infrared astronomy

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The branch of astronomy that uses observations of emissions in the infrared part of the electromagnetic spectrum to study extraterrestrial sources such as stars, planets, galaxies, and interstellar gas and dust clouds.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun astronomy the astronomical observation and study of objects, cooler than most stars, using the infrared part of the electromagnetic spectrum