Carpenter John M Chester Thomas Cambresy Laurent Evans Tracey E Fowler John W Gizis John E Howard Elizabeth V Huchra John P Jarrett Thomas H Kopan Eugene L Kirkpatrick J Davy Light Robert M Marsh Kenneth A McCallon Howard L Schneider Stephen E Stiening Rae Sykes Matthew J Weinberg Martin D Wheaton William A Wheelock Sherry L Zacarias N 2003 VizieR Online Data Catalog 2MASS All Sky Catalog of Point Sources Cutri 2003 CDS ADC Collection of Electronic Catalogues 2246 II 246 Bibcode 2003yCat 2246 0C Agrawal P C Rao A R Sreekantan B V 1986 Study of quiescent state X ray emission from flare stars Monthly Notices of the Royal Astronomical Society 219 2 225 Bibcode 1986MNRAS 219 225A doi 10 1093 mnras 219 2 225 ISSN 0035 8711 a b Keenan Philip C McNeil Raymond C 1989 The Perkins Catalog of Revised MK Types for the Cooler Stars The Astrophysical Journal Supplement Series 71 245 Bibcode 1989ApJS 71 245K doi 10 1086 191373 a b Audard M 2002 Investigations of stellar coronae with XMM Newton 34th COSPAR Scientific Assembly Vol 34 Bibcode 2002cosp 34E1599A a b Samus N N Durlevich O V et al 2009 VizieR Online Data Catalog General Catalogue of Variable Stars Samus 2007 2013 VizieR On line Data Catalog B GCVS Originally Published in 2009yCat 102025S 1 B GCVS Bibcode 2009yCat 102025S a b c d e f g h i j k l m n o p q r s t u v w Torres Guillermo Claret Antonio Pavlovski Kresimir Dotter Aaron 2015 Capella a Aurigae Revisited New Binary Orbit Physical Properties and Evolutionary State The Astrophysical Journal 807 1 26 arXiv 1505 07461 Bibcode 2015ApJ 807 26T doi 10 1088 0004 637X 807 1 26 S2CID 55901109 a b c Strassmeier K G Fekel F C 1990 The spectral classification of chromospherically active binary stars with composite spectra Astronomy and Astrophysics 230 389 Bibcode 1990A amp A 230 389S a b c Stauffer J R Hartmann L W 1986 Chromospheric activity kinematics and metallicities of nearby M dwarfs The Astrophysical Journal Supplement Series 61 531 Bibcode 1986ApJS 61 531S doi 10 1086 191123 see Table 1 Joy Alfred H Abt Helmut A 1974 Spectral Types of M Dwarf Stars Astrophysical Journal Supplement 28 1 Bibcode 1974ApJS 28 1J doi 10 1086 190307 a b c d GJ 195 Archived 2017 11 07 at the Wayback Machine catalog entry Preliminary Version of the Third Catalogue of Nearby Stars Gliese Wilhelm Jahreiss H 1991 CDS ID V 70A Archived 2008 05 31 at the Wayback Machine Bidelman W P 1985 G P Kuiper s spectral classifications of proper motion stars Astrophysical Journal Supplement Series 59 197 Bibcode 1985ApJS 59 197B doi 10 1086 191069 ISSN 0067 0049 a b Brown A G A et al Gaia collaboration August 2018 Gaia Data Release 2 Summary of the contents and survey properties Astronomy amp Astrophysics 616 A1 arXiv 1804 09365 Bibcode 2018A amp A 616A 1G doi 10 1051 0004 6361 201833051 Gaia DR2 record for this source at VizieR Brown A G A et al Gaia collaboration 2021 Gaia Early Data Release 3 Summary of the contents and survey properties Astronomy amp Astrophysics 649 A1 arXiv 2012 01533 Bibcode 2021A amp A 649A 1G doi 10 1051 0004 6361 202039657 S2CID 227254300 Erratum doi 10 1051 0004 6361 202039657e Gaia EDR3 record for this source at VizieR a b c d e Leggett S K Allard F Berriman Graham 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Sources editAllen Richard Hinckley 2013 1899 Star Names Their Lore and Meaning Reprint ed Courier Corporation ISBN 978 0 486 13766 7 Burnham Robert Jr 1978 Burnham s Celestial Handbook An Observer s Guide to the Universe Beyond the Solar System Volume One Andromeda Cetus Revised amp Enlarged ed Dover Publications ISBN 978 0 486 23567 7 Ridpath Ian Tirion Wil 2001 Stars and Planets Guide Princeton University Press ISBN 978 0 691 08913 3 Brosch Noah 2008 Sirius Matters Springer Science amp Business Media ISBN 978 1 4020 8319 8 Schaaf Fred 2008 The Brightest Stars Discovering the Universe through the Sky s Most Brilliant Stars Wiley ISBN 978 0 470 24917 8 Winterburn Emily 2009 The Stargazer s Guide How to Read Our Night Sky Harper Perennial ISBN 978 0 06 178969 4 Portals nbsp Astronomy nbsp Stars nbsp Outer space Retrieved from https en wikipedia org w index php title Capella amp oldid 1213834304, wikipedia, wiki, book, books, library,

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