A stellar halo is a vast, spherical region surrounding a galaxy, filled with stars, gas, and dark matter. This area contains older stars that are often less bright than those found in the galaxy's main disk. The halo can extend far beyond the visible parts of the galaxy, giving it a ghostly appearance. In our own galaxy, the Milky Way, the stellar halo is home to globular clusters, which are tightly packed groups of stars. These clusters are some of the oldest objects in the universe, providing valuable insights into the early formation of galaxies and the evolution of the cosmos.