Einstein Observatory

satellite

Also known as: HEAO-2, High Energy Astronomy Observatory-2

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June 26, 2026

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The Einstein Observatory was an X-ray telescope launched into orbit to study celestial objects from outside Earth's atmosphere. Because X-rays are absorbed by the atmosphere, X-ray telescopes must be placed in orbit or carried by rockets or balloons. The Einstein Observatory was one of the High-Energy Astronomy Observatories (HEAO) and was used to study cosmic X-ray sources in detail. Unlike conventional optical telescopes, X-ray telescopes use a technique called grazing incidence, where X-rays bounce off mirrors at a very low angle to be focused and form an image. Other X-ray observatories include the European X-ray Observatory Satellite (EXOSAT), the Röntgensatellit (ROSAT), and the Chandra X-ray Observatory.1

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Riccardo Giacconi
Called the Einstein Observatory (launched 1978), it examined stellar atmospheres and supernova remnants, identified many X-ray double stars (some containing suspected black holes), and detected X-ray sources in other galaxies. In 1976 Giacconi proposed a still more powerful instrument, which was finally launched in 1999 as the…
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Called the Einstein Observatory (launched 1978), it examined stellar atmospheres and supernova remnants, identified many X-ray double stars (some containing suspected black holes), and detected X-ray sources in other galaxies. In 1976 Giacconi proposed a still more powerful instrument, which was finally launched in 1999 as the…
Read More

intergalactic medium
…imaging X-ray telescope aboard the Einstein Observatory (the HEAO 2 satellite), however, showed that a large fraction of the seemingly diffuse background of hard X rays, perhaps all of it, could be accounted for by a superposition of previously unresolved point sources—i.e., quasars. Subsequent research demonstrated that the shape of…
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…imaging X-ray telescope aboard the Einstein Observatory (the HEAO 2 satellite), however, showed that a large fraction of the seemingly diffuse background of hard X rays, perhaps all of it, could be accounted for by a superposition of previously unresolved point sources—i.e., quasars. Subsequent research demonstrated that the shape of…
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X-ray source
…2 satellite known as the Einstein Observatory. It detected more than 150 ordinary stars by the X-radiation from their coronas. The stars observed cover almost the entire range of star-types—main sequence, red giants, and white dwarfs. Most stars emit only an extremely small fraction of their energy in the form…
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…2 satellite known as the Einstein Observatory. It detected more than 150 ordinary stars by the X-radiation from their coronas. The stars observed cover almost the entire range of star-types—main sequence, red giants, and white dwarfs. Most stars emit only an extremely small fraction of their energy in the form…
Read More