Infrared Telescope

A telescope is defined as a combination of mirrors and lenses which gather visible light for observing distant bodies. Telescopes have been used to study celestial bodies. Infrared telescope can be defined as a telescope that uses infrared light to spot celestial bodies. Infrared light is electromagnetic radiation having wavelength shorter than a radio wave but longer as compared to visible light. It's interesting to know that all celestial bodies having temperature higher than absolute zero emit electromagnetic radiation. In addition to infrared radiation, scientists have been using optical telescope, gamma rays and ultra violet rays, to name a few technologies, to detect electromagnetic radiation emitted by celestial bodies.

The following are the facts related to infrared telescope, such as, discovery of Infrared light, types, applications and design.

History
Great inventors like William and Caroline Herschel have contributed a lot in Astronomy while the infrared radiation was discovered by William Herschel in 1800. In the Infrared spectrum, change in temperature could be detected by Bolometer, discovered by Samuel Pirepoint in 1878. Infrared radiation from space was first spotted by detectors discovered in mid 1050s. Bolometer created by Frank Low in 1961, was the breakthrough giving rise to today's infrared telescope.

Design
The working principle resembles the one of visible light telescope and the components are also the same. A combination of mirror and lens collect and converge radiation on a detector, made up of Mercury Cadmium Telluride or HgCdTe alloy. The data from the detector or a collection of detectors is interpreted by a computer for analysis. Helium or Liquid Nitrogen is used as a coolant, which keeps the temperature approximately equal to absolute zero. This prevents the detector from getting contaminated by heat sources. Telescope at Spitzer space is the largest ever built infrared telescope, which is cooled up to -273 ºC.

Types
It is categorized into 3 different types such as, Space Telescope, Air-borne Telescope and Ground Telescope. All the 3 types are equipped with an advanced infrared detector and Infrared camera and are kept cooled to a couple of hundred degrees below zero. Ground Telescopes were used first to detect celestial bodies. They started getting recognition in 1960s. The limitation in Ground Telescopes is due to the absorption of radiation by water vapor present in earth's atmosphere. Ground Telescopes were lifted to altitudes as high as 24 miles with the help of balloons, in 1960s. By late sixties, these telescopes started getting lodged in rockets, which was the first use of Air-borne Telescopes. SOPHIA or Stratospheric Observatory for Infrared Astronomy by NASA reached stratosphere in May of 2010. it was approximately 17.5 Ton Telescope lodged in an airplane. When stationed in space, it prevents interference by earth's atmosphere. In 1983, IRAS or Infrared Astronomical Satellite was launched, it disclosed the information about the center of milky way and other galaxies as well. WISE or Wide-field Infrared Survey Explorer, developed by NASA, is a spacecraft with Space Telescope, launched in 2009.

Applications
These devices have found applications in areas such as detection of nebulae, brown star astronomy and planets, which are extremely faint and cool and are difficult to be observed in visible light. As discussed above, Infrared radiation has larger wavelength as compared to visible light, making it penetrate through astronomical dust or gases without getting scattered. This makes one of the most important applications of these telescopes to observe milky way, which, if viewed in visible light, becomes obscured. Also, redshift phenomenon results in increasing the wavelength of celestial object as its distance from the earth increases. Hence, as the radiation from these bodies reach earth, it causes visible light getting converted to infrared, which can be detected by these devices only.

This was about infrared telescope and interesting facts associated with it. It has proved to be a vital invention in the research going on about detecting numerous celestial bodies. I hope you found this content helpful.