This view of the Andromeda galaxy from the Herschel space observatory shows relatively cool lanes of forming stars. Herschel was sensitive to the far-infrared light from cool dust mixed in with the gas where stars are born. This image reveals some of the very coldest dust in the galaxy (colored red here) that is only a few tens of degrees above absolute zero. Warmer regions such as the densely populated central bulge, home to older stars, appear as blue. Star-formation zones are in the spiral arms with several concentric rings interspersed with dark gaps where star formation is absent.
Andromeda (aka M31) is the nearest major galaxy to our own Milky Way about 2.5 million light-years away. Herschel was a European Space Agency mission active from 2009 to 2013.
Image Credit: ESA