Troy,
Long-period comets can last a very long time since they very infrequently
get close enough to the sun to lose much of their mass. Short-period
comets are former long-term comets whose orbits were drastically shortened
when they passed close to a planet, and so they also have existed for a
very long time.
Gordon Brown
Department of Mathematics
University of Colorado
Boulder, CO 80309-0395
This archive was generated by hypermail 2b29 : Wed Mar 20 2002 - 11:20:56 EST