ESA Science & Technology - Anatomy of a comet - infographic

The main components of a comet – nucleus, coma, hydrogen envelope, dust and plasma tails – indicating their composition, relative sizes and location. Below, the two main reservoirs of comets in the Solar System are shown: the Kuiper Belt and the Oort Cloud. As an example, the orbits of three famous comets are also included: two short-period comets, 67P/Churyumov–Gerasimenko (the target of ESA's Rosetta mission) and 1P/Halley, and a long-period comet, Siding Spring, which will reach its closest approach to the Sun in late 2014.

The diagrams are representative and not to scale.