comet

As a noun comet

is (astronomy) a celestial body consisting mainly of ice, dust and gas in a (usually very eccentric) orbit around the sun and having a "tail" of matter blown back from it by the solar wind as it approaches the sun.

As a verb skywatch is

to watch the sky for aircraft, satellites or ufos or for stars, comets etc.

In astronomy terms the difference between comet and chiron

is that comet is a celestial body consisting mainly of ice, dust and gas in a (usually very eccentric) orbit around the Sun and having a "tail" of matter blown back from it by the solar wind as it approaches the Sun while chiron is a centaur (minor planet) and comet-like object, orbiting between Saturn and Uranus.

As a noun comet

is a celestial body consisting mainly of ice, dust and gas in a (usually very eccentric) orbit around the Sun and having a "tail" of matter blown back from it by the solar wind as it approaches the Sun.

As a proper noun Chiron is

an old, wise centaur who served as Achilles' mentor and teacher.

As a noun comet

is (astronomy) a celestial body consisting mainly of ice, dust and gas in a (usually very eccentric) orbit around the sun and having a "tail" of matter blown back from it by the solar wind as it approaches the sun.

As an adjective cometesimal is

of, pertaining to or caused by a comet.