Main-belt comet P/2010 A2 as seen in a 8 min photo with a 24" telescope
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Discovery[1]
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Discovered by | LINEAR (704) |
Discovery date | 2010-01-06 |
Designations
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Minor planet category |
Comet[2] Asteroid[3] Main-belt comet[4] Small Solar System body |
Epoch January 14, 2010 | |
Aphelion | 2.57 AU (Q) |
Perihelion | 2.00 AU (q) |
Semi-major axis | 2.29 AU (a) |
Eccentricity | 0.12 |
Orbital period | 3.47 yr |
Mean anomaly | 11.4° (M) |
Inclination | 5.26° |
Longitude of ascending node | 320° |
Argument of perihelion | 133° |
Physical characteristics
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Dimensions | 220±40 m[5] ~140 m (460 ft)[6] |
Albedo | unknown |
Apparent magnitude | ~18-20[1] |
Absolute magnitude (H) | 21.3±0.6[7] |
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] Since 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, 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 of 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]
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 can not 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 K/T impactor, the likely culprit in the extinction of the dinosaurs.[6]
P/2010 A2 is likely the debris left over from a recent collision between two very small asteroids. |
Assumed comet nucleus seen to the lower left of debris field |
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