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.[7] 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.[7] The tail is created by millimeter-sized particles being pushed back by solar radiation pressure.[9][10]

354P/LINEAR

Main-belt object 354P/LINEAR (P/2010 A2) as seen in an 8 min photo with a 24" telescope
Discovery[1]
Discovered by	LINEAR (704)
Discovery date	2010-01-06
Designations
Minor planet category	Comet[2] Asteroid[3] Main-belt comet[4] Small Solar System body
Orbital characteristics[2]
Epoch 13 October 2010 (JD 2455482.5)
Aphelion	2.58 AU (Q)
Perihelion	2.01 AU (q)
Semi-major axis	2.29 AU (a)
Eccentricity	0.1246
Orbital period (sidereal)	3.47 yr
Mean anomaly	88.9° (M)
Inclination	5.25°
Longitude of ascending node	320°
Time of perihelion	2023-Oct-13[5]
Argument of perihelion	133°
Physical characteristics
Dimensions	220±40 m[6] ~140 m (460 ft)[7]
Albedo	unknown
Apparent magnitude	~18-20[1]
Absolute magnitude (H)	21.3±0.6[8]

Overview

P/2010 A2 was discovered on 6 January 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.[11][12] 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.[13] Beyond the frostline volatile ices are generally more common. Early observations did not detect water vapor or other gases.[7] 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.[6]

Observations with the Hubble Space Telescope[14] and the narrow angle camera on board the Rosetta spacecraft[15] 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.[16]

P/2010 A2 is likely about 150 meters (460 feet) in diameter.[7] Even when it was discovered it was suspected of being less than 500 meters in diameter.[17]

Another object, centaur 60558 Echeclus in 2006, was suspected of outgassing as a result of an undetermined splitting event.[18]

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.[7] The Flora family of asteroids may be the source of the Chicxulub (Cretaceous–Paleogene) impactor, the likely culprit in the extinction of the dinosaurs.[7]

Debris field? P/2010 A2 is likely the debris left over from a recent collision between two very small asteroids.

Comet nucleus Assumed comet nucleus seen to the lower left of debris field

See also

• 311P/PANSTARRS

Possible asteroid collision events

• 596 Scheila
• 493 Griseldis

References

External links

• Orbital simulation from JPL (Java) / Horizons Ephemeris
• Image of Comet P/2010 A2 (Muler 12" Meade LX200)
• Suspected Asteroid Collision Leaves Odd X-Pattern of Trailing Debris (Hubble Space Telescope WFC3 2010 January 29 image)
• Hubblesite Videos (January 29 through May 29)
• NOAO/WIYN: New Camera at WIYN images an Asteroid with a Long Tail (NOAO 13-07 : 3 June 2013)
• Jewitt, David; Ishiguro, Masateru; Agarwal, Jessica (2013). "Large Particles in Active Asteroid P/2010 A2". The Astrophysical Journal. 764 (1): L5. arXiv:1301.2566. Bibcode:2013ApJ...764L...5J. doi:10.1088/2041-8205/764/1/L5. S2CID 37325835.

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