Starguide - A Practical Guide to Astro-Photography

A comet is a small, icy, and dusty object orbiting the Sun. 

Comets formed in the outer Solar System, far away from the Sun where ice is stable. Most of them spend most of their time far beyond the orbit of Neptune, and all spend most of their time beyond Jupiter. Some have orbits that bring them occasionally through the inner Solar System including sometimes past Earth’s orbit. When they are in the inner Solar System and closer to the Sun’s influence, their ice sublimates — that is, it goes from ice directly to gas — kicking off dust and forming the coma and tails they are famous for.

Other free floating objects in our Solar system:

• Asteroid Definition
• Comet Definition
• Meteorite Definition
• Meteor Definition

Reference: Asteroids vs comets vs… | The Planetary Society

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