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IAUC 5869: 1993 SB AND 1993 SC

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                                                  Circular No. 5869
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)


1993 SB AND 1993 SC
     Iwan P. Williams, Queen Mary and Westfield College, London; and
Alan Fitzsimmons and Donal O'Ceallaigh, Queen's University, Belfast,
report their detection of two faint asteroidal objects during Sept. 16-21
very slowly retrograding some 1-2 deg west of the vernal equinox point.
The observations were made with the 2.5-m Isaac Newton telescope and
and prime-focus CCD camera at La Palma and are given on MPEC 1993-S09
and 1993-S10, from which the following orbital data are extracted:

     Direct circular orbital elements and ephemeris for 1993 SB:

 Epoch = 1993 Sept. 10.0 TT        Arg.Lat. =   2.95
                                      Node  = 355.36    2000.0
     a = 33.1491 AU                   Incl. =   2.28

1993 TT     R. A. (2000) Decl.     Delta      r    Elong. Phase      V
Sept.20    23 53.92    - 0 31.5   32.145   33.149  178.7    0.0     23.2
     30    23 53.00    - 0 37.3   32.159   33.149  171.2    0.3     23.2
Oct. 10    23 52.11    - 0 43.0   32.203   33.149  161.1    0.6     23.2

     Direct circular orbital elements and ephemeris for 1993 SC:

 Epoch = 1993 Sept. 10.0 TT        Arg.Lat. =   3.80
                                      Node  = 354.96    2000.0
     a = 34.4515 AU                   Incl. =   5.58

1993 TT     R. A. (2000) Decl.     Delta      r    Elong. Phase      V
Sept.20    23 55.11    - 0 06.6   33.448   34.451  178.3    0.1     22.3
     30    23 54.22    - 0 12.1   33.460   34.451  171.6    0.2     22.4
Oct. 10    23 53.35    - 0 17.5   33.503   34.451  161.6    0.5     22.4

     As for 1993 RO and RP, the observations can also be satisfied by
parabolic orbits.  With now six very faint objects detected at current
distances beyond Neptune, and with many more discoveries presumably
likely, there is rapidly developing a very severe problem of securing
adequate astrometric follow-up, which is absolutely essential for
any understanding of this exciting development in the outer solar system.
Because of the innate indeterminacy of the orbit solutions, the problem
is much more severe than that involving main-belt asteroids in the early
nineteenth century, and all efforts should be made to ensure coverage of
each new object on two nights each month well through evening quadrature.


1993 September 22              (5869)              Brian G. Marsden

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