An infrared telescope is a

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observ ...

that uses

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

light to detect celestial bodies. Infrared light is one of several types of radiation present in the

electromagnetic spectrum The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging fro ...

. All celestial objects with a temperature above absolute zero emit some form of

electromagnetic radiation In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) li ...

. In order to study the universe, scientists use several different types of telescopes to detect these different types of emitted radiation in the electromagnetic spectrum. Some of these are

gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically ...

x-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

ultra-violet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiatio ...

, regular

visible light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...

(optical), as well as infrared telescopes.

Leading discoveries

There were several key developments that led to the invention of the infrared telescope: * In 1800,

William Herschel Frederick William Herschel (; german: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Caroline ...

discovered infrared radiation. * In 1878, Samuel Pierpoint Langley created the first

bolometer A bolometer is a device for measuring radiant heat by means of a material having a temperature-dependent electrical resistance. It was invented in 1878 by the American astronomer Samuel Pierpont Langley. Principle of operation A bolometer ...

. This was a very sensitive instrument that could electrically detect incredibly small changes in temperature in the infrared spectrum. * Thomas Edison used an alternative technology, his

tasimeter The tasimeter, or microtasimeter, or ''measurer of infinitesimal pressure'', is a device designed by Thomas Edison to measure infrared radiation. In 1878, Samuel Langley, Henry Draper, and other American scientists needed a highly sensitive in ...

, to measure heat in the sun's

corona Corona (from the Latin for 'crown') most commonly refers to: * Stellar corona, the outer atmosphere of the Sun or another star * Corona (beer), a Mexican beer * Corona, informal term for the coronavirus SARS-CoV-2, which causes the COVID-19 di ...

during the

solar eclipse of July 29, 1878 A total solar eclipse occurred on July 29, 1878, over much of North America including the region of the Rocky Mountains. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the ...

. * In the 1950s, scientists used lead-sulfide detectors to detect the infrared radiation from space. These detectors were cooled with liquid nitrogen. * Between 1959 and 1961, Harold Johnson created near-infrared

photometer A photometer is an instrument that measures the strength of electromagnetic radiation in the range from ultraviolet to infrared and including the visible spectrum. Most photometers convert light into an electric current using a photoresistor, ...

s which allowed scientists to measure thousands of stars. * In 1961, Frank Low invented the first germanium bolometer. This invention, cooled by

liquid helium Liquid helium is a physical state of helium at very low temperatures at standard atmospheric pressures. Liquid helium may show superfluidity. At standard pressure, the chemical element helium exists in a liquid form only at the extremely low temp ...

, led the way for current infrared telescope development.Timeline
Caltech Infrared telescopes may be ground-based, air-borne, or

space telescope A space telescope or space observatory is a telescope in outer space used to observe astronomical objects. Suggested by Lyman Spitzer in 1946, the first operational telescopes were the American Orbiting Astronomical Observatory, OAO-2 launch ...

s. They contain an infrared camera with a special solid-state infrared detector which must be cooled to cryogenic temperatures. Ground-based telescopes were the first to be used to observe outer space in infrared. Their popularity increased in the mid-1960s. Ground-based telescopes have limitations because

water vapor (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous p ...

in the Earth's atmosphere absorbs infrared radiation. Ground-based infrared telescopes tend to be placed on high mountains and in very dry climates to improve visibility. In the 1960s, scientists used balloons to lift infrared telescopes to higher altitudes. With balloons, they were able to reach about up. In 1967, infrared telescopes were placed on rockets. These were the first air-borne infrared telescopes. Since then, aircraft like the

Kuiper Airborne Observatory The Gerard P. Kuiper Airborne Observatory (KAO) was a national facility operated by NASA to support research in infrared astronomy. The observation platform was a highly modified Lockheed C-141A Starlifter jet transport aircraft (s/n: 6110, reg ...

(KAO) have been adapted to carry infrared telescopes. A more recent air-borne infrared telescope to reach the stratosphere was NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA) in May 2010. Together, United States scientists and the German Aerospace Center scientists placed a 17-ton infrared telescope on a Boeing 747 jet airplane. Placing infrared telescopes in space completely eliminates the interference from the Earth's atmosphere. One of the most significant infrared telescope projects was the

Infrared Astronomical Satellite The Infrared Astronomical Satellite (Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a survey of the entire night sky at infrared wavelengths. Launched on 25 January 1983, its mission lasted ten mon ...

(IRAS) that launched in 1983. It revealed information about other galaxies, as well as information about the center of our galaxy the Milky Way. NASA presently has solar-powered spacecraft in space with an infrared telescope called the

Wide-field Infrared Survey Explorer Wide-field Infrared Survey Explorer (WISE, observatory code C51, Explorer 92 and SMEX-6) is a NASA infrared astronomy space telescope in the Explorers Program. It was launched in December 2009, and placed in hibernation mode in February 201 ...

(WISE). It was launched on December 14, 2009.Griggs, B. (2009, December 14) NASA launches infrared telescope to scan entire sky. ''Cable News Network''. Retrieved from http://www.cnn.com/2009/TECH/space/12/14/wise.spacecraft.launch/index.html

Selective comparison

The wavelength of visible light is about 0.4 μm to 0.7 μm, and 0.75 μm to 1000 μm (1 mm) is a typical range for

infrared astronomy Infrared astronomy is a sub-discipline of astronomy which specializes in the observation and analysis of astronomical objects using infrared (IR) radiation. The wavelength of infrared light ranges from 0.75 to 300 micrometers, and falls in betw ...

far-infrared astronomy Far-infrared astronomy is the branch of astronomy and astrophysics that deals with objects visible in far-infrared radiation (extending from 30 μm towards submillimeter wavelengths around 450 μm). In the far-infrared, stars are not espec ...

, to

submillimetre astronomy Submillimetre astronomy or submillimeter astronomy (see spelling differences) is the branch of observational astronomy that is conducted at submillimetre wavelengths (i.e., terahertz radiation) of the electromagnetic spectrum. Astronomers pla ...

Infrared telescopes

Ground based : * Infrared Telescope Facility, Hawaii, 1979– *

Gornergrat Infrared Telescope The Telescopio InfraRosso del Gornergrat (TIRGO), or the Gornergrat Infrared Telescope, was located on the northern tower of the Kulm Hotel at Gornergrat ( altitude) near Zermatt, Switzerland. It was a Cassegrain telescope with a tip-tilt corre ...

, 1979–2005 *

Infrared Optical Telescope Array The Infrared Optical Telescope Array (IOTA) was a stellar interferometer array. IOTA began with an agreement in 1988 among five Institutions, the Smithsonian Astrophysical Observatory, Harvard University, the University of Massachusetts Amherst, t ...

, 1988–2006 *

United Kingdom Infrared Telescope The United Kingdom Infra-Red Telescope (UKIRT) is a 3.8 metre (150 inch) infrared reflecting telescope, the second largest dedicated infrared (1 to 30 micrometres) telescope in the world. It is located on Mauna Kea, Hawai'i as part of Mauna ...

, 1979– *

Wyoming Infrared Observatory The Wyoming Infrared Observatory (WIRO) is an astronomical observatory owned and operated by the University of Wyoming. It is located on Jelm Mountain, southwest of Laramie, Wyoming, U.S. It was founded in 1975, and observations began at the ...

, 1977- Airborne: *

(KAO), 1974-1995 * Stratospheric Observatory for Infrared Astronomy (SOFIA), 2010-2022 Space based: *

, 1983 * Spitzer Space Telescope, 2003-2020 * Herschel Space Observatory, 2009-2013 *

(WISE), 2009- *

Nancy Grace Roman Space Telescope The Nancy Grace Roman Space Telescope (shortened as Roman or the Roman Space Telescope, and formerly the Wide-Field Infrared Survey Telescope or WFIRST) is a NASA infrared space telescope currently in development and scheduled to launch by Ma ...

(formerly WFIRST) * James Webb Space Telescope (JWST), 2021-

Notes

{{Portal bar, Astronomy, Stars, Spaceflight, Outer space, Solar System Telescope types Infrared imaging

Leading discoveries

Selective comparison

Infrared telescopes

See also

Notes