77P/Longmore

Comet 77P/Longmore was discovered by Andrew Longmore on a plate exposed with the 1.2-m UK Schmidt Telescope at Siding Spring Observatory (Australia) on June 10th 1975. The comet was magnitude 17 with a short tail. Although it was some time before a good orbit could be calculated it appeared to be of short period. The orbit was finally confirmed as being of 6.98 years period. 77P/Longmore has been seen at 5 apparitions (1974, 1981, 1988, 1995, & 2002). The orbital period reduced from 6.98 years to 6.83 years at its 2002 return corresponding to a decrease in the perihelion distance from the previous 2.40AU to 2.31AU. The comet brightens rapidly during its approach to perihelion, but its relatively large perihelion distance means that the comet never gets much brighter than magnitude 15.

The light curve

The light curve here is made up of CCD photometry in R with a 10" aperture taken by Ramón Naves & Montse Campàs (MPC 213) and by Rolando Ligustri & Paolo Beltrame (MPC 235).

The comet has been poorly observed, particularly at its 1995 return at which Seichii Yoshida suggests that the best fit to the data was given by m1 = 7.0 + 5 log Delta + 20 log r.  In 2002 he finds a similar, although rather brighter fit of m1 = 4.5 + 5 log Delta + 25 log r based on a much better coverage. The peak brightness was reached at opposition in April 2002, some 6 months before perihelion. Unfortunately, the circumstances of observation made the comet totally unobservable for some 14 months around perihelion and very few observations were made anywhere in the world post-perihelion. The coverage presented here ends 4 months pre-perihelion.

 The observations show only a slow increase in Afrho pre-perihelion, with the value rising from about 30-cm at T-206 days, to about 45-cm at T-127 days.

Despite the high power law fit to the light curve, this indicates that dust production increased only slowly, as r-2.7, with the comet’s approach to perihelion.

 

 

 

  

 

 

 

 

 

CCD observations in a 10 arcsecond aperture from:

CCD total magnitudes estimates in an aperture of 0'.2 by:

 

 


Última actualización 16/01/2003