What is the difference between a galactic bulge and halo?

A galaxy is an immense, gravitationally-bound system of stars, gas, dust, and dark matter. Our own Milky Way galaxy, for example, is a barred spiral galaxy that contains billions of stars and other celestial objects. Within the Milky Way, there are distinct regions that astronomers refer to as the galactic bulge and the galactic halo.

The galactic bulge is a dense, spheroidal region at the center of the Milky Way that is made up of older stars. The bulge is roughly 10,000 light-years in diameter and has a mass equivalent to about 20 billion suns. The galactic halo, on the other hand, is a roughly spherical distribution of stars, globular clusters, and dark matter that surrounds the entire galaxy. The halo is much larger than the bulge and extends to distances of over 100,000 light-years from the center of the galaxy.

One of the main differences between the galactic bulge and the halo is their structure and composition. While the bulge is dense and contains mostly older stars, the halo is more diffuse and contains a mix of older and younger stars. The halo also contains many globular clusters, which are groups of stars that formed at roughly the same time and are gravitationally bound to one another.