Halo stars

Halo stars. These have much larger orbits which carry them up far from the galaxy’s disk.

The term Halo Star stems from the fact that these stars populate the Galactic Halo.

The Milky Way's stellar halo contains globular clusters, RR Lyrae stars with low metal content, and subdwarfs. Stars in our stellar halo tend to be old (most are greater than 12 billion years old) and metal-poor, but there are also halo star clusters with observed metal content similar to disk stars. The halo stars of the Milky Way have an observed radial velocity dispersion of about 200 km/s and a low average velocity of rotation of about 50 km/s. Star formation in the stellar halo of the Milky Way ceased long ago.

[1]A galactic halo is an extended, roughly spherical component of a galaxy which extends beyond the main, visible component.Several distinct components of galaxies comprise the halo: