C/2002
O7 (LINEAR) is a little-observed comet that will reach
perihelion on September 22nd 2003, at a heliocentric distance of
0.90AU, potentially close enough to the Sun to become a very interesting
object. Its poor positioning at perihelion, on the far side of the Sun and the
fact that it is an intrinsically small object mean that it will probably get no
brighter than magnitude 10. This is another of the cluster of moderately bright
comets at present with slightly hyperbolic orbits that mean that the comet has
come down from the Oort Cloud.
The
comet’s orbit is highly inclined (98º.7) and the comet will be in southern
polar skies when brightest, reaching a maximum southerly declination of –89º(!)
before moving back north as it fades.
C/2002
O7 (LINEAR) is evidently a first time object from the Oort Cloud. Although the
ephemeris offered by the Minor Planet Center based on an r4 law
suggests that it will get as bright as magnitude 7 just after perihelion, it is
more realistic to expect a much slower light curve evolution as is typical of
Oort Cloud objects unless they are particularly dusty.
As
the CCD light curve left shows, the comet is brightening at a good rate and
visual observers have been estimating close to magnitude 13 in April 2003, very
close to the MPC ephemeris prediction. However, this MPC ephemeris predicts
that the comet will brighten very quickly, reaching m1=10 by the end
of June 2003, something that seems fairly unlikely at present.
Seichii
Yoshida’s light curve is fitted by
m1 = 9.5 + 5 log Delta + 7.5 log r
and
predicts a maximum around magnitude 10 some time after perihelion. By this fit
the comet is a rather small and intrinsically faint object of which not too
much can be expected.
The
latest observations show an increasing dispersion in the data that may be due
to a faint extended coma.
The
images shown below reinforce this impression. Even at 2.4AU the comet shows
only a small coma and just a hint of a faint tail.
CCD observation in a 10
arcsecond aperture by:
Image: May 5th 2003
G.Degano, CAST (Talmassons,
Italy)
35-cm Newton + ST9-E CCD
Sum of 2x60s
A faint suggestion of a
tail can be appreciated to the east, but the comet remains faint and of low
activity.
Última actualización 12/06/2003
Por mrkidger