Infrared astronomy is the branch of astronomy and astrophysics which deals with objects visible in infrared (IR) radiation. Visible radiation ranges from 400nm (blue) to 700nm (red). Longer wavelengths than 700nm but still shorter than microwaves are called infrared.


After the use of prisms by Isaac Newton to split white light into a spectrum, it was found in 1800 that the hottest part of the band of light from the sun was actually past the red end of the spectrum. These "heat rays" even displayed some spectral lines.

Since then, like all other forms of electromagnetic radiation, infrared was utilised by astronomers to learn more about the universe. As infrared is esentially heat radiation, infrared telescopes (which are practically the same as optical telescopes) need to be shielded from heat and chilled with liquid nitrogen in order to actually form images. For this reason many infrared telescopes are built in the Antarctic region where conditions are as good as possible on Earth.

However, as with optical telescopes, space is the most ideal place for their use and most telescopes planned to be sent into space will be optimised for infrared applications.