Astronomy Today

Airborne and Infrared Observatories

How does an infrared telescope work?

Infrared radiation can be divided roughly into near-infrared, mid-infrared or thermal-infrared, and far-infrared categories. Most ground-based telescopes on Earth can be used for observations of both visible light and near-infrared radiation; midinfrared light can be observed from Earth or from space; far-infrared radiation can only be observed effectively from space. Generally, infrared telescopes look and operate much like visible-light telescopes. However, since infrared radiation is a form of heat, telescopes and cameras used to observe infrared emissions from space work most effectively if they are cryogenically cooled—often using liquid helium, to temperatures less than ten degrees above absolute zero. The digital detectors are also made of different substances, to increase their sensitivity to infrared radiation. Whereas most visible light detectors are made primarily of silicon, near-infrared detectors are often made of germanium, or exotic materials like gallium arsenide, indium antimonide, or a blend of mercury, cadmium, and tellurium called “mer-cad-telluride.”


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