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Infrared telescope

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An infrared telescope is a specialized instrument designed to detect celestial bodies using infrared light. This light is a specific type of radiation found within the electromagnetic spectrum. Every object in the universe with a temperature above absolute zero emits some form of electromagnetic radiation. Scientists utilize many different types of telescopes to study these various emissions. These include tools for gamma rays, X-rays, ultraviolet light, and regular visible light, which is also called optical light. Infrared telescopes allow astronomers to observe the far, the cold, and the dusty parts of our universe.

IRAS overview
IRAS overview

To function, these telescopes use an infrared camera equipped with a solid-state infrared detector. This detector must be cooled to cryogenic temperatures to work properly. Cryogenic temperatures are extremely low temperatures required to maintain the sensitivity of the instrument. The mechanism relies on detecting radiation that would otherwise be lost to heat interference. By keeping the detector cold, the telescope can accurately capture the faint infrared signals from space. This process allows scientists to see objects that do not emit much visible light.

There are three main types of infrared telescopes based on where they are located. The first type is ground-based telescopes, which were the first used to observe the infrared universe. These became very popular during the mid-1960s. The second type is air-borne telescopes, which fly at high altitudes to get above much of the atmosphere. The third type is space-based telescopes, which operate entirely outside of Earth's atmosphere.

SOFIA with open telescope doors
SOFIA with open telescope doors

Placing telescopes in space is highly effective because it eliminates interference from the Earth's atmosphere.

Ground-based telescopes face a specific challenge because water vapor in the atmosphere absorbs infrared radiation. To combat this, scientists often place these telescopes on high mountains in very dry climates. This helps improve visibility by reducing the amount of water vapor in the way. In the 1960s, researchers experimented with using balloons to lift telescopes to higher altitudes. By 1967, scientists began placing infrared telescopes on rockets. These rockets served as the very first air-borne infrared telescopes in history.

The history of this technology involves many important scientific discoveries and inventions. In 1800, William Herschel discovered infrared radiation. Later, in 1878, Samuel Pierpoint Langley created the first bolometer. A bolometer is a sensitive instrument that can electrically detect tiny changes in temperature within the infrared spectrum. During the same year, Thomas Edison used a device called a tasimeter to measure heat in the Sun's corona. In the 1950s, scientists began using lead-sulfide detectors cooled with liquid nitrogen. Between 1959 and 1961, Harold Johnson developed near-infrared photometers to measure thousands of stars. Finally, Frank Low invented the germanium bolometer in 1961. This specific invention, which was cooled by liquid helium, paved the way for modern infrared telescope development.

Many significant projects have utilized these advancements to expand our knowledge. The Infrared Astronomical Satellite, or IRAS, launched in 1983 and provided vital information about other galaxies. It also revealed details about the center of our own Milky Way galaxy. In May 2010, NASA launched the Stratospheric Observatory for Infrared Astronomy, known as SOFIA. This was a massive 17-ton infrared telescope mounted on a Boeing 747 jet airplane. More recently, NASA launched the James Webb Space Telescope, or JWST, on December 25, 2021. The JWST is a solar-powered spacecraft that continues to study the cosmos.

Different telescopes are designed to look at different wavelengths of light. Typical infrared astronomy covers a range from 0.75 to 1000 micrometers. This range includes far-infrared and submillimetre astronomy. For example, the Spitzer Space Telescope operated between 3 and 180 micrometers. The Herschel Space Observatory looked at even longer wavelengths, from 55 to 672 micrometers. By using these different scales, scientists can build a complete picture of the physical world and the stars.

SOFIA with open telescope doors
SOFIA with open telescope doors
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File:SOFIA with open telescope doors.jpg
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File:IRAS overview.jpg
IRAS overview.jpg
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