Asterisms are prominent groups of bright stars to which the eye is drawn.
An example is the Big Dipper, which is part of a larger area of the sky called Ursa Major , a constellation . Constellations are often named for prominent groups of stars within them that represent a person, animal, or legendary creature from ancient mythology. Ptolemy listed 48 constellations in The Almagest , all of them still in use today. Since then, an additional 40 constellations have been identified so the celestial sphere is now divided into a total of 88 constellations. The boundaries of these 88 constellations were established by international agreement in 1930.