The tail of a comet can be as long as 100 million miles. All comets have a center called a nucleus that meausures close to ten miles long. The hazy cloud surrounding the nucleus is known as the coma and can be as large as 1 million miles long. The coma along with the nucleus make up the comet's head.
Most comets travel around the sun in an oval shape path. The time it takes a comet to make a complete orbit is called its period. Some comets have very short periods of seven years, yet others have very long periods that they pass near the sun only once in thousands or even millions of years.
