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