This article is about naturally occurring objects. For astronomical objects of the Solar System, see List of Solar System objects. For artificial objects, see Satellite."Celestial object" and "Celestial body" redirect here. For the subtle body postulated in philosophy, see Body of light. For other uses, see Celestial.
An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists within the observable universe.[1] In astronomy, the terms object and body are often used interchangeably. However, an astronomical body or celestial body is a single, tightly bound, contiguous entity, while an astronomical or celestial object is a complex, less cohesively bound structure, which may consist of multiple bodies or even other objects with substructures.
Astronomical objects such as stars, planets, nebulae, asteroids and comets have been observed for thousands of years, although early cultures thought of these bodies as gods or deities. These early cultures found the movements of the bodies very important as they used these objects to help navigate over long distances, tell between the seasons, and to determine when to plant crops. During the Middle-Ages, cultures began to study the movements of these bodies more closely. Several astronomers of the Middle-East began to make detailed descriptions of stars and nebulae, and would make more accurate calendars based on the movements of these stars and planets. In Europe, astronomers focused more on devices to help study the celestial objects and creating textbooks, guides, and universities to teach people more about astronomy.
During the scientific revolution, in 1543, Nicolaus Copernicus'sheliocentric model was published. This model described the Earth, along with all of the other planets as being astronomical bodies which orbited around the Sun located in the center of the Solar System. Johannes Kepler discovered Kepler's laws of planetary motion, which are properties of the orbits which the astronomical bodies shared this was used to improve the heliocentric model. In 1584, Giordano Bruno proposed that all distant stars are their own suns, being the first in centuries to suggest this idea. Galileo Galilei was one of the first astronomers to use telescopes to observe the sky, in 1610 he observed four largest moons of Jupiter, now named the Galilean moons. Galileo also made observations of the phases of Venus, craters on the Moon, and sunspots on the Sun. Astronomer Edmond Halley was able to successfully predict the return of Halley's Comet, which now bears his name in 1758. In 1781, Sir William Herschel discovered the new planet Uranus, being the first discovered planet not visible by the naked eye.
In the 19th and 20th century, new technologies and scientific innovations allowed scientists to greatly expand their understanding of astronomy and astronomical objects. Larger telescopes and observatories began to be built and scientists began to print images of the Moon and other celestial bodies on photographic plates. New wavelengths of light unseen by the human eye were discovered, and new telescopes were made that made it possible to see astronomical objects in other wavelengths of light. Joseph von Fraunhofer and Angelo Secchi pioneered the field of spectroscopy, which allowed them to observe the composition of stars and nebulae, and many astronomers were able to determine the masses of binary stars based on their orbital elements. Computers began to be used to observe and study massive amounts of astronomical data on stars, and new technologies such as the photoelectricphotometer allowed astronomers to accurately measure the color and luminosity of stars, which allowed them to predict their temperature and mass. In 1913, the Hertzsprung-Russell diagram was developed by astronomers Ejnar Hertzsprung and Henry Norris Russell independently of each other, which plotted stars based on their luminosity and color and allowed astronomers to easily examine stars. It was found that stars commonly fell on a band of stars called the main-sequence stars on the diagram. A refined scheme for stellar classification was published in 1943 by William Wilson Morgan and Philip Childs Keenan based on the Hertzsprung-Russel Diagram. Astronomers also began debating whether other galaxies existed beyond the Milky Way, these debates ended when Edwin Hubble identified the Andromeda nebula as a different galaxy, along with many others far from the Milky Way.
Galaxy and largerEdit
The universe can be viewed as having a hierarchical structure.[2] At the largest scales, the fundamental component of assembly is the galaxy. Galaxies are organized into groups and clusters, often within larger superclusters, that are strung along great filaments between nearly empty voids, forming a web that spans the observable universe.[3]
The constituents of a galaxy are formed out of gaseous matter that assembles through gravitational self-attraction in a hierarchical manner. At this level, the resulting fundamental components are the stars, which are typically assembled in clusters from the various condensing nebulae.[6] The great variety of stellar forms are determined almost entirely by the mass, composition and evolutionary state of these stars. Stars may be found in multi-star systems that orbit about each other in a hierarchical organization. A planetary system and various minor objects such as asteroids, comets and debris, can form in a hierarchical process of accretion from the protoplanetary disks that surround newly formed stars.
The various distinctive types of stars are shown by the Hertzsprung–Russell diagram (H–R diagram)—a plot of absolute stellar luminosity versus surface temperature. Each star follows an evolutionary track across this diagram. If this track takes the star through a region containing an intrinsic variable type, then its physical properties can cause it to become a variable star. An example of this is the instability strip, a region of the H-R diagram that includes Delta Scuti, RR Lyrae and Cepheid variables.[7] The evolving star may eject some portion of its atmosphere to form a nebula, either steadily to form a planetary nebula or in a supernova explosion that leaves a remnant. Depending on the initial mass of the star and the presence or absence of a companion, a star may spend the last part of its life as a compact object; either a white dwarf, neutron star, or black hole.
Any natural Sun-orbiting body that has not reached hydrostatic equilibrium is classified by the IAU as a small Solar System body (SSSB). These come in many non-spherical shapes which are lumpy masses accreted haphazardly by in-falling dust and rock; not enough mass falls in to generate the heat needed to complete the rounding. Some SSSBs are just collections of relatively small rocks that are weakly held next to each other by gravity but are not actually fused into a single big bedrock. Some larger SSSBs are nearly round but have not reached hydrostatic equilibrium. The small Solar System body 4 Vesta is large enough to have undergone at least partial planetary differentiation.
Stars like the Sun are also spheroidal due to gravity's effects on their plasma, which is a free-flowing fluid. Ongoing stellar fusion is a much greater source of heat for stars compared to the initial heat released during formation.
Logarithmic representation of the observable universe with the notable astronomical objects known today. From down to up the celestial bodies are arranged according to their proximity to the Earth.
Infographic listing 210 notable astronomical objects marked on a central logarithmic map of the observable universe. A small view and some distinguishing features for each astronomical object are included.
^Task Group on Astronomical Designations from IAU Commission 5 (April 2008). "Naming Astronomical Objects". International Astronomical Union (IAU). from the original on 2 August 2010. Retrieved 4 July 2010.
^Narlikar, Jayant V. (1996). Elements of Cosmology. Universities Press. ISBN81-7371-043-0.
^Hartung, Ernst Johannes (1984-10-18). Astronomical Objects for Southern Telescopes. ISBN0521318874. Retrieved 13 February 2017.
^Elmegreen, Bruce G. (January 2010). "The nature and nurture of star clusters". Star clusters: basic galactic building blocks throughout time and space, Proceedings of the International Astronomical Union, IAU Symposium. Vol. 266. pp. 3–13. arXiv:0910.4638. Bibcode:2010IAUS..266....3E. doi:10.1017/S1743921309990809.
^Hansen, Carl J.; Kawaler, Steven D.; Trimble, Virginia (2004). Stellar interiors: physical principles, structure, and evolution. Astronomy and astrophysics library (2nd ed.). Springer. p. 86. ISBN0-387-20089-4.
External linksEdit
Wikimedia Commons has media related to Astronomical objects.
SkyChart, Sky & Telescope at the Library of Congress Web Archives (archived 2005-06-13)
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This article is about naturally occurring objects For astronomical objects of the Solar System see List of Solar System objects For artificial objects see Satellite Celestial object and Celestial body redirect here For the subtle body postulated in philosophy see Body of light For other uses see Celestial An astronomical object celestial object stellar object or heavenly body is a naturally occurring physical entity association or structure that exists within the observable universe 1 In astronomy the terms object and body are often used interchangeably However an astronomical body or celestial body is a single tightly bound contiguous entity while an astronomical or celestial object is a complex less cohesively bound structure which may consist of multiple bodies or even other objects with substructures Selection of astronomical bodies and objects Examples of astronomical objects include planetary systems star clusters nebulae and galaxies while asteroids moons planets and stars are astronomical bodies A comet may be identified as both body and object It is a body when referring to the frozen nucleus of ice and dust and an object when describing the entire comet with its diffuse coma and tail Contents 1 History 2 Galaxy and larger 3 Within a galaxy 4 Shape 5 Categories by location 6 See also 7 References 8 External linksHistory EditFurther information History of AstronomySee also Scientific Revolution and Copernican Revolution Astronomical objects such as stars planets nebulae asteroids and comets have been observed for thousands of years although early cultures thought of these bodies as gods or deities These early cultures found the movements of the bodies very important as they used these objects to help navigate over long distances tell between the seasons and to determine when to plant crops During the Middle Ages cultures began to study the movements of these bodies more closely Several astronomers of the Middle East began to make detailed descriptions of stars and nebulae and would make more accurate calendars based on the movements of these stars and planets In Europe astronomers focused more on devices to help study the celestial objects and creating textbooks guides and universities to teach people more about astronomy During the scientific revolution in 1543 Nicolaus Copernicus s heliocentric model was published This model described the Earth along with all of the other planets as being astronomical bodies which orbited around the Sun located in the center of the Solar System Johannes Kepler discovered Kepler s laws of planetary motion which are properties of the orbits which the astronomical bodies shared this was used to improve the heliocentric model In 1584 Giordano Bruno proposed that all distant stars are their own suns being the first in centuries to suggest this idea Galileo Galilei was one of the first astronomers to use telescopes to observe the sky in 1610 he observed four largest moons of Jupiter now named the Galilean moons Galileo also made observations of the phases of Venus craters on the Moon and sunspots on the Sun Astronomer Edmond Halley was able to successfully predict the return of Halley s Comet which now bears his name in 1758 In 1781 Sir William Herschel discovered the new planet Uranus being the first discovered planet not visible by the naked eye In the 19th and 20th century new technologies and scientific innovations allowed scientists to greatly expand their understanding of astronomy and astronomical objects Larger telescopes and observatories began to be built and scientists began to print images of the Moon and other celestial bodies on photographic plates New wavelengths of light unseen by the human eye were discovered and new telescopes were made that made it possible to see astronomical objects in other wavelengths of light Joseph von Fraunhofer and Angelo Secchi pioneered the field of spectroscopy which allowed them to observe the composition of stars and nebulae and many astronomers were able to determine the masses of binary stars based on their orbital elements Computers began to be used to observe and study massive amounts of astronomical data on stars and new technologies such as the photoelectric photometer allowed astronomers to accurately measure the color and luminosity of stars which allowed them to predict their temperature and mass In 1913 the Hertzsprung Russell diagram was developed by astronomers Ejnar Hertzsprung and Henry Norris Russell independently of each other which plotted stars based on their luminosity and color and allowed astronomers to easily examine stars It was found that stars commonly fell on a band of stars called the main sequence stars on the diagram A refined scheme for stellar classification was published in 1943 by William Wilson Morgan and Philip Childs Keenan based on the Hertzsprung Russel Diagram Astronomers also began debating whether other galaxies existed beyond the Milky Way these debates ended when Edwin Hubble identified the Andromeda nebula as a different galaxy along with many others far from the Milky Way Galaxy and larger EditThe universe can be viewed as having a hierarchical structure 2 At the largest scales the fundamental component of assembly is the galaxy Galaxies are organized into groups and clusters often within larger superclusters that are strung along great filaments between nearly empty voids forming a web that spans the observable universe 3 Galaxies have a variety of morphologies with irregular elliptical and disk like shapes depending on their formation and evolutionary histories including interaction with other galaxies which may lead to a merger 4 Disc galaxies encompass lenticular and spiral galaxies with features such as spiral arms and a distinct halo At the core most galaxies have a supermassive black hole which may result in an active galactic nucleus Galaxies can also have satellites in the form of dwarf galaxies and globular clusters 5 Within a galaxy EditThe constituents of a galaxy are formed out of gaseous matter that assembles through gravitational self attraction in a hierarchical manner At this level the resulting fundamental components are the stars which are typically assembled in clusters from the various condensing nebulae 6 The great variety of stellar forms are determined almost entirely by the mass composition and evolutionary state of these stars Stars may be found in multi star systems that orbit about each other in a hierarchical organization A planetary system and various minor objects such as asteroids comets and debris can form in a hierarchical process of accretion from the protoplanetary disks that surround newly formed stars The various distinctive types of stars are shown by the Hertzsprung Russell diagram H R diagram a plot of absolute stellar luminosity versus surface temperature Each star follows an evolutionary track across this diagram If this track takes the star through a region containing an intrinsic variable type then its physical properties can cause it to become a variable star An example of this is the instability strip a region of the H R diagram that includes Delta Scuti RR Lyrae and Cepheid variables 7 The evolving star may eject some portion of its atmosphere to form a nebula either steadily to form a planetary nebula or in a supernova explosion that leaves a remnant Depending on the initial mass of the star and the presence or absence of a companion a star may spend the last part of its life as a compact object either a white dwarf neutron star or black hole Shape EditFurther information Spherical Earth Cause See also Equatorial bulge and Hydrostatic equilibrium Planetary geology Composite image showing the round dwarf planet Ceres the slightly smaller mostly round Vesta and the much smaller much lumpier ErosThe IAU definitions of planet and dwarf planet require that a Sun orbiting astronomical body has undergone the rounding process to reach a roughly spherical shape an achievement known as hydrostatic equilibrium The same spheroidal shape can be seen from smaller rocky planets like Mars to gas giants like Jupiter Any natural Sun orbiting body that has not reached hydrostatic equilibrium is classified by the IAU as a small Solar System body SSSB These come in many non spherical shapes which are lumpy masses accreted haphazardly by in falling dust and rock not enough mass falls in to generate the heat needed to complete the rounding Some SSSBs are just collections of relatively small rocks that are weakly held next to each other by gravity but are not actually fused into a single big bedrock Some larger SSSBs are nearly round but have not reached hydrostatic equilibrium The small Solar System body 4 Vesta is large enough to have undergone at least partial planetary differentiation Stars like the Sun are also spheroidal due to gravity s effects on their plasma which is a free flowing fluid Ongoing stellar fusion is a much greater source of heat for stars compared to the initial heat released during formation Categories by location EditSee also Lists of astronomical objects See also List of Solar System objects by size The table below lists the general categories of bodies and objects by their location or structure Solar bodies Extrasolar Observable universeSimple bodies Compound objects Extended objectsSolar System Terrestrial planet Giant planet Gas giant Ice giant Heliosphere Oort cloud Hills Cloud Meteoroid Micrometeoroid Meteor Bolide Moons Moonlets Subsatellites hypothet Minor planets see below Asteroids Dwarf planets Moons Binaries Synestia hypothet Planets see below Ring system Trans Neptunian objects Small Solar System body Comets Planetesimal Contact binary SunPlanets Mercury Venus Earth Moon Mars moons Jupiter moons Saturn moons Uranus moons Neptune moonsDwarf planets Pluto moons Eris Dysnomia Ceres Makemake moon Haumea moons OthersMinor planets Vulcanoids hypothet ꞌAyloꞌchaxnims Atiras Near Earth objects PHO Arjunas Atens Apollos Amors Mars crossers Asteroid belt families Alindas Cybeles Eos Floras Hildas Hungarias Hygieas Koronis Marias Nysas Pallas Phocaeas Themis Vesta Trojans Earth Mars Jupiter Uranus Neptune Centaurs Damocloids Kuiper belt objects Classical KBOs Resonant TNOs Plutinos 2 3 Twotinos 1 2 Scattered disc objects Detached objects Sednoid Exoplanets Chthonian theoret Earth analog Eccentric Jupiter Exomoon Tidally detached exomoon Exocomet Hot Jupiter Hot Neptune Rogue planet Ocean theoret Pulsar planet Super Earth Tidally locked planet Eyeball planet theoret Toroidal planet theoret Trojan theoret USPBrown dwarfs Types M L T Y Sub brown dwarfsStars see sections below Stellar classification Stellar population III II I Peculiar star Stellar evolution Variable star Compact starBy luminosity evolution Protostar Young stellar object Pre main sequence Main sequence Subdwarfs Subgiants Giants Red Blue Bright giants Supergiants Red Blue Hypergiants Ultra cool dwarf Quasi star hypothet Compact stars see below Compact stars Black hole Stellar Intermediate mass Supermassive GRBs BBHs Exotic star hypothet Iron star hypothet Neutron star Blitzar hypothet Magnetar Pulsar Thorne Zytkow object hypothet Planck star hypothet Preon star hypothet Quark star hypothet Strange star hypothet White dwarf Black dwarf theoret By peculiar stars A type Peculiar Metallic Barium Blue straggler Carbon P Cygni S type Shell Wolf RayetVariables Extrinsic Rotating Alpha2 CVn Ellipsoidal Eclipsing binaries Algol Beta Lyrae W Ursae MajorisVariables Intrinsic Pulsating Cepheids W Virginis Delta Scuti RR Lyrae Mira Semiregular Irregular Beta Cephei Alpha Cygni RV Tauri Eruptive variables Flare stars T Tauri FU Orionis RCr Borealis Luminous blue Cataclysmic Symbiotics Micronova Dwarf nova Nova Supernova Type Ia Ib c II Hypernova GRBs Failed supernovaBy spectral types O blue B blue white A white F yellow white G yellow K orange M red Systems Planetary Star Stars in general Binary see below Triples Higher orderBinary stars By observation Optical Visual Astrometric Spectroscopic Eclipsing Close binaries Detached Semidetached Contact X ray BursterStellar groupings Star cluster Stellar association Open Globular Hypercompact Constellation AsterismGalaxies Galaxies in general Group and cluster Satellite galaxy Supercluster By component Bulge Spiral arm Thin disk Thick disk Halo Corona Tidal tail Stellar stream By morphology Spiral Barred spiral Lenticular Elliptical Ring Irregular By size Brightest cluster Giant elliptical Dwarf By type Protogalaxy Starburst Dark Active Radio Seyfert Quasar Microquasar Blazar OVV Red nugget Void galaxy Discs and media Interplanetary Dust cloud Medium Magnetic field Stellar disc Accretion Circumstellar Protoplanetary Debris Interstellar Cloud Medium ORCs Intergalactic Dust Medium ORCsNebulae Emission Planetary Supernova remnant Plerion H II region Reflection Dark nebulae Molecular cloud Bok globule Proplyd H I regionCosmic scale CMB Cosmic string hypothet Dark matter MACHO WIMP Domain wall hypothet Dust Filament LQG Void Supervoid Logarithmic representation of the observableuniverse with the notable astronomical objectsknown today From down to up the celestialbodies are arranged according to their proximityto the Earth Infographic listing 210 notable astronomicalobjects marked on a central logarithmic map ofthe observable universe A small view and somedistinguishing features for each astronomicalobject are included See also EditList of light sources List of Solar System objects List of Solar System objects by size Lists of astronomical objects Outer spaceReferences Edit Task Group on Astronomical Designations from IAU Commission 5 April 2008 Naming Astronomical Objects International Astronomical Union IAU Archived from the original on 2 August 2010 Retrieved 4 July 2010 Narlikar Jayant V 1996 Elements of Cosmology Universities Press ISBN 81 7371 043 0 Smolin Lee 1998 The life of the cosmos Oxford University Press US p 35 ISBN 0 19 512664 5 Buta Ronald James Corwin Harold G Odewahn Stephen C 2007 The de Vaucouleurs atlas of galaxies Cambridge University Press p 301 ISBN 978 0 521 82048 6 Hartung Ernst Johannes 1984 10 18 Astronomical Objects for Southern Telescopes ISBN 0521318874 Retrieved 13 February 2017 Elmegreen Bruce G January 2010 The nature and nurture of star clusters Star clusters basic galactic building blocks throughout time and space Proceedings of the International Astronomical Union IAU Symposium Vol 266 pp 3 13 arXiv 0910 4638 Bibcode 2010IAUS 266 3E doi 10 1017 S1743921309990809 Hansen Carl J Kawaler Steven D Trimble Virginia 2004 Stellar interiors physical principles structure and evolution Astronomy and astrophysics library 2nd ed Springer p 86 ISBN 0 387 20089 4 External links Edit Wikimedia Commons has media related to Astronomical objects SkyChart Sky amp Telescope at the Library of Congress Web Archives archived 2005 06 13 Monthly skymaps for every location on EarthPortals Astronomy Stars Spaceflight Outer space Solar System Retrieved from https en wikipedia org w index php title Astronomical object amp oldid 1171641048, wikipedia, wiki, book, books, library,
