constellation

A constellation is a set of stars in a region of the celestial sphere which people have decided form a group, typically named after an image that people find it resembles, of a person, animal, or object. Examples: Orion, Sagittarius, and Ursa Major. A constellation's stars are grouped by angular distance but this does not imply the stars are actually close to each other. For astronomy, a set of standardized constellations (modern constellations), generally based upon traditional constellations, are now used to refer to portions of the sky, i.e., 88 divisions of the sky defined by the International Astronomical Union (IAU). Names of objects (especially those viewable without a telescope) often reference the constellations that contain them, such as traditional stellar designations (Bayer designations and Flamsteed designations). Galaxy names often use them as well, e.g., Andromeda and Triangulum. Some of the constellation names, such as Orion, are commonly referred to in astrophysics when the constellation contains objects of study, such as prominent star-forming regions.