Comets Photo Index
Comets are relatively small objects and are members of the Solar System. The nucleus of a comet is typically less that 10 km in diameter and is composed of water ice, frozen gasses and dust particles. Most comets orbit the Sun in highly elliptical orbits. As a comet approaches the Sun, solar radiation warms the surface layers of the comet's nucleus which sublimates to produce an enormous shell of dust called the coma.
If the comet and its coma are large enough, solar radiation pressure and the solar wind can create tail behind the comet.
New comets are discovered every year as they approach the Sun from the far reaches of the outer Solar System. Most are faint are are only visible with a telescope. On rare rare occasions, a comet may become bright enough to be seen by the naked eye. Such an object is often a spectacular sight.
