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| a theory that deduces a cataclysmic birth of the universe from the observed expansion of the universe, cosmic background radiation, abundance of the elements, and the laws of physics |
| a system of two stars that revolve about a common center of mass |
| Main Entry: | open cluster |
| Part of Speech: | n |
| Definition: | a loose grouping of stars |
| Usage: | astronomy |
| open cluster
A loose, irregular grouping of stars that originated from a single nebula in the arms of a spiral galaxy. Compared to globular clusters, open clusters generally contain younger and fewer (from a hundred to several thousand) stars and are confined to the disk of the galaxy. Because they are young, open clusters are sometimes still surrounded by the leftover gas and dust from which they formed. Visible from Earth with just a pair of binoculars and containing over 3,000 stars, the Pleiades is the best known open cluster. Also called galactic cluster. Compare globular cluster. |