Andromeda Galaxy (M31), ultraviolet image from the GALEX satellite. Two regions of the ultraviolet (UV) spectrum were examined, the far (FUV) and the near (NUV) regions. FUV (blue) is from the young, bright stars in the galaxys spiral arms. The NUV emissions (orange) show the older stars in the galaxys centre, as well as foreground stars from the Milky Way. M31 is the nearest large galaxy to our own. It is 150,000 light years across and 2.2 million light years distant. Image data obtained in 2003. The GALEX (Galaxy Evolution Explorer) satellite is designed to use UV sensors to study the evolution of galaxies.
