Comet
Also called: coma, tail, nucleus.
A small icy body that grows a glowing head (coma) and tails when it nears the Sun.
A comet's nucleus is a few kilometres of ice and dust. As it nears the Sun the ice turns to gas, making a fuzzy coma and tails pushed away from the Sun: a curved dust tail and a straight, bluish ion tail. Most comets are telescopic smudges; a bright naked-eye comet comes along every few years.
At the eyepiece
Comets look like fuzzy stars that move slowly against the background over a night. Low power and a dark sky show the tail best.
In AstroPilot
Tonight lists comets within reach, with positions from NASA/JPL.