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Links: Polyphonic Ringtones |
All objects in the universe radiate heat. The energy distribution of this radiation with wavelength is a function of the temperature of the source. The Sun, at a temperature of more than 5000 K, radiates primarily at visual wavelengths and appears yellow. Colder sources radiate at longer wavelengths. Thus, the heating element of an electric stove appears orange red. Objects in space, such as asteroids, comets, and planets, also radiate, but at wavelengths much longer than can be detected by the human eye. This region of the spectrum is referred to as the thermal infrared. Analysis of the thermal radiation from an object can tell us much about its composition and other physical properties. Observing this radiation from ground-based telescopes is complicated by thermal emission from the telescope itself and the atmosphere, which are much brighter than the astro-physical sources at which they are looking. This has been compared to observing a star in the daytime with the telescope on fire. |