Comets

Comets

Comets are large icy snowballs that orbit in the solar system, passing between the planets.
Each comet began as one of the hundreds of billions of small bodies in an immense cloud surrounding the sun, far beyond the outermost planets. Sometimes a gravitational "touch" from a passing star causes one of these bodies to move closer to the sun. Solar energy from the sun heats up the body, which produces gas and dust that form a tail. The gas is then pushed away leaving another tail which is why some comets have two visible tails.
Near the sun a comet can change drastically in size and shape; it may even split into two or more pieces. [VH] {SR} {EP}