“gamma-ray astronomy”的概念、定义、翻译、参考文献-科学参考

gamma-ray astronomy

Physics

Astronomy involving gamma-ray photons (with energies in excess of 100 MeV). The cosmic radiation with the highest energy can be detected by electron–photon cascades, which take place in the atmosphere. Gamma rays having lower energies can only be detected above the atmosphere. Many high-energy processes in astrophysics are responsible for the production of gamma rays; one example is the decay of neutral pions.

An interesting phenomenon is the gamma-ray burst. These events last from several microseconds to several hundred seconds, during which they are the strongest source of gamma rays in the sky. Many theories have been put forward to explain gamma-ray bursts. It is thought that a gamma-ray burst occurs when a black hole is born, either when a very large star collapses or when two neutron stars collide. Gamma-ray bursts, and other aspects of gamma-ray astronomy, have been studied extensively since the late 20th century with various satellites.

Astronomy

The study of electromagnetic radiation from space at the very shortest wavelengths and with the highest photon energies (see gamma rays). Gamma rays are produced in regions of extremely high temperature, density, and magnetic fields, sites of the most violent processes in the Universe.
Many hundreds of individual gamma-ray sources are known, as well as a general gamma-ray background. Early experiments in the 1950s and 1960s used balloons to carry instruments to altitudes where the atmospheric absorption of gamma rays is low. Exploratory observations were also made with spacecraft, including Ranger and Apollo missions, during the 1960s. The first sky surveys were made by the satellites SAS-2 (see small astronomy satellite) and COS-B, launched in 1972 and 1974. In the late 1970s two High Energy Astrophysical Observatories (HEAO-1 and HEAO-3) carried gamma-ray experiments. The Granat satellite was launched in 1990, the Compton Gamma Ray Observatory in 1991, the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) in 2002, Swift in 2004, and the Fermi Gamma-ray Space Telescope in 2008.
The large energy range involved in gamma-ray astronomy necessitates several observational techniques. Only the very highest energies (above 100 GeV) can penetrate the Earth’s atmosphere, so most observations must be made from space. At the lowest energies (100 keV to 10 MeV) gamma-ray telescopes create images using the principle of the Compton effect, collimation, or the coded mask. Between 20 MeV and 30 GeV gamma-ray detection relies on the production of electron pairs using spark chambers and NaI detectors. Above 100 GeV the low photon fluxes require larger instruments than can be carried on satellites. For these energies, the Earth’s atmosphere is used as the detector, and optical telescopes record the Cerenkov radiation from the secondary particles produced by the primary gamma-ray photons.

Space Exploration

The study of celestial objects that emit gamma rays (energetic photons with very short wavelengths). Much of the radiation detected comes from collisions between hydrogen gas and cosmic rays in our Galaxy. Some sources have been identified, including the Crab Nebula and the Vela pulsar (the most powerful gamma-ray source detected).
Gamma rays are difficult to detect and are generally studied by use of balloon-borne detectors and artificial satellites. The first gamma-ray satellites were SAS II (1972) and COS-B (1975), although gamma-ray detectors were carried on the Apollo 15 and Apollo 16 missions, in 1971 and 1972, respectively. SAS II failed after only a few months, but COS-B continued working until 1982, carrying out a complete survey of the galactic disc.
The Compton Gamma-Ray Observatory was launched in April 1991 and the International Gamma-Ray Astrophysics Laboratory (Integral) in 2002. NASA’s Swift spacecraft was launched in 2004 and carries an instrument for gamma-ray burst detection. Italy’s small AGILE mission was launched in 2007, and NASA’s Fermi Gamma-ray Space Telescope was launched in 2008.

单词	gamma-ray astronomy
释义	gamma-ray astronomy Physics Astronomy involving gamma-ray photons (with energies in excess of 100 MeV). The cosmic radiation with the highest energy can be detected by electron–photon cascades, which take place in the atmosphere. Gamma rays having lower energies can only be detected above the atmosphere. Many high-energy processes in astrophysics are responsible for the production of gamma rays; one example is the decay of neutral pions. An interesting phenomenon is the gamma-ray burst. These events last from several microseconds to several hundred seconds, during which they are the strongest source of gamma rays in the sky. Many theories have been put forward to explain gamma-ray bursts. It is thought that a gamma-ray burst occurs when a black hole is born, either when a very large star collapses or when two neutron stars collide. Gamma-ray bursts, and other aspects of gamma-ray astronomy, have been studied extensively since the late 20th century with various satellites. Astronomy The study of electromagnetic radiation from space at the very shortest wavelengths and with the highest photon energies (see gamma rays). Gamma rays are produced in regions of extremely high temperature, density, and magnetic fields, sites of the most violent processes in the Universe. Many hundreds of individual gamma-ray sources are known, as well as a general gamma-ray background. Early experiments in the 1950s and 1960s used balloons to carry instruments to altitudes where the atmospheric absorption of gamma rays is low. Exploratory observations were also made with spacecraft, including Ranger and Apollo missions, during the 1960s. The first sky surveys were made by the satellites SAS-2 (see small astronomy satellite) and COS-B, launched in 1972 and 1974. In the late 1970s two High Energy Astrophysical Observatories (HEAO-1 and HEAO-3) carried gamma-ray experiments. The Granat satellite was launched in 1990, the Compton Gamma Ray Observatory in 1991, the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) in 2002, Swift in 2004, and the Fermi Gamma-ray Space Telescope in 2008. The large energy range involved in gamma-ray astronomy necessitates several observational techniques. Only the very highest energies (above 100 GeV) can penetrate the Earth’s atmosphere, so most observations must be made from space. At the lowest energies (100 keV to 10 MeV) gamma-ray telescopes create images using the principle of the Compton effect, collimation, or the coded mask. Between 20 MeV and 30 GeV gamma-ray detection relies on the production of electron pairs using spark chambers and NaI detectors. Above 100 GeV the low photon fluxes require larger instruments than can be carried on satellites. For these energies, the Earth’s atmosphere is used as the detector, and optical telescopes record the Cerenkov radiation from the secondary particles produced by the primary gamma-ray photons. Space Exploration The study of celestial objects that emit gamma rays (energetic photons with very short wavelengths). Much of the radiation detected comes from collisions between hydrogen gas and cosmic rays in our Galaxy. Some sources have been identified, including the Crab Nebula and the Vela pulsar (the most powerful gamma-ray source detected). Gamma rays are difficult to detect and are generally studied by use of balloon-borne detectors and artificial satellites. The first gamma-ray satellites were SAS II (1972) and COS-B (1975), although gamma-ray detectors were carried on the Apollo 15 and Apollo 16 missions, in 1971 and 1972, respectively. SAS II failed after only a few months, but COS-B continued working until 1982, carrying out a complete survey of the galactic disc. The Compton Gamma-Ray Observatory was launched in April 1991 and the International Gamma-Ray Astrophysics Laboratory (Integral) in 2002. NASA’s Swift spacecraft was launched in 2004 and carries an instrument for gamma-ray burst detection. Italy’s small AGILE mission was launched in 2007, and NASA’s Fermi Gamma-ray Space Telescope was launched in 2008.
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