(via APOD: 2013 February 2 - Herschel’s Andromeda)
Image Credit: ESA/Herschel/PACS & SPIRE Consortium, O. Krause, HSC, H. Linz
Herschel Space Observatory is the ESA’s amazing infrared telescope. Like NASA’s Spitzer Space Telescope, it is capable of seeing cooler (literally, as in lower temperatures) things in the universe. In this case, the dust lanes of our Local Group partner, M31, the Andromeda Galaxy. The redder material in the outskirts is quite cool, barely warmed above absolute zero by the sparse numbers of stars, while the blues in the center show hot dust energized by the crowd of stars in the core of the galaxy.
The dust itself can be used to trace molecular gas as well (both are usually found together in cool clouds) and show how much star formation is possible in Andromeda. These clouds of gas and dust tend to get shocked by supernovae or passing stars and start condensing and collapsing to form new generations of stars.