A bright comet can be a spectacular sight, moving slowly against the background stars, it seems to hang in the sky like a ghostly sword for days or weeks. A head of a comet is called a nucleus. The gas that evaprorates forms a cloud called the coma that is the ball at the front of the comet you see in the night sky when you are looking at a comet. People long ago thought that comets were stars growing hair. Some comets orbit around the sun every few years while others may come around only every hundred years like for instance Haileys comet comes around every eighty-six years.
Some comets tails are more than millions of miles long.
A comet usually has two tails, the gas tail which is usually smaller and the dust tail.