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IAUC 8552: 2005cr; 165P

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                                                  Circular No. 8552
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 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  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)


SUPERNOVA 2005cr
     R. Quimby, P. Mondol, and F. Castro, University of Texas,
report the discovery of an apparent supernova in unfiltered CCD
images taken on June 24.17 (at mag about 16.5) and 26.17 UT (mag
about 15.9) using the 0.45-m ROTSE-IIIb telescope at the McDonald
Observatory.  The new object is located at R.A. = 12h22m17s.21,
Decl. = +12o23'49".3 (equinox 2000.0), which is 3" east and 1"
north the center of the apparent host galaxy.  ROTSE-IIIb images
taken June 8.17 show nothing at this location (limiting mag about
17.5).


COMETS 165P/2000 B4, 166P/2001 T4, AND 167P/2004 PY_42
     The recognition that the "centaur" 2004 PY_42 is a comet (cf.
IAUC 8545) brings up the inconsistency that the usual rules imply
that, as a comet, this object would not qualify for receiving a 'P/'
number until after it passes aphelion in the 2030s, whereas if it
had "remained" listed with only a minor-planet designation -- until
someone noticed its cometary activity next year, say -- it would
have qualified for numbering at the present opposition.  Indeed,
under that circumstance, 2004 PY_42 would presumably have received
"dual status", like the prototype centaur-class object (2060) =
95P/Chiron.  The purpose of comet numbering is to produce a
consistent set of generally predictable comets (except for the few
well-known cases of previously well-observed comets with 'D/'
prefixes that now no longer seem to exist), and that is best
accomplished by requiring observations at two (or more) perihelion
passages.  With their large perihelion distances (and evident large
sizes), "centaur comets" would seem less likely (over a rather
considerable timespan) than the more typical short-period comets
either physically to disappear or to experience significant
nongravitational effects in their motions.  It therefore seems
reasonable to use the same criteria for numbering both "cometary"
and "asteroidal" centaurs (and, for that matter, TNOs), namely, a
certain level of 'orbital quality' (cf. MPC 54279) plus
observations at four or more oppositions (at least one of which is
recent).  Accordingly (cf. MPC 54304), C/2004 PY_42 (CINEOS) is
being numbered (as 167P), as also are C/2000 B4 (165P/LINEAR) and
C/2001 T4 (166P/NEAT).  Of course, following cometary "tradition",
the names of these three centaurs are those of their discoverers
(or, rather, discovery programs), rather than the mythological
centaur names of the tradition for minor planets; there does not
seem to be an easy resolution to this particular dilemma, other
than to concentrate on referring to objects by their numbers and
provisional designations, rather than by their names.

                      (C) Copyright 2005 CBAT
2005 June 27                   (8552)            Daniel W. E. Green

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