Comets

Cosmic snowballs of frozen gases, rock, and dust that orbit the Sun. When close to the Sun, they heat up and release gases, forming a glowing head (coma) and spectacular tails that can stretch millions of kilometers.

• 01

  Comet tails always point away from the Sun

• 02

  Halley's Comet returns every 75-76 years

• 03

  The nucleus is typically 1-10 km across

• 04

  Comets may have brought water to early Earth

• 05

  There are over 3,700 known comets

• 06

  Some comets take millions of years to orbit the Sun

• 07

  Comet 67P was visited by the Rosetta spacecraft

• 08

  Comets have two tails: dust and ion