Comets can be a spectacular sight. A mixture of rock and dust bound together with ice and frozen gases, comets usually stay in the deep freeze of space, orbiting the Sun in the Kuiper Belt beyond Neptune or at the edge of the Solar System in the Oort Cloud.
Astronomers believe that comets are leftover debris from the collection of gas, ice, rocks, and dust that formed the Solar System about 4.6 billion years ago.
Short-period comets (orbits under 200 years) are probably nudged out of the Kuiper belt by the gravitational pull of the outer planets.
Long-period comets (orbits over 200 years) come from the Oort cloud, where gravitational interactions with passing stars can cause icy bodies to enter the inner Solar System and become active comets. (Image Right: Comet, Courtesy of NASA)
