Asterism

An asterism is a recognizable pattern of stars that is not itself one of the 88 officially defined constellations. Its stars may belong to one or several constellations.

Big Dipper: A seven-star pattern forming the hindquarters and tail of Ursa Major. It is a prominent asterism contained within a larger constellation.
Constellation: One of 88 officially defined regions of the celestial sphere, often associated with a traditional star pattern. An asterism is a pattern, whereas a constellation is an officially bounded region.
Asterism (astronomy): A pattern of celestial objects recognized by observers, including patterns made from stars or other objects. The star-pattern sense of asterism belongs to this broader astronomical usage.
Ursa Major: A large northern constellation containing the Big Dipper asterism. The Big Dipper is a familiar pattern within this constellation.
Little Dipper: A seven-star pattern forming the main outline of Ursa Minor. It is an asterism that nearly traces its constellation's shape.
Celestial sphere: An imaginary sphere surrounding Earth onto which celestial objects appear projected. Constellation boundaries divide the sky represented by this sphere.
Line of sight: The straight path along which an observer sees a distant object. Stars at different distances can appear grouped when their directions nearly coincide.
Ursa Minor: A northern constellation containing Polaris and the Little Dipper asterism. The Little Dipper provides a recognizable outline within this constellation.
Summer Triangle: A large asterism formed by Vega, Deneb, and Altair. Its three bright stars span three separate constellations.
International Astronomical Union: An international organization of professional astronomers that coordinates astronomical nomenclature and standards. It formally recognized the 88 constellations and their boundaries.

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