Space Telescope - astronomy.

Space Telescope - astronomy. I INTRODUCTION Space Telescope, telescope or other astronomical detector mounted on an artificial satellite, a manned spacecraft, or another device outside Earth's atmosphere. The best-known and most famous space telescope is the Hubble Space Telescope (HST), in Earth orbit since 1990. Dozens of other space telescopes have been launched since the 1960s to study galaxies, stars, planets, and other objects and phenomena in space. Observations made by telescopes in space have helped revolutionize our view of the universe, making major contributions to astronomy, physics and astrophysics, planetary sciences, and cosmology. With advancing technologies, the capabilities of new space telescopes continue to improve. At the same time new ground-based telescopes also become more sensitive and more powerful, sometimes equaling or exceeding results from earlier space telescopes. Space telescopes have several advantages over Earth-based telescopes. Telescopes in space offer a much clearer view of astronomical objects because their instruments are far above Earth's turbulent, distorting atmosphere. Telescopes in space are free from light pollution, artificially generated light that makes it difficult to observe faint astronomical objects. Space telescopes also can cover the entire celestial sphere, whereas portions of the sky may not be accessible to stationary groundbased telescopes, depending on their location on Earth. Space telescopes also are not limited to observing the narrow band of light that is visible to the eye. Instead they have access to the entire electromagnetic spectrum, including infrared light, ultraviolet light, X rays, and gamma rays. The atmosphere entirely blocks some portions of the spectrum from reaching the ground, so satellites that can detect radiation from those portions offer new windows onto the universe that carry a wealth of information about planets, stars, and galaxies, and also the processes that shape them. Phenomena such as active galaxies and black holes cannot be fully understood without comparing data from across the electromagnetic spectrum. Space telescopes range in complexity from small satellites, which often survey the entire sky, to larger "observatory-class" satellites, which can target particular objects. These larger satellites generally require more intensive control from scientists on the ground, who choose objects to be studied and help point the satellites in the correct direction. II EARLY SPACE TELESCOPES Nearly a century ago Russian theorist Konstantin Tsiolkovsky and German rocket scientist Hermann Oberth recognized the advantage of placing an astronomical telescope in space, where starlight would not be blurred by the turbulence of Earth's atmosphere. But it was not until after World War II (1939-1945), when rocket boosters were developed capable of hurtling satellites into orbit, that the dream of space-based astronomy became reality. The British Ariel program launched the first astronomical satellites. Ariel 1, launched in April 1962, studied the Sun's ultraviolet and X-ray emissions. The next space telescopes were from the Orbiting Astronomical Observatory (OAO) program of the United States National Aeronautics and Space Administration (NASA). OAO 2, the first successful OAO, was launched in December 1968 and carried infrared, ultraviolet, X-ray, and gamma-ray detectors and telescopes. As the first of their kind, these satellites provided valuable background for later and more complex space telescopes. III TYPES OF SPACE TELESCOPES The Hubble Space Telescope is a general-purpose observatory that can detect different types of electromagnetic radiation from infrared to ultraviolet. However, most space telescopes are designed to study a particular range of wavelengths on the electromagnetic spectrum. The major divisions of the spectrum from longest to shortest wavelength are: radio, microwave, infrared, visible light, ultraviolet radiation, X ray, and gamma ray. Radio waves easily penetrate Earth's atmosphere, so radio telescopes can be ground-based. A Microwave Space Telescopes Space telescopes that detect microwaves are used to study the earliest stages of the universe after the big bang 13.7 billion years ago. See also Background Radiation; Big Bang Theory. B Infrared Space Telescopes Earth's atmosphere emits infrared radiation, called infrared background glow, which interferes with readings by ground-based infrared telescopes. The atmosphere also contains water vapor that absorbs some infrared radiation, preventing it from reaching ground-based infrared telescopes. Infrared telescopes in space are not hampered by background glow and are extraordinarily sensitive to faint infrared sources. See also Infrared Astronomy; Infrared Space Observatory; Spitzer Space Telescope; James Webb Space Telescope. C Visible-Light Space Telescopes Visible-light observations from space have the advantage of a clearer image. Ground-based telescopes are hampered by interference by Earth's atmosphere, which produces fuzzy images. Space telescopes designed to detect visible light have been used to study galaxies, stars, planets, and objects in the solar system. See also Hubble Space Telescope. D Ultraviolet Space Telescopes Some of the hottest and most energetic stars in the universe are visible in the ultraviolet region of the electromagnetic spectrum. Sources include the atmospheres of young stars, the surfaces of hot white dwarf stars and the cores of active galaxies. See also Ultraviolet Astronomy. D1 X-Ray Space Observatories Earth's atmosphere absorbs almost all the X rays that enter it from space. X rays are often associated with high-energy events that are of interest to astronomers. Supernovas (stars that explode at the end of their lives) and the centers of active galaxies emit X rays. X rays are also emitted by binary star systems in which the gravitational pull of a small, dense star such as a white dwarf (a very compact, small star) or a neutron star (the collapsed remnant of a massive star) is pulling gas off of its normal companion star and heating it to millions of degrees. See also X-Ray Astronomy; Chandra X-Ray Observatory. D2 Gamma-Ray Space Observatories Studying gamma rays offers scientists answers to some of the most perplexing questions about the explosive and dynamic physical processes in the universe. Gammaray observation also provides clues about the structure and dynamics of the Milky Way and other galaxies; the nature of pulsars, quasars, black holes, and neutron stars; and the origin and history of the universe itself. See also Gamma-Ray Astronomy; Compton Gamma Ray Observatory. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.