“planet”的概念、定义、翻译、参考文献-科学参考

planet

Physics

A body that revolves around a central astronomical body. Traditionally, a planet was one of the nine bodies (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto) that revolve in elliptical orbit around the sun. In 2006, the International Astronomical Union (IAU) put forward a definition of a planet as a celestial body in orbit around the sun and having two additional properties. One is that it has sufficient mass to have hydrostatic equilibrium (i.e. essentially a spherical shape). The other is that the object should have cleared the neighbourhood of its orbit (i.e. is the main body in the orbit other than its own satellites). On this definition Pluto is not a planet because it has not cleared its orbit. Instead, it has been reclassified as a dwarf planet. Dwarf planets are objects that orbit the sun, have reached hydrostatic equilibrium, but have not cleared their orbits. Other objects in the solar system that have not reached hydrostatic equilibrium nor cleared their orbits are known as SSSBs (small solar system bodies). See also Solar System (Feature).

Astronomy

A non-luminous body in orbit around the Sun, or another star, which has sufficient mass to have become rounded by its own gravity and which has significantly cleared its orbital neighbourhood of smaller objects. Planets can consist of rock and metal, as do the inner planets of the Solar System, or predominantly of liquid and gas, as do the giant outer planets. The term does not include comets or other small objects such as meteoroids. Asteroids, however, are sometimes referred to as minor planets. A planet can have a mass up to about 10 times that of Jupiter, above which it would become a brown dwarf. In 2006 the International Astronomical Union introduced the term dwarf planet to describe objects that are rounded in shape but which have not cleared the neighbourhood around their orbit; this category includes the largest member of the asteroid belt, Ceres, and the largest trans-Neptunian objects.

Space Exploration

A large celestial body in orbit around a star, composed of rock, metal, or gas. There are nine planets in the Solar System orbiting the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Neptune, Uranus, and Pluto. The inner four, called the terrestrial planets, are small and rocky, and have few natural satellites. The outer planets, with the exception of Pluto, are called the major planets, and have denser atmospheres consisting mainly of hydrogen and helium gases, and many natural satellites. The largest planet in the Solar System is Jupiter (about 780 million km from the Sun) with a diameter of 140 000 km, which contains a mass greater than all the other planets combined. The smallest (and furthest from the Sun at about 5 900 million km) is Pluto with a diameter of 2 300 km.
Planets of other stars are now being discovered, and are known as extrasolar planets.
Space probes to planets include Mariner 2 (launched in 1962 to Venus), Pioneer 10 (launched in 1972 to Jupiter), Mariner 10 (launched in 1973 to Venus and Mercury), Viking 1 and Viking 2 (launched in 1975 to Mars), Voyager 1 and Voyager 2 (launched in 1977) to Jupiter and Saturn, Galileo (launched in 1989 to Jupiter), and Cassini (launched in 1997 to Saturn), and numerous missions to Mars in the 1990s.
http://nssdc.gsfc.nasa.gov/planetary/ NASA archive of planetary data and images. The site includes fact sheets and press releases, information on forthcoming missions, and a useful chronology of lunar and planetary exploration. There is also information about the impact of the comet Shoemaker–Levy 9 with Jupiter.

单词	planet
释义	planet Physics A body that revolves around a central astronomical body. Traditionally, a planet was one of the nine bodies (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto) that revolve in elliptical orbit around the sun. In 2006, the International Astronomical Union (IAU) put forward a definition of a planet as a celestial body in orbit around the sun and having two additional properties. One is that it has sufficient mass to have hydrostatic equilibrium (i.e. essentially a spherical shape). The other is that the object should have cleared the neighbourhood of its orbit (i.e. is the main body in the orbit other than its own satellites). On this definition Pluto is not a planet because it has not cleared its orbit. Instead, it has been reclassified as a dwarf planet. Dwarf planets are objects that orbit the sun, have reached hydrostatic equilibrium, but have not cleared their orbits. Other objects in the solar system that have not reached hydrostatic equilibrium nor cleared their orbits are known as SSSBs (small solar system bodies). See also Solar System (Feature). Astronomy A non-luminous body in orbit around the Sun, or another star, which has sufficient mass to have become rounded by its own gravity and which has significantly cleared its orbital neighbourhood of smaller objects. Planets can consist of rock and metal, as do the inner planets of the Solar System, or predominantly of liquid and gas, as do the giant outer planets. The term does not include comets or other small objects such as meteoroids. Asteroids, however, are sometimes referred to as minor planets. A planet can have a mass up to about 10 times that of Jupiter, above which it would become a brown dwarf. In 2006 the International Astronomical Union introduced the term dwarf planet to describe objects that are rounded in shape but which have not cleared the neighbourhood around their orbit; this category includes the largest member of the asteroid belt, Ceres, and the largest trans-Neptunian objects. Space Exploration A large celestial body in orbit around a star, composed of rock, metal, or gas. There are nine planets in the Solar System orbiting the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Neptune, Uranus, and Pluto. The inner four, called the terrestrial planets, are small and rocky, and have few natural satellites. The outer planets, with the exception of Pluto, are called the major planets, and have denser atmospheres consisting mainly of hydrogen and helium gases, and many natural satellites. The largest planet in the Solar System is Jupiter (about 780 million km from the Sun) with a diameter of 140 000 km, which contains a mass greater than all the other planets combined. The smallest (and furthest from the Sun at about 5 900 million km) is Pluto with a diameter of 2 300 km. Planets of other stars are now being discovered, and are known as extrasolar planets. Space probes to planets include Mariner 2 (launched in 1962 to Venus), Pioneer 10 (launched in 1972 to Jupiter), Mariner 10 (launched in 1973 to Venus and Mercury), Viking 1 and Viking 2 (launched in 1975 to Mars), Voyager 1 and Voyager 2 (launched in 1977) to Jupiter and Saturn, Galileo (launched in 1989 to Jupiter), and Cassini (launched in 1997 to Saturn), and numerous missions to Mars in the 1990s. http://nssdc.gsfc.nasa.gov/planetary/ NASA archive of planetary data and images. The site includes fact sheets and press releases, information on forthcoming missions, and a useful chronology of lunar and planetary exploration. There is also information about the impact of the comet Shoemaker–Levy 9 with Jupiter.
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