asterisma

Asterisma, more commonly referred to in English as an asterism, is a recognizable pattern of stars in the night sky that forms a shape or outline. Unlike constellations, which are officially defined areas of the sky, an asterism is a is a human-made pattern derived from the arrangement of stars as seen from Earth. The spelling asterisma appears in some writings and in non-English contexts, but asterism is the standard term in modern astronomy.

Examples of well-known asterisms include the Big Dipper (the seven-star pattern within Ursa Major), the Summer Triangle (Vega, Deneb, and Altair), Orion’s Belt (three aligned stars in Orion), and Cassiopeia’s distinctive W shape. The Teapot asterism in the constellation Sagittarius is another popular example used in star-hopping to locate the Galactic center and surrounding stars. Asterisms can cross constellation boundaries and are often emphasized in star charts and educational materials because they are easier to recognize than formal constellations.

Uses and significance include aiding star-hopping for navigation and observational astronomy, as well as serving as a bridge between professional astronomy and public instruction. Cultural variations exist in which asterisms are recognized and how they are named. Etymologically, the term derives from Latin asterismus, ultimately from Greek, reflecting its roots in describing “little stars.”