METEOR,
in astronomy, small solid body entering a planet’s
atmosphere from outer space and raised to incandescence by the friction
resulting from its rapid motion. Brilliant meteors, known as fireballs,
occur singly and generally consist of a luminous head, followed
by a cometlike train of light that may persist for several minutes;
some, called bolides, have been seen to explode with a sound like
thunder. Fainter meteors, called shooting or falling stars, usually
occur singly and sporadically. At intervals, however, hundreds of
such meteors occur simultaneously and appear to emanate from a fixed
point. These swarms are called meteoric showers and are named after
the constellation in which they seem to have their point of origin.
Some appear annually on the same days of each year and are called
periodic showers; others occur infrequently at varying intervals.
The periods of meteoric showers generally coincide with those of
certain comets. Most meteors are dissipated in flight and fall to
the earth as dust; a meteor that reaches the surface of the earth
or another planet is called a meteorite.