Omega Centauri: A Bright Old Star Cluster

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Omega Centauri is a round group of many stars. It has about 10 million stars. These stars are much older than the Sun. The group is about 150 light-years across. It is also called NGC 5139. It is 15,000 light-years away. It is the largest and brightest of about 200 such star groups in the halo of the Milky Way. Most star groups have stars that are the same age and the same chemicals. Omega Cen has stars of different ages and different chemicals. Omega Cen may be the old center of a small galaxy that is merging with the Milky Way. The cluster looks yellow. Its red giant stars are easy to see in a telescope. A twenty-year look with the Hubble Space Telescope found a big black hole near the center.

APOD's email for image submissions has changed. Please see APOD Submissions. APOD's main NASA site is moving. It will go from apod. nasa.gov to science. nasa.gov/ apod. Tomorrow's picture will show reflections on a starry night.