Asteroids are composed of a mixture of rock and metal which orbit the Sun. Because they are too small to be classified as planets, they are called minor planets. |
Comets are primarily composed of ice and dust, thus called "dirty snowballs"
by many involved with astronomy. They typically have orbits that range from a
few years to several hundred thousand years. Comets are not on fire. As
they approach the sun, the solar radiation melts the comet's ices and they
start to release dust particles which we see as the comet's tail. Comets rarely
come close to the Earth and therefore seem to be moving quite slowly. They are
usually visible for a period of several weeks to several months. |