globular cluster

Astron.

a comparatively older, spherically symmetrical, compact group of up to a million old stars, held together by mutual gravitation, that are located in the galactic halo and move in giant and highly eccentric orbits around the galactic center.

Cf. open cluster, stellar association.

[1855-60]

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Any large group of old, Population II (see Populations I and II) stars closely packed in a symmetrical, somewhat spherical form.

About 150 have been identified in the Milky Way Galaxy. Most are distributed in a spherical volume above and below the Galaxy's disk (see galactic halo). Globular clusters contain many more stars (10,000–1,000,000) than open clusters do and can be several hundred light-years in diameter. Because they are so distant from the solar system, most are not visible to the unaided eye. Omega Centauri and a few others can be seen without a telescope as hazy patches of light.

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      any large group of old stars that are closely packed in a symmetrical, somewhat spherical form. See star cluster.

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