The Great Galaxy in Andromeda (also known as Messier 31, or M31)
is the nearest large galaxy to our own Milky Way. New mid-infrared observations
made with the Infrared Array Camera (IRAC) and the Multiband
Imaging Photometer for Spitzer (MIPS) aboard the Spitzer Space Telescope
show that M31 looks dramatically different in the infrared
than it does at visible wavelengths. As the image at right shows,
its appearance is different even in the 4 mid-infrared bands of IRAC.
The mid-infrared data have made it possible to measure
precisely the structure of Messier 31 -- including the dramatic rings seen quite
clearly at 8 microns -- and its star formation rate.
Hectospec Studies of Stars, Clusters HII regions and PNe in M31
Dusty Waves on a Starry Sea: The Mid-Infrared View of M31
An almost head-on collision as the origin of two off-centre rings in the Andromeda galaxy .pdf
Spitzer MIPS Infrared Imaging of M31: Further Evidence for a Spiral-Ring Composite Structure .pdf
Infrared Array Camera on the Spitzer Space Telescope