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NASA Spitzer Space Telescope • Jet Propulsion Laboratory
• California Institute of Technology
• Vision for Space Exploration
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What Is Infrared?

Infrared (IR) is a form of light (or radiation) that is invisible to the human eye. It is the portion of the electromagnetic spectrum found between visible light and radio waves, at wavelengths extending from 1 to 200 microns. [A micron is one-millionth of a meter, and is abbreviated as µm.]

Infrared is part of the electromagnetic spectrum.

Astronomers often refer to different types of infrared light, although the precise wavelength ranges are somewhat arbitrary. For the most part, infrared light is thermal radiation; that is, it is a measure of heat. Cooler objects emit IR light at longer wavelengths.

More Information



The Spitzer Space Telescope is a NASA mission managed by the Jet Propulsion Laboratory. This website is maintained by the Spitzer Science Center, located on the campus of the California Institute of Technology and part of NASA's Infrared Processing and Analysis Center. Privacy Policy

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