<P> A comet tail -- and coma -- are features visible in comets when they are illuminated by the Sun and may become visible from Earth when a comet passes through the inner Solar System . As a comet approaches the inner Solar System , solar radiation causes the volatile materials within the comet to vaporize and stream out of the nucleus , carrying dust away with them . Separate tails are formed of dust and gases , becoming visible through different phenomena ; the dust reflects sunlight directly and the gases glow from ionisation . Most comets are too faint to be visible without the aid of a telescope , but a few each decade become bright enough to be visible to the naked eye . </P>
<P> A comet tail -- and coma -- are features visible in comets when they are illuminated by the Sun and may become visible from Earth when a comet passes through the inner Solar System . As a comet approaches the inner Solar System , solar radiation causes the volatile materials within the comet to vaporize and stream out of the nucleus , carrying dust away with them . Separate tails are formed of dust and gases , becoming visible through different phenomena ; the dust reflects sunlight directly and the gases glow from ionisation . Most comets are too faint to be visible without the aid of a telescope , but a few each decade become bright enough to be visible to the naked eye . </P>
when does a comet have the longest tail and largest coma
when does a comet have the longest tail and largest coma
when a comet passes through the inner Solar System
when a comet passes through the inner Solar System