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                                                  Circular No. 6076
Central Bureau for Astronomical Telegrams
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

1993 SC, 1993 RO
     These two transneptunian objects were recovered by M. Kidger
(on Aug. 15 and 16 with the 2.5-m Isaac Newton reflector) and by
D. Jewitt and J. Luu (on Sept. 5 and 7 with the 10-m Keck reflector and
University of Hawaii 2.2-m reflector), respectively.  General orbit
solutions indicate a = 41.4 AU, e = 0.27 and a = 40.5 AU, e = 0.25,
figures that tend to support the undersigned's hypothesis (IAUC
5983, 5985) that orbital stability is maintained by the 2:3 mean-motion
resonance with Neptune.  The new observations, together with orbital
elements that assume this hypothesis, are given on MPEC 1994-Q04 and
1994-R06.  It is important to note that the validity of the hypothesis
has not been proven, and further observations are required in order to
demonstrate whether the orbits are in fact stable.

     At a meeting on Aug. 24 the IAU General Assembly adopted a resolution
that will result in a change in the cometary designation system effective
1995 Jan. 1.  The present year/letter and year/Roman numeral systems
will be replaced by a single system resembling that for minor planets,
with objects recorded by the halfmonth.  Thus the third comet reported as
discovered during the second half of Feb. 1995 would be designated 1995 D3.
Much of the rationale for the change stems from the difficulty that is
sometimes apparent in deciding whether a particular object is in fact
a comet or a minor planet (e.g., 2060 Chiron, 1990 UL3 = 1990p = 1990 XVI
P/Shoemaker-Levy 2, 1977t = 1977 YA, etc.).  When appropriate, the nature
--or suggested nature--of an object can be indictated by preceding the
designation with A/ (for minor planet), C/ (for comet), P/ (as now, for
periodic comet), etc.  In a process analogous to the permanent numbering
of minor planets, sequential numbers will be defined for comets whose
periodicity has been well established, and in such cases these numbers
should immediately precede the P/ notation; "routine" recoveries of
these periodic comets will not in the future receive additional designations.
The system also allows the recognition of components of comets that have
split, of cometary images that have been noted on the Palomar Sky Survey
(for example), and the indication that some periodic comets have been lost
(or, in one recent famous case, destroyed).  The IAU resolution, which was
published in its entirety on MPC 23803-23804 on Aug. 28, also touched
briefly upon the matter of comet names.  It affirmed the intent "to retain
in general terms the tradition of naming comets for their discoverers"
while at the same time noting the need "to ensure fairness and simplicity".

1994 September 10              (6076)              Brian G. Marsden

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