Part of spectrum viewed: Infrared (wavelengths longer than visible light).
Location: In orbit, as most infrared is blocked by the atmosphere.
Sources of radiation:
- Stars give off infrared as well as visible light.
- Cool stars give off more infrared than visible light.
- Dust that has been heated gives off infrared.
- Infrared can pass through dust clouds.
Image: The Milky Way imaged by Spitzer. This infrared image shows what cannot be seen in visible light – cooler stars (blue), heated dust (reddish hue) and Sagittarius A-Star as a bright white spot in the middle. Image by NASA/JPL-Caltech/S. Stolovy (Spitzer Science Center/Caltech) and released into the public domain.