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 comet 354P/LINEAR - (=P/2010 A2 (LINEAR) = P/2017 B5)

Discovery:

Comet-like object P/2010 A2 was discovered by the LINEAR survey on January 6, 2010 as an 20th magnitude asteroidal object. But was found to show a cometary appearance by other astrometrists, notably Peter Birtwhistle, but whilst it has a tail, there is no distinctive central condensation. Service observations carried out using ACAM on the William Herschel Telescope on January 21, 2010, show an asteroidal nucleus detached from the dust tail . Owing to its orbital parameters and its cometary appearance, the object is classified as a main-belt comet, in other words, an activated asteroid from the main asteroid belt. Comet P/2010 A2's orbit is the nearest to the Sun known so far, for this kind of object (semi-major axis of 2.29 AU). The comet has an exceedingly short period of 3.5 years and was at perihelion at 2.0 AU in 2009 December. The orbit is typical of a main belt asteroid and it may be a small (less than 500 metres) carbonaceous type object.

Javier Licandro, G. P. Tozzi, and Tiina Liimets note:

On January 14 we obtained images of this object using the Nordic Optical Telescope in La Palma, and on Jan 15 we made the following report to the CBAT:"J. Licandro (Instituto de Astrof�sica de Canarias, Spain), G. P. Tozzi (INAF, O. di Arcetri), and Tiina Liimets (Nordic Optical Telescope, NOT, Spain & Tartu Obs., Estonia) report the presence of an object, probably an asteroid, 2 arcsec to the East of P/2010 A2 (LINEAR). Six images of 5 minute exposure time each were obtained on Jan. 14 using ALFOSC (Andalucia Faint Object Spectrograph and Camera) on the 2.6m NOT telescope at the "Roque de los Muchachos" Observatory (La Palma, Canary Islands, Spain). Four images were obtained in the R band and two in the V band, starting 22:41 ending 23:39 UT, in non-photometric but very good seeing (0.6 arcsec) conditions. The asteroid moves in the same direction and at the same rate as the comet. In adition, the P/2010 A2 (LINEAR) image does not show any central condensation and looks like a "dust swarm". It is 4 arcmin long and only about 5 arcsec wide (177.000 and 3700 km respectively at the comet distance) with a PA=277 degrees. These observations suggest a connection between the asteroid and the dust swarm. A short lived event, such as a collision, may have produced the observed dust ejecta.". Next night, Jan. 16, the object was observed with the 10.4m GTC telescope and we made the following report "J. Licandro (Instituto de Astrof�sica de Canarias, IAC, Spain), A. Cabrera-Lavers and G. G�mez (IAC & GTC Project Office, Spain) confirms the detection of an object, probably an asteroid, abut 2 arcsec to the East of P/2010 A2 (LINEAR), reported on Jan. 15 by Licandro et al. , on a series of 30s images obtained with the OSIRIS instrument on the 10.4m Gran Telescopio Canarias (GTC) at the "Roque de los Muchachos" Observatory (La Palma, Canary Islands, Spain), on Jan 16, starting 1:41 and ending 3:11 UT. A total of 54 images 30s exp. time each were obtained, 24 with the r, 18 with the i and 12 with the g sloan filters respectively. The object is visible in all images."

Richard Miles report:

A few images were taken of P/2010 A2 by Darryl Sergison using the 2.0-m Faulkes Telescope North on January 15 and these showed no evidence of condensations within the elongated coma however the seeing was not particularly good at the time. Another attempt stacking a dozen or so images when subarcsecond seeing is present will be necessary.

The Hubble Space Telescope took a spectacular image of the object on January 29. Z. Sekanina, Jet Propulsion Laboratory, writes that the orientations of the tail of this comet reported from the observations made between January 7 and 16 (IAUC 9105, 9109; CBET 2134) suggest its formation between January and August 2009. Because of the edge-on projection (with the earth only 2 to 3 degrees below the comet's orbital plane) it is not possible to decide whether the tail is a product of one or more brief emission events or continuous activity over a period of time. From the tail's length, the maximum solar radiation pressure acceleration exerted on the dust is estimated at about 0.1 percent of the solar gravitational acceleration, which implies that the smallest dust particles in the tail are about 1 mm in diameter (at an assumed density of 1 g/cm^3).

From the width of the tail, a lower limit on the normal component of the particle velocity is about 0.1 m/s. An improved estimate can be determined from the tail width around the time of the earth's crossing the orbital plane on 2010 February 9. [IAUC 9110, 2010 January 25]

[Source:]