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IAUC 8977: C/2008 S1; S/2008 (35107) 1

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                                                  Circular No. 8977
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://www.cfa.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)


COMET C/2008 S1 (McNAUGHT)
     R. H. McNaught reports his discovery of a comet (discovery
position tabulated below) with a 15" circular coma and possible
extension in p.a. about 30 deg on CCD images obtained with the 0.5-
m Uppsala Schmidt telescope; additional stacked images from Sept.
18.38 UT show a 30" coma extended to the north and a condensation
with FHWM = 5".  Following posting on the 'NEOCP' webpage, other
CCD observers have also reported cometary appearance.  D. Mayes and
J. Young (Table Mountain 0.6-m reflector, Sept. 18.1; low altitude)
report a round coma with an 8"-diameter central condensation and a
possible thin tail approximately 20" long in p.a. 55-60 deg.  E.
Guido, G. Sostero, and P. Camilleri (0.25-m reflector at Moorook,
Australia, remotely, Sept. 18.5; 31 co-added exposures) find a coma
diameter of about 12".  A. Herring measures a 9".9 tail in p.a.
59.4 deg on exposures taken by R. Holmes (Charleston, IL, U.S.A.,
0.61-m astrograph, Sept. 18.05-18.06).

     2008 UT             R.A. (2000) Decl.       Mag.
     Sept.17.40807   16 21 33.37   -24 29 41.3   16.6

The available astrometry, preliminary parabolic orbital elements (T
= 2008 Sept. 21.089 TT, q = 1.35320 AU, Peri. = 192.082 deg, Node =
104.558 deg, i = 17.974 deg, equinox 2000.0), and an ephemeris
appear on MPEC 2008-S10.


S/2008 (35107) 1
     W. J. Merline, Southwest Research Institute (SwRI); A. R.
Conrad, W. M. Keck Observatory (WMKO); J. D. Drummond, Starfire
Optical Range, AFRL; P. M. Tamblyn, Binary Astronomy, Dillon, CO,
and SwRI; C. Dumas and B. Carry, European Southern Observatory; R.
D. Campbell and R. W. Goodrich, WMKO; C. R. Chapman, SwRI; and W.
M. Owen, Jet Propulsion Laboratory, report the first-ever near-
infrared imaging of a close-approaching binary minor planet:  on
Aug. 9 UT, over a span of about 1 hr, they obtained J-, H-, and
K_p-band images -- using the 10-m Keck II Telescope (+ NIRC2/AO
adaptive-optics system) on Mauna Kea -- of clearly-separated
components of (35107) 1991 VH, which was first suspected as a
binary by Pravec et al. (IAUC 6607).  On Aug. 9.236 the satellite,
designated S/2008 (35107) 1, was 0".08 (projected separation 3.1
km) in p.a. 105 deg from the primary (the smallest angular and
physical separations yet for a binary minor planet using adaptive
optics).  The brightness difference was Delta(K_p) approximately
2.0 mag.  The observed separation and size ratio are consistent
with the parameters derived by Pravec et al. (2006, Icarus 181, 63).

                      (C) Copyright 2008 CBAT
2008 September 19              (8977)            Daniel W. E. Green

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