Comets are small, irregularly shaped objects composed of a mixture of rocks, dust, and what astronomers refer to as “ice” -- frozen water, methane, and ammonia. Most have highly elliptical orbits that bring them close to the Sun and then swing them deep into space, often beyond the orbit of Pluto.

When a comet is far from the Sun, it is frozen solid into a tiny nucleus.  But comets put on a spectacular show when they visit the inner solar system.  As a comet gets closer to the Sun, the surface of its nucleus warms.  Icy materials begin to sublime into gas.  As the gas boils off the comet, it can take small particles of dust with it.  The gas and dust forms a cloud of diffuse material, called a coma, that surrounds the nucleus.  The coma can swell to many times the size of the nucleus.  If the comet gets close enough to the Sun, the solar wind can blow gas and dust away from the comet, forming elongated and often multiple tails of gas and dust.  The tail always points away from the Sun -- not away from the comet’s direction of motion.

User Rating: / 10
PoorBest