You cannot see the nucleus ( centre) of a comet with the naked eye but you can sometimes see its tail. It appears as a smear of light that very gradually moves across the sky. As a comet moves closer to the Sun, the ice and other frozen gases in its nucleus begin to boil off, producing a long tail of gas and dust. The tail will always point away from the Sun because light and other forms of radiation from the Sun push against the minute particles that are present within the tail. Comet tails are very different in shape and size. Some are short and stubby. Others are long and slender. As the tail grows, the comet gains in speed because it is nearing the Sun.
Halley’s Comet is perhaps the most famous comet of all. It can be seen from Earth every 76 years and was even recorded in 1066 on the Bayeux Tapestry.