Asterism (astronomy)

An asterism is an observed pattern or group of stars in the sky. Constellations are based on asterisms, but asterisms can be any pattern or group of stars. They are a more general concept than the 88 constellations of the IAU. Several countries use these patterns in their flags. 

The area of the southern cross is known as the constellation Crux. In this case the asterism and the constellation are more or less the same thing.

The Big Dipper, also known as The Plough, is made of the seven brightest stars in Ursa Major. It is certainly the best-known asterism in the Northern Hemisphere.

Category:Stars