Tyche (hypothetical planet)

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Template:Distinguish2

For the asteroid, see 258 Tyche.
An artist's rendering of the Oort cloud and the Kuiper belt (inset)

Tyche (/ˈtaɪki/) is the nickname given to a hypothetical gas giant planet located in the Solar System's Oort cloud, first proposed in 1999 by astronomer John Matese of the University of Louisiana at Lafayette.[1][2] Matese and his colleague Daniel Whitmire argue that evidence of Tyche's existence can be seen in a supposed bias in the points of origin for long-period comets. They noted that Tyche, if it exists, should be detectable in the archive of data that was collected by NASA's Wide-field Infrared Survey Explorer (WISE) telescope.[3][4] However, several astronomers have voiced skepticism of this object's existence.[2][5] Analysis over the next couple of years will be needed to determine if WISE has actually detected such a world or not.[6]

History

Matese first proposed the existence of this planet in 1999,[7] based on his observations of the orbits of long-period comets. Most astronomers agree that long-period comets (those with orbits of thousands of years) have an isotropic distribution; that is, they arrive at random from every point in the sky.[8] Because comets are volatile and dissipate over time, astronomers suspect that they must be held in a spherical cloud tens of thousands of AU distant (known as the Oort cloud) for most of their existence.[8] However, Matese claimed that rather than arriving from random points across the sky as is commonly thought, comet orbits were in fact clustered in a band inclined to the orbital plane of the planets. Such clustering could be explained if they were disturbed by an unseen object at least as large as Jupiter, possibly a brown dwarf, located in the outer part of the Oort cloud.[9][10] He also suggested that such an object might also explain the trans-Neptunian object Sedna's peculiar orbit.[11] However, his sample size was small and the results were inconclusive.[5]

Orbit

Whitmire and Matese speculate that Tyche's orbit would lie at approximately 500 times Neptune's distance; equivalent to 15,000 AU (2.2×1012 km) from the Sun, a little less than one quarter of a light year. This is still well within the Oort cloud, whose boundary is estimated to be beyond 50,000 AU. It would have an orbital period of roughly 1.8 million years.[12] A failed search of older IRAS data suggests that an object of 5 MJ would need to have a distance greater than 10,000 AU.[3] Such a planet would orbit in a different plane in orientation to our current planet orbits,[13] and probably formed in a wide-binary orbit.[3] Wide binaries may form through capture during the dissolution of a star's birth cluster.[3]

Mass

General size comparison between a low-mass star, a brown dwarf, and the planets Jupiter and Earth.

Whitmire and Matese speculate that the hypothesized planet could be up to four times the mass of Jupiter and have a relatively high temperature of approximately 200 K[3] (−73°C), due to residual heat from its formation and Kelvin–Helmholtz heating.[14] It would be insufficiently massive to undergo nuclear fusion reactions in its interior, a process which occurs in objects above roughly 13 Jupiter masses. Although more massive than Jupiter, Tyche would be about Jupiter's size since degenerate pressure causes massive gas giants to increase only in density, not in size, relative to their mass.[a]

Origin of name

Tyche (Τύχη, meaning "fortune" or "luck" in Greek) was the Greek goddess of fortune and prosperity. The name was chosen to avoid confusion with an earlier similar hypothesis that the Sun has a dim companion named Nemesis, whose gravity triggers influxes of comets into the inner Solar System, leading to mass-extinctions on Earth. Tyche was the name of the "good sister" of Nemesis.[3] This name was first used for an outer Oort cloud object by Davy Kirpatrick at the Infrared Processing and Analysis Center of the California Institute of Technology.[15]

Ongoing research

The Wide-field Infrared Survey Explorer (WISE) space telescope has completed an all-sky infrared survey that includes areas where Whitmire and Matese anticipate that Tyche may be found.[3] On March 14, 2012, the entire catalog of the WISE mission was released.[16]

See also

Notes

  1. ^ A cold hydrogen-rich gas giant slightly more massive than Jupiter (below about 1.6 MJ) would be larger in volume than Jupiter,[17] but for higher masses, degenerate pressure will cause the planet to shrink,[17] and added mass is compensated for by increasing degeneracy pressure in the planetary core. For example, HD 17156 b is 3 MJ with a radius of 96% of Jupiter and HD 80606 b is 4 MJ with a radius of 92% of Jupiter. Even the brown dwarf COROT-3b (22 MJ) is estimated to be about the volume of Jupiter. After 10 billion years of cooling, large gas giants are all very nearly Jupiter's radius, but more massive objects are slightly smaller.[18]

References

  1. ^ Rodgers, Paul (February 13, 2011). "Up telescope! Search begins for giant new planet". The Independent. Retrieved February 14, 2011.
  2. ^ a b Wolchover, Natalie (February 15, 2011). "Article: Astronomers Doubt Giant Planet 'Tyche' Exists in Our Solar System". Space.com. Retrieved February 15, 2011.
  3. ^ a b c d e f g Matese, John J.; Whitmire, Daniel P. (2011). "Persistent evidence of a jovian mass solar companion in the Oort cloud" (PDF). Icarus. 211 (2): 926–938. arXiv:1004.4584. Bibcode:2011Icar..211..926M. doi:10.1016/j.icarus.2010.11.009.
  4. ^ Helhoski, Anna. "News 02/16/11 Does the Solar System Have Giant New Planet?". The Norwalk Daily Voice. Retrieved 10 July 2012.
  5. ^ a b Plait, Phil (February 14, 2011). "No, there's no proof of a giant planet in the outer Solar System". Discovery Magazine. Retrieved February 15, 2011.
  6. ^ Whitney Clavin (2011-02-18). "Can WISE Find the Hypothetical 'Tyche'?". NASA/JPL. Retrieved 2011-02-19.
  7. ^ Matese, John J.; Lissauer, Jack J. (May 6, 2002). "Continuing Evidence of an Impulsive Component of Oort Cloud Cometary Flux" (PDF). University of Louisiana at Lafayette, and NASA Ames Research Center. Retrieved March 21, 2008.
  8. ^ a b Harold F. Levison, Luke Donnes (2007). "Comet Populations and Cometary Dynamics". In Lucy Ann Adams McFadden, Lucy-Ann Adams, Paul Robert Weissman, Torrence V. Johnson (ed.). Encyclopedia of the Solar System (2nd ed.). Amsterdam; Boston: Academic Press. pp. 575–588. ISBN 0-12-088589-1.{{cite book}}: CS1 maint: multiple names: editors list (link)
  9. ^ Murray, John B. (1999). "Arguments for the Presence of a Distant Large Undiscovered Solar System Planet". Monthly Notices of the Royal Astronomical Society. 309 (1): 31–34. Bibcode:1999MNRAS.309...31M. doi:10.1046/j.1365-8711.1999.02806.x. {{cite journal}}: Unknown parameter |laydate= ignored (help); Unknown parameter |laysource= ignored (help); Unknown parameter |laysummary= ignored (help)
  10. ^ Matese, John J.; Whitman, Patrick G.; Whitmire, Daniel P . (1999). "Cometary Evidence of a Massive Body in the Outer Oort Clouds". Icarus. 141 (2): 354. Bibcode:1999Icar..141..354M. doi:10.1006/icar.1999.6177.
  11. ^ Matese, John J.; Whitmire, Daniel P.; Lissauer, Jack J. (2006). "A Widebinary Solar Companion as a Possible Origin of Sedna-like Objects". Earth, Moon, and Planets. 97 (3–4): 459–470. Bibcode:2005EM&P...97..459M. doi:10.1007/s11038-006-9078-6. Retrieved August 17, 2010.
  12. ^ "Orbital period of a planet at a distance of 15000 AU with a circular orbit". Retrieved February 15, 2011.
  13. ^ "Have UL Physicists Identified a New Planet?". University of Louisiana. 2011-02-14. Retrieved 2011-02-16.
  14. ^ "Search on for Tyche, believed to be largest planet in the Solar System". Daily Mail. Daily Mail. February 14, 2011. Retrieved February 14, 2011.
  15. ^ Sayanagi, Kunio M. (March 2, 2011). "Where is Tyche, the 10th 9th planet? Getting the full story". ArsTechnica. Retrieved March 21, 2011.
  16. ^ "NASA Releases New WISE Mission Catalog of Entire Infrared Sky". Nasa JPL. 2012-03-14. Retrieved 2012-03-15.
  17. ^ a b Seager, S. (2007). "Mass-Radius Relationships for Solid Exoplanets". The Astrophysical Journal. 669 (2): 1279–1297. arXiv:0707.2895. Bibcode:2007ApJ...669.1279S. doi:10.1086/521346. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help) The reference states 500 ME (1.6 MJ). Jupiter is 318 times more massive than the Earth.
  18. ^ Spiegel, David S. (2011). "The Deuterium-Burning Mass Limit for Brown Dwarfs and Giant Planets". The Astrophysical Journal. 727 (1): 57. arXiv:1008.5150. Bibcode:2011ApJ...727...57S. doi:10.1088/0004-637X/727/1/57. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
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