M33, the Triangulum Galaxy, is a favorite of astronomers, amateur and professional alike, because of its orientation and relative proximity to us. It is the second nearest spiral galaxy to our Milky Way (after M31, the Andromeda Galaxy) and a part of the “local group” of galaxies. From our perspective, M33’s disk appears at moderate inclination. That permits us to see its internal structure clearly. M31 is oriented nearly edge-on.
The Galaxy Evolution Explorer took this picture of M33 in ultraviolet wavelengths. Ultraviolet imaging mostly shows us emissions from the atmospheres of hot, young stars. Young in this case means only a few hundred million years old. Observations of M33 allow astronomers to compare the population of young, massive stars with other components of the galaxy such as interstellar dust and gas. The clouds contain the raw material from which stars form. This comparison gives us insight into the star formation process as it occurs throughout an entire spiral galaxy and is an important resource for studies of galaxy evolution.
Image Credit: NASA