What is a periodic comet?
Q: What is a periodic comet?
A: A periodic comet is a comet which orbits around the Sun. It can have either a short-period orbit, completing its orbit in less than 200 years, or a long-period orbit, taking more than 200 years to complete.
Q: Who are the Shoemaker-Levy comets named after?
A: The Shoemaker-Levy comets were named after Eugene Shoemaker, Carolyn Shoemaker and David Levy.
Q: How difficult is it to work out the orbit of a long-period comet?
A: It is very difficult to work out the orbit of a long-period comet because the orbit changes due to factors such as gravity from planets and gas or material released from the comet itself.
Q: How accurately can short-period comets be predicted?
A: Short-period comets can be predicted very accurately.
Q: What does Minor Planet Center do with regards to comets?
A: The Minor Planet Center, which is part of the International Astronomical Union, gives comets a different number prefix or uses their full title when naming them. For example 181P/Shoemaker-Levy and 192/Shoemaker-Levy would both be referred to as "Comet Shoemaker-Levy".
Q: Is there an informal numbering system for periodic comets?
A: Yes, there is an informal numbering system for periodic comets so that 181P would be Comet Shoemaker Levy 6 and 192P would be Comet Shoemaker Levy 1. This numbering system takes into account non periodical Shoemakers Levy's so there may appear gaps in numbers due to these being included in sequences.
Q: What does each letter before "/" signify when naming a comet?
A: When naming a comet, the letter before "/" signifies different things - "C" for non periodic; "P" for periodic; "D" for lost or disintegrated; "X" for no reliable orbit calculated (usually historical); and "A" if it was thought to be a comet but actually turns out to be minor planet.
