Electronic Telegram No. 401
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html


(42355) 2002 CR_46
     K. S. Noll, Space Telescope Science Institute; W. M. Grundy,
Lowell Observatory; D. C. Stephens, Johns Hopkins University; and
H. F. Levison, Southwest Research Institute, report the detection
of a binary companion to this centaur-type object (MPECs 2002-C84,
2002-H53; MPS 50182) when at 16.68 AU from the earth on Jan.
20.410-20.426 UT with the High Resolution Camera (+ clear filter)
of the Advanced Camera for Surveys on the Hubble Space Telescope
as part of an ongoing observing program.  The minor planet was
observed with one 300-sec exposure at each of four dithered
positions on the detector.  Two components are clearly resolved
in each image and in the co-added image.  The fainter component
is approximately 1.2 magnitudes fainter than the brighter of the
two.  The two components are separated in the images by an angular
distance of 0".11 +/- 0".01, with the fainter component at p.a.
226 degrees as measured from the primary.  The spacecraft tracked
the motion of (42355) as it moved at an average rate of 0".085/min;
the relative position of the two components remained the same
during the orbit.  The projected separation of the objects in the
plane of the sky is 1330 +/- 130 km.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2006 CBAT
2006 February 15                 (CBET 401)               Daniel W. E. Green