Saturday, September 12, 2009

Dwarf Spheroidal Galaxy

A dwarf spheroidal galaxy is a low luminosity type of galaxy which is found as a satellite galaxy of the Milky Way and the Andromeda Galaxy M31. It is spheroidal in shape, lower luminosity, and similar to dwarf elliptical galaxies in appearance and properties such as little to no gas or dust. Dwarf spheroidal galaxies belong to the Local Group. Up until 2005, there were nine dwarf spheroidal galaxies in the Local Group, but the Sloan Digital Sky Survey has discovered eleven more. These types of galaxies might be the most common galaxies in the universe.

A dwarf spheroidal galaxy has extremely large amounts of dark matter. In the past, most astronomers believed that a dwarf spheroidal galaxy was merely a large, low density globular cluster. Nevertheless detailed studies in the last 20 years have revealed that the dwarf spheroidal galaxies have a more diverse set of properties and contain more complex stellar populations than the globular cluster analogy would predict.