All celestial objects with a temperature above absolute zero

Absolute zero

Absolute zero is the theoretical temperature at which entropy reaches its minimum value. The laws of thermodynamics state that absolute zero cannot be reached using only thermodynamic means....

 emit some form of electromagnetic radiation

Electromagnetic radiation

Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...

. http://www.jpl.nasa.gov/news/press_kits/sirtflaunch.pdf 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

Gamma ray

Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...

, x-ray

X-ray

X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...

, ultra-violet, regular visible light (optical), as well as infrared telescopes.

Discoveries Leading to the Invention of the Infrared Telescope

In 1800, William Herschel

William Herschel

Sir Frederick William Herschel, KH, FRS, German: Friedrich Wilhelm Herschel was a German-born British astronomer, technical expert, and composer. Born in Hanover, Wilhelm first followed his father into the Military Band of Hanover, but emigrated to Britain at age 19...

 discovered infrared radiation.

In 1878, Samuel Pierpoint Langley created the first bolometer

Bolometer

A bolometer is a device for measuring the power of incident electromagnetic radiation via the heating of a material with a temperature-dependent electrical resistance. It was invented in 1878 by the American astronomer Samuel Pierpont Langley...

. This was a very sensitive instrument that could

electrically detect incredibly small changes in temperature in the infrared spectrum.

In the 1950s, scientists used lead-sulfide detectors to detect the infrared radiation from space. These detectors were

cooled with liquid nitrogen

Liquid nitrogen

Liquid nitrogen is nitrogen in a liquid state at a very low temperature. It is produced industrially by fractional distillation of liquid air. Liquid nitrogen is a colourless clear liquid with density of 0.807 g/mL at its boiling point and a dielectric constant of 1.4...

.

Between 1959 and 1961, Harold Johnson

Harold Johnson

Harold Johnson may refer to:*Harold Johnson , professional boxer*Harold Keith Johnson , American general*Harold Johnson , American astronomer*Harold T...

 created near-infrared photometer

Photometer

In its widest sense, a photometer is an instrument for measuring light intensity or optical properties of solutions or surfaces. Photometers are used to measure:*Illuminance*Irradiance*Light absorption*Scattering of light*Reflection of light*Fluorescence...

s which allowed scientists to measure thousands of stars.

In 1961, Frank Low invented the first germanium

Germanium

Germanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. The isolated element is a semiconductor, with an appearance most similar to elemental silicon....

 bolometer. This invention, cooled by liquid helium

Liquid helium

Helium exists in liquid form only at extremely low temperatures. The boiling point and critical point depend on the isotope of the helium; see the table below for values. The density of liquid helium-4 at its boiling point and 1 atmosphere is approximately 0.125 g/mL Helium-4 was first liquefied...

, led the way for current infrared telescope development. http://www.ipac.caltech.edu/Outreach/Edu/Timeline/timeline2.html

The three different types of infrared telescopes are ground-based telescopes, air-borne telescopes, and space telescopes. All three types of telescopes contain an infrared camera that must be cooled to hundreds of degrees below zero as well as a special solid-state infrared detector. http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ask_astronomer/faq/obs.shtml

Ground-based telescopes were the first type of infrared telescopes to be used to observe outer space. Their popularity increased in the mid-1960s. Ground-based telescopes have limitations because water vapor 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 25 miles up. In 1967, infrared telescopes were placed on rockets. http://www.ipac.caltech.edu/Outreach/Edu/Timeline/timeline2.html These were the first air-borne infrared telescopes. A more recent air-borne infrared telescope to reach the stratosphere was NASA's Stratospheric Observatory for Infrared Astronomy

Stratospheric Observatory for Infrared Astronomy

The Stratospheric Observatory for Infrared Astronomy is a joint project of NASA and the German Aerospace Center to construct and maintain an airborne observatory. NASA awarded the contract for the development of the aircraft, operation of the observatory and management of the American part of the...

 (SOFIA) in May of 2010. Together, United States scientists and the German Aerospace Center scientists placed a 17 ton infrared telescope on a Boeing 747

Boeing 747

The Boeing 747 is a wide-body commercial airliner and cargo transport, often referred to by its original nickname, Jumbo Jet, or Queen of the Skies. It is among the world's most recognizable aircraft, and was the first wide-body ever produced...

 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 (IRAS) that launched in 1983. It revealed information about other galaxies, as well as information about the center of our galaxy the Milky Way. http://www.ipac.caltech.edu/Outreach/Edu/Timeline/timeline2.html NASA presently has solar-powered spacecraft in space with an infrared telescope called the Wide-field Infrared Survey Explorer

Wide-field Infrared Survey Explorer

Wide-field Infrared Survey Explorer is a NASA infrared-wavelength astronomical space telescope launched on December 14, 2009, and decommissioned/hibernated on February 17, 2011 when its transmitter was turned off...

 (WISE). It was launched on December 14th in 2009.

Selective comparison

Existing infrared telescopes

• Infrared Telescope Facility
  Infrared Telescope Facility
  The NASA Infrared Telescope Facility is a telescope optimized for use in infrared astronomy and located at the Mauna Kea Observatory in Hawai'i. It was first built to support the Voyager missions and is now the USA national facility for infrared astronomy, providing continued support to...
  
  , 1979-
• Gornergrat Infrared Telescope
  Gornergrat Infrared Telescope
  The Telescopio InfraRosso del Gornergrat is located on the northern tower of the Kulm Hotel at Gornergrat near Zermatt, Switzerland. It was a Cassegrain telescope with a tip-tilt correcting secondary and optimized for infrared observations, but was decommissioned in March 2005...
  
  , 1979–2005
• Infrared Optical Telescope Array
  Infrared Optical Telescope Array
  The Infrared Optical Telescope Array began with an agreement in 1988 among five Institutions, the Smithsonian Astrophysical Observatory, Harvard University, the University of Massachusetts, the University of Wyoming, and MIT/Lincoln Laboratory, to build a two-telescope stellar interferometer for...
  
  , 1988–2006
• United Kingdom Infrared Telescope
  United Kingdom Infrared Telescope
  UKIRT, the United Kingdom Infra-Red Telescope, is a 3.8 metre infrared reflecting telescope, the largest dedicated infrared telescope in the world. It is operated by the Joint Astronomy Centre in Hilo and located on Mauna Kea, Hawai'i as part of Mauna Kea Observatory...
  
  , 1979-
• Spitzer Space Telescope
  Spitzer Space Telescope
  The Spitzer Space Telescope , formerly the Space Infrared Telescope Facility is an infrared space observatory launched in 2003...
  
  , 2003

See also

• Infrared astronomy
  Infrared astronomy
  Infrared astronomy is the branch of astronomy and astrophysics that studies astronomical objects visible in infrared radiation. The wavelength of infrared light ranges from 0.75 to 300 micrometers...
  
  
• List of largest infrared telescopes
• List of telescope types