Comets#
Comets are remnant planetesimals from planet formation in the early Solar System and are considered some of the most pristine icy bodies in the Solar System
Composition#
Comets are composed of a nucleus made up from rock, dust and ice. Volatile molecules within the ice sublimate as a comet gets closer to the Sun creating a coma which is also composed of dust. The dust tail is mainly composed of silicates and a plasma tail forms from ionisation of the gas in the coma due to solar radiation.
Coma#
Classification#
Periodic comets, those which orbit the Sun, are broadly classified into two categories:
Short period comets#
- orbital period < 200 years
Thought to originate from the Kuiper belt. Their short period orbit brings them close to the Sun where the ice is processed.
Long period comets#
- orbital period > 200 years
(orbital period > 200 years) are thought to originate from the Oort Cloud. They have passed closer to the Sun less times than short period comets and are therefore less processed.