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IAUC 5611: 1992 QB1

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                                                  Circular No. 5611
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM     EASYLINK 62794505
MARSDEN@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)


1992 QB1
     D. Jewitt, University of Hawaii; and J. Luu, University of
California at Berkeley, report the discovery of a very faint object with
very slow (3"/hour) retrograde near-opposition motion, detected in CCD
images obtained with the University of Hawaii's 2.2-m telescope at Mauna
Kea.  The object appears stellar in 0".8 seeing, with an apparent Mould
magnitude R = 22.8 +/- 0.2 measured in a 1".5-radius aperture and a
broadband color index V-R = +0.7 +/- 0.2.

     1992 UT             R.A. (2000) Decl.
     Aug. 30.45568    0 01 12.79   + 0 08 50.7
          30.59817    0 01 12.19   + 0 08 46.9
          31.52047    0 01 08.37   + 0 08 22.7
          31.61982    0 01 07.95   + 0 08 19.9
     Sept. 1.35448    0 01 04.90   + 0 08 00.6
           1.62225    0 01 03.76   + 0 07 53.3

     Computations by the undersigned indicate that 1992 QB1 is currently
between 37 and 59 AU from the earth but that the orbit (except for the
nodal longitude) is completely indeterminate.  Some solutions are
compatible with membership in the supposed "Kuiper Belt", but the object
could also be a comet in a near-parabolic orbit.  The particular
solution below is the direct circle (but a retrograde circle some 15 AU
larger in radius also fits); Jewitt and Luu note that a cometlike albedo
of 4 percent then implies a diameter of 200 km and that the red color
suggests a surface composition rich in organics.  Further precise
astrometry during the late-September dark run should eliminate some
possibilities, but a satisfactory definition of the orbit will clearly
require follow-up through the end of the year.  The object's phase angle
reaches a minimum of less than 0.01 deg around Sept. 22.5 UT.

     Epoch = 1992 Aug. 26.0 TT     Arg.lat. =   0.335
                                      Node  = 359.440   2000.0
     a = 41.197 AU                    Incl. =   2.334

1992 TT     R. A. (2000) Decl.     Delta      r    Elong. Phase      V
Sept.15     0 00.09    + 0 01.7   40.200   41.197  172.5    0.2     23.4
     25    23 59.33    - 0 03.1   40.195   41.197  177.5    0.1     23.4
Oct.  5    23 58.58    - 0 07.9   40.220   41.197  167.5    0.3     23.5
     15    23 57.87    - 0 12.5   40.275   41.197  157.4    0.5     23.5


1992 September 14              (5611)              Brian G. Marsden

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