- published: 08 Jul 2015
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The Hubble Space Telescope (HST) is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4-meter (7.9 ft) aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared. The telescope is named after the astronomer Edwin Hubble.
Hubble's orbit outside the distortion of Earth's atmosphere allows it to take extremely sharp images with almost no background light. Hubble's Ultra-Deep Field image, for instance, is the most detailed visible-light image ever made of the universe's most distant objects. Many Hubble observations have led to breakthroughs in astrophysics, such as accurately determining the rate of expansion of the universe.
Although not the first space telescope, Hubble is one of the largest and most versatile, and is well known as both a vital research tool and a public relations boon for astronomy. The HST was built by the United States space agency NASA, with contributions from the European Space Agency, and is operated by the Space Telescope Science Institute. The HST is one of NASA's Great Observatories, along with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space Telescope.
A space observatory is any instrument (such as a telescope) in outer space which is used for observation of distant planets, galaxies, and other outer space objects. This category is distinct from other observatories located in space that are pointed toward the earth for the purpose of reconnaissance and other types of information gathering.
A large number of observatories have been launched into orbit, and most of them have greatly enhanced our knowledge of the extraterrestrial universe.
Performing astronomy from the Earth's surface is limited by the filtering and distortion of electromagnetic radiation (scintillation or twinkling) due to the atmosphere. Some terrestrial telescopes (such as the Very Large Telescope) can reduce atmospheric effects with adaptive optics. A telescope orbiting the Earth outside the atmosphere is subject neither to twinkling nor to light pollution from artificial light sources on the Earth.
Space-based astronomy is even more important for frequency ranges which are outside of the optical window and the radio window, the only two wavelength ranges of the electromagnetic spectrum that are not severely attenuated by the atmosphere. For example, X-ray astronomy is nearly impossible when done from the Earth, and has reached its current importance in astronomy only due to orbiting X-ray telescopes such as the Chandra observatory and the XMM-Newton observatory. Infrared and ultraviolet are also greatly blocked.