The term "stellar halo" refers to a roughly spherical region surrounding a galaxy, composed of stars, globular clusters, and dark matter. The stellar halo typically contains older stars and is less dense than the main disk of the galaxy. In our Milky Way, for instance, the stellar halo extends well beyond the visible disk and is thought to be a remnant of the early stages of galaxy formation and accretion of smaller galaxies and star clusters.
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