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A stellar halo consists of a lesser density of stars (halo stars) surrounding a galaxy, comprising one aspect of its galactic halo. Their region also likely includes globular clusters and often the term stellar halo is meant to include them. I believe the term generally is not meant to include satellite galaxies within the region (which can include star formation), but it does include stars presumed to be from past/destroyed satellite galaxies, such as stellar streams. The Milky Way's stellar halo extends nearly an order-of-magnitude further than its clearly-visible disk, and contains possibly as much as a percent of the stars. The halo stars are generally old and of very low metallicity, as are the halo globular clusters.