Comet-like object P/2010 A2 was discovered
by the LINEAR survey on January 6, 2010. Service observations carried out using ACAM on the William Herschel Telescope on January
21, 2010, show an asteroidal nucleus detached from the dust tail (see
Figure 1). 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).
Figure 1. Image of the nucleus of P/2010 A2 (indicated with an arrow) and
the dust tail, detached from the asteroid. This image was obtained with
ACAM on the WHT on January 21, 2010. The x- and y-axes are labelled in
kilometers, and the direction of the Sun is to the right. This object is
the first Main-Belt Comet discovered at heliocentric distances as
small as 2 AU (figure extracted from F. Moreno et al., 2010, ApJ, 718, L132). [ JPEG | TIFF ].
Modelling of the dust feature indicates that the asteroid became active in late
March 2009, reached maximum activity in early June 2009 with
a dust loss mass rate of about 5 kg/s, and ceased activity in early
December 2009. The size of the particles ejected was between 0.001 and 1 cm, with speeds compatible with water-ice-drive
cometary activity at such heliocentric distances.
The diameter of the
asteroid is estimated at 220±40 m, and dust in the tail accounts for about 0.3% of the object mass.
While the event may have been triggered by a collision, this cannot be
confirmed with the available observations, but in any case the models
indicate that sustained activity over a period of some eight months
is required to explain the observations.
F. Moreno, J. Licandro, G.-P. Tozzi, J.L. Ortiz, A. Cabrera-Lavers, T. Augusteijn, T. Liimets, J.E. Lindberg, T. Pursimo, P. Rodríguez-Gil, O. Vaduvescu, 2009,
"Water-ice driven activity on Main-Belt Comet P/2010 A2 (LINEAR) ?", ApJ, 718, L132. Astro-ph | ApJ.