This infrared composite from NASA's Spitzer Space Telescope shows the neighboring Andromeda galaxy. It reveals choppy waves of dust (red) and a more tranquil sea of stars (blue). Because this galaxy is so large, the infrared images had to be stitched together out of about 3,000 separate Spitzer exposures. The light detected by Spitzer's infrared array camera at 3.6 microns is sensitive mostly to starlight and is shown in blue. The 8-micron light shows warm dust and is shown in red. The contribution from starlight has been subtracted from the 8-micron image to better highlight the dust structures.