An Etymological Dictionary of Astronomy and Astrophysics
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The largest and most luminous → globular cluster associated with the Milky Way Galaxy. Omega Centauri is located about 18,300 → light-years away and contains several million old stars. The stars in its center are so crowded that they are believed to be only 0.1 light-year away from each other. It is about 12 billion years old. Omega Centauri was first listed in Ptolemy's catalog nearly two thousand years ago. In 1677 Edmond Halley reported it as a nebula, and in the 1830s John Herschel was the first to correctly identify it as a globular cluster. Also called NGC 5139.

Omega, Gk. alphabet letter; Centauri, → Centaurus.