[IAUC] IAUC 9109: P/2010 A2 [25139-2010/01-R1]

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                                                  Circular No. 9109
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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COMET P/2010 A2 (LINEAR)
     Further to IAUC 9105, the following improved orbital elements
(from MPEC 2010-A78) for this comet are like those of a minor
planet in the inner part of the main belt:  T = 2009 Nov. 17.248 TT,
q = 1.97580 AU, e = 0.13178, Peri. = 125.600 deg, Node = 321.073
deg, i = 5.099 deg (equinox 2000.0), P = 3.43 years.
     J. V. Scotti, Lunar and Planetary Laboratory, reports that
there is no distinct nuclear condensation on CCD images of this
comet taken by R. S. McMillan with the Spacewatch 1.8-m f/2.7
reflector on Jan. 8.2 and 12.4 UT; on Jan. 8, the coma size was
about 8" x 11", with a sharper edge on the northern boundary, and a
long, narrow tail at least 4'.6 long in p.a. 279 deg; a faint spike
extended 0'.34 in p.a. 137 deg.
     D. Jewitt, University of California at Los Angeles; and J.
Annis and M. Soares-Santos, Fermilab, report observations of P/2010
A2 from Jan. 11 and 12 UT with the WYNN 3.5-m telescope on Kitt
Peak.  The object appears as a point-like body of red mag 23.0 +/-
0.5 located 2".5 +/- 0".5 east of the apex of a broad, low-surface-
brightness dust tail; the latter lacks strong condensation and is
more than 5' in length (see website URL
http://www2.ess.ucla.edu/~jewitt/MBC5.html).  The detected nucleus
is approximately 150-200 m in diameter (assuming albedo 0.1),
connected to the tail by an unresolved light bridge.  With
semimajor axis less than Jupiter's, and Tisserand parameter 3.6,
P/2010 A2 is the fifth recognized example of a main-belt comet (MBC),
differing from other MBCs in being an inner-belt object (orbit
consistent with membership in the Flora family).  The location of
the nucleus outside the tail suggests a recent impulsive origin for
P/2010 A2, perhaps from a recent collision between two previously
unseen minor planets, with radiation pressure driving the
separation between the nucleus and the tail.  In this scenario, the
bridge consists of large impact-produced particles slowly
separating from the nucleus under radiation pressure and Kepler
shear.  Future observations are encouraged to test this hypothesis.
     J. Licandro, Instituto de Astrofisica de Canarias; G. P. Tozzi,
Istituto Nazionale di Astrofisica, Arcetri; and T. Liimets, Nordic
Optical Telescope (NOT) and Tatru Observatory, report that 5-min R-
and V-band exposures obtained on Jan. 14.945-14.985 UT with the
2.5-m NOT (+ ALFOSC) shows the presence of an asteroidal object 2"
east of (and moving at the same rate as) the uncondensed "dust
swarm" of P/2010 A2, which itself is 4' long (177000 km at the
comet's distance) and about 5" wide in p.a. 277 deg.  Similar
reports of the comet's appearance have been received from other
observers, including R. Haver and L. Buzzi.

                      (C) Copyright 2010 CBAT
2010 January 19                (9109)            Daniel W. E. Green