The Electromagnetic Spectrum Infrared observations reveal cool states of matter. Most of the energy radiated by objects in this temperature range lies in the infrared. Infrared observations are therefore of particular importance in studying low-temperature environments such as dusty interstellar clouds where stars are forming and the icy surfaces of planetary satellites and asteroids. Infrared observations explore the hidden Universe. Cosmic dust particles effectively obscure parts of the visible Universe and block our view of many critical astronomical environments.
Infrared observations access a wealth of spectral features.
Emission and absorption bands of virtually all molecules and solids lie in the infrared, where they can be used to probe conditions in cool celestial environments. Many atoms and ions have spectral features in the infrared which can be used for diagnostic studies of stellar atmospheres and interstellar gas, exploring regions which are too cool or too dust-enshrouded to be reached with optical observations. Infrared observations reach back to the early life of the cosmos. The cosmic redshift which results from the general expansion of the Universe inexorably shifts energy to longer wavelengths in an amount proportional to the object's distance. Because of the finite speed of light, objects at high redshift are observed as they were when the Universe and the objects were much younger.