A star is a gaseous self-luminous body in space. A man can see between 3000 and 4,000 stars on a clear night. In general, a star's brightness depends upon its distance from us, its temperature and its size. The smallest known stars are about the size of planets. The largest stars are hundreds of times the diameter of the Sun. The colours most often seen in the stars are red, orange, yellow, white and blue. There are some violet and a few green stars.