Halo

Definition

A halo is a roughly spherical region surrounding the Milky Way Galaxy that contains older stars, globular clusters, and dark matter. It is not as dense as other parts of the galaxy and extends beyond the visible disk.

5 Must Know Facts For Your Next Test

1. The halo contains a majority of the galaxy's dark matter.
2. Stars in the halo are typically older and have lower metallicity than those in the galactic disk.
3. Globular clusters are densely packed groups of old stars found within the halo.
4. The halo can be subdivided into an inner and outer region, with different characteristics such as stellar density and composition.
5. It extends well beyond the visible part of the Milky Way, influencing its gravitational pull.

Review Questions

• What type of stars are predominantly found in the Milky Way's halo?
• How does the metallicity of stars in the halo compare to those in the galactic disk?
• What role does dark matter play in the structure of the Milky Way's halo?

Related terms

Globular Cluster: A spherical collection of old stars orbiting around a galaxy's core, often found in halos.

Dark Matter: A form of matter that does not emit light or energy but exerts gravitational forces, making up most of the mass in a galaxy's halo.

Galactic Disk: The flat, circular region of a galaxy containing most of its stars, gas, and dust.