Asterismen

An asterism is a recognizable pattern of stars in the night sky, seen by observers and used for navigation and orientation. Unlike constellations, which are official areas of the sky defined by the International Astronomical Union, asterisms are informal patterns that may lie within a single constellation or span across several constellations. The term derives from the Greek asterisma, meaning "a starry thing" or "star arrangement."

Several well-known asterisms help stargazers find their bearings. The Big Dipper (the Plough) is an asterism in the constellation Ursa Major, formed by seven bright stars whose outer edge points to Polaris. The Summer Triangle is a prominent three-star pattern formed by Vega (in Lyra), Deneb (in Cygnus), and Altair (in Aquila); it crosses three constellations. The Great Square of Pegasus is a large square of four stars in the Pegasus region, used as a navigation aid in autumn skies. The Teapot is an asterism in Sagittarius, recognizable by its shape resembling a teapot. The Winter Triangle consists of the bright stars Betelgeuse, Sirius, and Procyon, spanning Orion and Canis Major/Minor. In southern skies, the Southern Cross is a famous asterism formed by four bright stars within Crux and is used for orientation in the southern hemisphere.

Asterisms are informal and not standardized; they vary by culture and era, and may be partially or wholly contained within one or more official constellations. They remain a useful aid for observation, education, and historical navigation.