A star is a massive luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The most prominent starts on the celestial sphere were grouped together into constellations and asterisms, and the brightest starts gained proper names. Extensive catalogues of stars have been assembled by astronomers, which provide standardized star designations. Astronomers can determine the mass, age, chemical composition and many other properties of a star by observing its spectrum, luminosity, and motion through space. Binary and multi-star systems consist of two or more starts that are gravitationally bound, and generally move around each other in stable orbits. Historically, stars have been important to civilizations throughout the world. They have been part of religious practices and used for celestial navigation and orientation. The oldest accurately dated star chart appeared in ancient Egyptian astronomy in 1534 B.C.
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