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IAUC 9137: P/2010 H2

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                                                  Circular No. 9137
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  D. W. E. Green, Room 209; Department of
 Earth and Planetary Sciences; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
CBAT@IAU.ORG; CBATIAU@EPS.HARVARD.EDU
URL http://www.cfa.harvard.edu/iau/cbat.html  ISSN 0081-0304


COMET P/2010 H2 (VALES)
     As first announced on CBETs 2249 and 2253, observations of an
unusually bright asteroidal object (discovery observation tabulated
below), only 15 degrees from opposition, were reported by Jan Vales,
observing with the 0.60-m f/3.3 Cichocki reflector at Crni Vrh,
Slovenia; H. Mikuz writes that, while the discovery images show a
distinct stellar profile, follow-up images with the same telescope
on Apr. 16.84 UT show that the object had become diffuse with a
flatter profile than those of nearby stars of similar brightness.
The numerous observations reported after posting on the Minor
Planet Center's 'NEOCP' webpage soon made it clear that the object
was some 2.0-2.5 AU from the earth and therefore of absolute
magnitude 8-9.  It was also soon clear that there were no recent
observations of the object in the MPC files, and R. A. Kowalski has
confirmed that it was not present (down to V magnitude 20) in
frames of the relevant region obtained by the Catalina Sky Survey
as recently as Apr. 15.4.  Several observers in the day after
discovery indicated that the new object appeared slightly but
consistently larger than nearby field stars of similar brightness
-- with a coma becoming noticeable and growing in size over the
next several days.  E. Guido and G. Sostero compared the appearance
to that of comet 17P/Holmes in the early phases of its Oct. 2007
outburst.  Visual total-magnitude and coma-diameter estimates:  Apr.
16.45, 13.3, - (A. Hale, Cloudcroft, NM, U.S.A., 41-cm reflector;
stellar appearance); 16.66, 12.9, - (K. Yoshimoto, Yamaguchi-ken,
Japan, 25-cm reflector; stellar appearance; communicated by S.
Nakano); 16.98, 12.7 (J. J. Gonzalez, Asturias, Spain, 0.20-m
reflector; stellar appearance); 18.15, 11.7, 0'.5 (M. Goiato,
Aracatuba, Brazil, 22-cm reflector); 19.08, 11.5, 0'.7 (Goiato);
20.83, 12.7, 0'.4 (W. Hasubick, Buchloe, Germany, 44-cm reflector);
22.02, 11.5, 1' (Goiato).

     2010 UT             R.A. (2000) Decl.       Mag.   Observer
     Apr. 16.00831   13 39 25.17   + 4 45 49.5   12.6   Vales

The initial astrometry appeared on MPEC 2010-H12.  The object
passed 1.0 AU from Jupiter in March 1976 (not May, as suggested on
CBET 2253).  Revised orbital elements by B. G. Marsden from 636
observations, Apr. 16-24 (from MPEC 2010-H57):

     T = 2010 Mar.  8.872 TT          Peri. = 130.080
     e = 0.19244                      Node  =  64.262   2000.0
     q = 3.10923 AU                   Incl. =  14.269
       a =  3.85017 AU     n = 0.130462     P =   7.55 years

                      (C) Copyright 2010 CBAT
2010 April 25                  (9137)            Daniel W. E. Green

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