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Main-belt object 354P/LINEAR (P/2010 A2) as seen in an 8 min photo with a 24" telescope
Discovered byLINEAR (704)
Discovery date2010-01-06
Main-belt comet[4]
Small Solar System body
Orbital characteristics[2]
Epoch 2010-Oct-13
Aphelion2.58 AU (Q)
Perihelion2.01 AU (q)
2.29 AU (a)
3.47 yr
88.9° (M)
Physical characteristics
Dimensions220±40 m[5]
~140 m (460 ft)[6]

354P/LINEAR (formerly P/2010 A2 (LINEAR)) is a small Solar System body that displayed characteristics of both an asteroid and a comet, and thus, was initially given a cometary designation.[1] Because it has the orbit of a main-belt asteroid and showed the tail of a comet, it was listed as a main-belt comet.[2][4] But within a month of discovery, an analysis of images by the Hubble telescope suggested that its tail was generated by dust and gravel resulting from a recent head-on collision between asteroids rather than from sublimation of cometary ice.[6] This was the first time a small-body collision had been observed; since then, minor planet 596 Scheila has also been seen to undergo a collision, in late 2010. The position of the nucleus was remarkable for being offset from the axis of the tail and outside the dust halo, a situation never before seen in a comet.[6] The tail is created by millimeter-sized particles being pushed back by solar radiation pressure.[8][9]


Orbit of P/2010 A2 at the time of its discovery

P/2010 A2 was discovered on January 6, 2010 by Lincoln Near-Earth Asteroid Research (LINEAR) using a 1-meter (36") reflecting telescope with a CCD camera.[1] It was LINEAR's 193rd comet discovery.[10][11] It has been observed over a 112-day arc of the 3.5 year orbit.[2] It appears to have come to perihelion (closest approach to the Sun) around the start of December 2009,[2] about a month before it was discovered.

With an aphelion (furthest distance from the Sun) of only 2.6 AU,[2] P/2010 A2 spends all of its time inside of the frostline at 2.7 AU.[12] Beyond the frostline volatile ices are generally more common. Early observations did not detect water vapor or other gases.[6] Within less than a month of its discovery it was doubtful that the tail of P/2010 A2 was generated via active outgassing from sublimation of ices hidden beneath the crust.[4] Early modeling indicated that the asteroid became active in late March 2009, reached maximum activity in early June 2009, and eased activity in early December 2009.[5]

Observations with the Hubble Space Telescope[13] and the narrow angle camera on board the Rosetta spacecraft[14] indicate that the dust trail seen was probably created by the impact of a small meter size object on the larger asteroid in February or March 2009, although it cannot be ruled out that the asteroid's rotation increased from solar radiation resulting in a loss of mass that formed a comet-like tail.[15]

P/2010 A2 is likely about 150 meters (460 feet) in diameter.[6] Even when it was discovered it was suspected of being less than 500 meters in diameter.[16]

Another object, centaur 60558 Echeclus in 2006, was suspected of outgassing as a result of an undetermined splitting event.[17]

The orbit of P/2010 A2 is consistent with membership in the Flora asteroid family, produced by collisional shattering more than 100 million years ago.[6] The Flora family of asteroids may be the source of the Chicxulub (Cretaceous–Paleogene) impactor, the likely culprit in the extinction of the dinosaurs.[6]

Debris field?
P-2010 A2 Tail Implies Powerful Collision.jpg
P/2010 A2 is likely the debris left over from a recent collision between two very small asteroids.
Comet nucleus
Asteroid P-2010 A2.jpg
Assumed comet nucleus seen to the lower left of debris field

See also[edit]

Possible asteroid collision events


  1. ^ a b c d Marsden, Brian G. (2010-01-07). "MPEC 2010-A32 : COMET P/2010 A2 (LINEAR)". IAU Minor Planet Center. Harvard-Smithsonian Center for Astrophysics. Retrieved 2010-01-14.
  2. ^ a b c d e f "JPL Small-Body Database Browser: P/2010 A2 (LINEAR)" (last observation: 2012-10-14; arc: 2.83 years). Retrieved 2010-02-03.
  3. ^ "When is a comet not a comet? Rosetta finds out". ESA News. 13 October 2010. Retrieved 2010-10-15.
  4. ^ a b c Jewitt, David C. "P/2010 A2 (LINEAR): The 5th Main-Belt Comet". UCLA (Department of Earth and Space Sciences). Retrieved 2010-01-20.
  5. ^ a b Méndez, Javier (23 July 2010). "Comet P/2010 A2, an Activated Asteroid from the Main Asteroid Belt". Isaac Newton Group of Telescopes (ING). Retrieved 2010-07-27.
  6. ^ a b c d e f g Harrington, J. D.; Villard, Ray (2010-02-02). "Suspected Asteroid Collision Leaves Trailing Debris". NASA Release : 10-029. Retrieved 2010-02-03.
  7. ^ This absolute asteroidal V magnitude has been calculated using comet/asteroid magnitude analysis software "Comet for Windows" from value of R = 23.0 ± 0.5 taken from IAU Circular No. 9109. The mean V-R color index for asteroids is +0.4 ± 0.1.
  8. ^ HST Sees Evidence of Colliding Asteroids, Astronomy Today, Feb.2, 2010
  9. ^ Jewitt, David C. "P/2010 A2 (LINEAR): Possible Asteroid Smash". UCLA (Department of Earth and Space Sciences). Retrieved 2010-02-03.
  10. ^ Hergenrother, Carl W.; The Curious Case of Comet LINEAR, The Transient Sky, January 10, 2010 (1.8-m telescope on Kitt Peak)
  11. ^ Catalogue of Comet Discoveries, Comethunter.de
  12. ^ "Glossary of Astronomical Terms (Ice line)". Glossary of Astronomical Terms. Archived from the original on 2010-02-14. Retrieved 2010-01-20.
  13. ^ Jewitt, David C.; Weaver, Harold; Agarwal, Jessica; Mutchler, Max; et al. (2010). "A recent disruption of the main-belt asteroid P/2010?A2". Nature. 467 (7317): 817–9. Bibcode:2010Natur.467..817J. doi:10.1038/nature09456. PMID 20944743.
  14. ^ Snodgrass, Colin; Tubiana, Cecilia; Vincent, Jean-Baptiste; Sierks, Holger; Hviid, Stubbe; Moissl, Richard; Boehnhardt, Hermann; Barbieri, Cesare; et al. (2010). "A collision in 2009 as the origin of the debris trail of asteroid P/2010?A2". Nature. 467 (7317): 814–6. arXiv:1010.2883. Bibcode:2010Natur.467..814S. doi:10.1038/nature09453. PMID 20944742.
  15. ^ Harrington, J. D.; Weaver, Donna; Jewitt, David C. (October 13, 2010). "Hubble Finds that a Bizarre X-Shaped Intruder Is Linked to an Unseen Asteroid Collision". Hubblesite newscenter STScI-2010-34. Retrieved 2010-10-15.
  16. ^ Shanklin, Jonathan (2010-01-18). "BAA Comet Section : Comets discovered in 2010". Institute of Astronomy (British Astronomical Association). Retrieved 2010-01-21.
  17. ^ Hecht, Jeff (11 April 2006). "Hybrid comet-asteroid in mysterious break-up". NewScientist.com news service. Retrieved 2006-04-18.

External links[edit]