A star is a large ball of hot gas, thousands to millions of kilometers in diameter, emitting large amounts of radiant energy from nuclear reactions in its interior. differ fundamentally from planets in that they are self-luminous, whereas planets shine by reflected sunlight. Except for the SUN, which is the nearest star, stars appear only as points of light, even in the largest telescopes, because of their distance. The brightest stars have long been given names. Most of the familiar names originated with the ancient Greeks or with late ....