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Encyclopedia > Planetary system
An artist's concept of a planetary system
An artist's concept of a planetary system

A planetary system consists of the various non-stellar objects orbiting a star such as planets, moons, asteroids, meteoroids, comets, and cosmic dust.[1][2] The Sun together with its planetary system, which includes Earth, is known as the Solar System.[3][4] Look up stellar in Wiktionary, the free dictionary. ... Two bodies with a slight difference in mass orbiting around a common barycenter. ... This article is about the astronomical object. ... This article is about the astronomical term. ... A natural satellite is an object that orbits a planet or other body larger than itself and which is not man-made. ... For other uses, see Asteroid (disambiguation). ... “Meteor” redirects here. ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... “Space dust” redirects here. ... Sol redirects here. ... This article is about Earth as a planet. ... This article is about the Solar System. ...

Contents

Origin and Evolution

An artist's concept of a protoplanetary disk
An artist's concept of a protoplanetary disk

Planetary systems are generally believed to form as part of the same process which results in star formation. Some early theories involved another star passing extremely close to the Sun, drawing material out from it which then coalesced to form the planets. However, the probability of such a near collision is now known to be far too low to make this a viable model. Accepted theories today argue that a protoplanetary disk forms by gravitational collapse of a molecular cloud and then evolves into a planetary system by collisions and gravitational capture.[5] Image File history File links Artists concept of a protoplanetary disk. ... Image File history File links Artists concept of a protoplanetary disk. ... A protoplanetary disc (also protoplanetary disk, proplyd) is an accretion disc surrounding a T Tauri star. ... Star formation is the process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. ... A protoplanetary disc (also protoplanetary disk, proplyd) is an accretion disc surrounding a T Tauri star. ... A molecular cloud is a type of interstellar cloud whose density and size permits the formation of molecules, most commonly molecular hydrogen (H2). ...


Some planetary systems may form differently, however. Planets orbiting pulsarsstars which emit periodic bursts of electromagnetic radiation—have been discovered by the slight variations they cause in the timing of these bursts. Pulsars are formed in violent supernova explosions, and a normal planetary system could not possibly survive such a blast—planets would either evaporate, or the sudden loss of most of the mass of the central star would see them escape the gravitational hold of the star. One theory is that existing stellar companions were almost entirely evaporated by the supernova blast, leaving behind planet-sized bodies. Alternatively, planets may somehow form in the accretion disk surrounding pulsars.[6] It has been suggested that Radio pulsar be merged into this article or section. ... This article is about the astronomical object. ... This box:      Electromagnetic (EM) radiation is a self-propagating wave in space with electric and magnetic components. ... For other uses, see Supernova (disambiguation). ... An accretion disc (or accretion disk) is a structure formed by material falling into a gravitational source. ...


List of planetary systems

Artist's concept of a distant planetary system
Artist's concept of a distant planetary system
Our solar system compared with the planetary system of 55 Cancri
Our solar system compared with the planetary system of 55 Cancri

For a list of brown dwarfs, including those orbiting stars, see list of brown dwarfs. ... Image File history File links Extrasolar_planet_NASA2. ... Image File history File links Extrasolar_planet_NASA2. ... This article is about the Solar System. ... 55 Cancri (abbreviated 55 Cnc; Bayer designation ρ1 Cancri, Rho-1 Cancri) is a nearby 6th magnitude star in the constellation Cancer. ... This article is about the Solar System. ... Sol redirects here. ... PSR B1257+12 (sometimes abbreviated to PSR 1257+12) is a pulsar located 980 light years from Earth. ... It has been suggested that Radio pulsar be merged into this article or section. ... Pulsar planets are planets that are found orbiting pulsars. ... Upsilon Andromedae (υ And ) is a star, approximately 44 light-years from Earth, and approximately 3 billion years old, two thirds the age of our Sun. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ... PSR B1620-26 is also called PSR J1623-2631 (or or ) // System Configuration PSR B1620-26 is a pulsar in the globular cluster Messier 4 (or M4: see Messier object), about 5,600 light years from Earth in the constellation Scorpius. ... 55 Cancri (abbreviated 55 Cnc; Bayer designation ρ1 Cancri, Rho-1 Cancri) is a nearby 6th magnitude star in the constellation Cancer. ... is the 310th day of the year (311th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... Gliese 876 is a red dwarf star located approximately 15 light-years away in the constellation Aquarius. ... Red dwarfs constitute the majority of all stars According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type. ... In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other. ... HD 69830 is an orange dwarf star. ... 2M1207, 2M1207A or 2MASSW J1207334-393254 is a brown dwarf star located in the constellation Hydra; a companion object, 2M1207b, is believed to be one of the first extrasolar planets to be directly imaged, and is the first exoplanet to be discovered in orbit of a brown dwarf. ... This brown dwarf (smaller object) orbits the star Gliese 229, which is located in the constellation Lepus about 19 light years from Earth. ... Gliese 581 (IPA: ) is an M2. ... It has been suggested that Goldilocks phenomenon be merged into this article or section. ... Gliese 581 c (IPA: ) is a super-earth extrasolar planet orbiting the red dwarf star Gliese 581. ... Mu Arae (μ Ara / μ Arae) is a Sunlike yellow-orange star located around 50 light years away in the constellation Ara. ... HD 188753 is a triple star system approximately 149 light-years away in the constellation Cygnus. ... A triple star system consists of three gravitationally bound stars. ... HD 37124 is a yellow dwarf star (spectral type G4 IV-V) in the constellation of Taurus. ... HD 12661 is an orange star (spectral type K0) in the constellation of Aries. ... HD 73526 is a yellow dwarf star about 323 light-years away in the constellation Vela. ... 47 Ursae Majoris (abbreviated 47 UMa) is a 5th magnitude yellow dwarf star in the constellation of Ursa Major. ... Epsilon Eridani (ε Eri / ε Eridani) is a notable main-sequence K2 class star in the constellation of Eridanus. ... 14 Herculis is an orange dwarf star approximately 59 light-years away in the constellation Hercules. ...

See also

An extrasolar planet, or exoplanet, is a planet beyond the Solar System. ... For a list of brown dwarfs, including those orbiting stars, see list of brown dwarfs. ... A stellar nursery is a massive cosmic dust cloud in which microscopic particles may slowly aggregate due to gravitational attraction and eventually give rise to protostars and subsequently planetary systems, with one or more stars and planets. ... The planetary systems of stars other than the Sun and its Solar System are a staple element in much science fiction. ...

References

  1. ^ p. 394, The Universal Book of Astronomy, from the Andromeda Galaxy to the Zone of Avoidance, David J. Dsrling, Hoboken, New Jersey: Wiley, 2004. ISBN 0471265691.
  2. ^ p. 314, Collins Dictionary of Astronomy, Valerie Illingworth, London: Collins, 2000. ISBN 0-00-710297-6.
  3. ^ p. 382, Collins Dictionary of Astronomy.
  4. ^ p. 420, A Dictionary of Astronomy, Ian Ridpath, Oxford, New York: Oxford University Press, 2003. ISBN 0-19-860513-7.
  5. ^ planetary systems, formation of, David Darling, entry in The Internet Encyclopedia of Science, accessed on line September 23, 2007.
  6. ^ Planet formation scenarios, Philipp Podsiadlowski, pp. 149–165, in Planets around pulsars; Proceedings of the Conference, California Inst. of Technology, Pasadena, Apr. 30-May 1, 1992, edited by J. A. Phillips, J. E. Thorsest, and S. R. Kulkarni, ASP Conference Series, 36, 1993.
  7. ^ Wired News. "Found: Solar System Like Our Own", 2002-06-13. 
  8. ^ Whitney Clavin. "NASA's Spitzer Telescope Sees Signs of Alien Asteroid Belt", 2005-04-20. 
  9. ^ Christophe Lovis; Michel Mayor (2006-05-18). "Trio of Neptunes and their Belt".
  10. ^ Robert Roy Britt. "Likely First Photo of Planet Beyond the Solar System", 2004-09-10. 
  11. ^ "New planet found: It might hold life", San Francisco Chronicle, 2007-04-24. Retrieved on 2007-04-24. 
is the 266th day of the year (267th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... Also see: 2002 (number). ... is the 164th day of the year (165th in leap years) in the Gregorian calendar. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... is the 110th day of the year (111th in leap years) in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ... is the 138th day of the year (139th in leap years) in the Gregorian calendar. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... is the 253rd day of the year (254th in leap years) in the Gregorian calendar. ... Todays San Francisco Chronicle was founded in 1865 as The Daily Dramatic Chronicle by teenage brothers Charles de Young and Michael H. de Young. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 114th day of the year (115th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 114th day of the year (115th in leap years) in the Gregorian calendar. ...

 
 

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