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orbit
orbit in astronomy, path in space described by a body revolving about a second body where the motion of the orbiting bodies is dominated by their mutual gravitational attraction. Within the solar system, planets, dwarf planets, asteroids, and comets orbit the sun and satellites orbit the planets an...
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artificial satellite
artificial satellite object constructed by humans and placed in orbit around the earth or other celestial body (see also space probe ). The satellite is lifted from the earth's surface by a rocket and, once placed in orbit, maintains its motion without further rocket propulsion. The first artifi...
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molecular orbital theory
molecular orbital theory detailed explanation of how electrons are distributed in stable molecules . In the simpler valence theory of the chemical bond , each atom in a molecule is assumed to retain its own electrons. Even when electrons are shared, as in the covalent bond, it is possible to id...
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Pluto
Pluto in astronomy, a dwarf planet and the first Kuiper belt, or transneptunian, object (see comet ) to be discovered (1930) by astronomers. Pluto has an elliptical orbit usually lying beyond that of Neptune . Although Pluto was long regarded as a planet, since the discovery (beginning in 1992) o...
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inclination
inclination in astronomy, the angle of intersection between two planes, one of which is an orbital plane. The inclination of the plane of the moon's orbit is 5°9′ with respect to the plane of the ecliptic (the plane of the earth's orbit around the sun). The inclination of the plane of the...
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apsis
apsis (pl. apsides), point in the orbit of a body where the body is neither approaching nor receding from another body about which it revolves. Any elliptical orbit has two apsides. At the perigee the moon or other satellite is as close as it ever gets to the earth, and it begins to move away; at...
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Helene
Helene , in astronomy, one of the named moons, or natural satellites, of Saturn . Also known as Saturn XII (or S12), Helene is an irregularly shaped (nonspherical) body measuring about 22 mi (36 km) by 20 mi (32 km) by 18 mi (30 km); it orbits Saturn at a mean distance of 234,500 mi (377,400 km) an...
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Telesto
Telesto , in astronomy, one of the named moons, or natural satellites, of Saturn . Also known as Saturn XIII (or S13), Telesto is an irregularly shaped (nonspherical) body measuring about 21 mi (34 km) by 17 mi (28 km) by 16 mi (26 km); it orbits Saturn at a mean distance of 183,093 mi (294,660 km)...
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space shuttle
space shuttle Re-usable rocket-powered US spacecraft. The main part of the shuttle, the orbiter (of which four have been built, Columbia, Challenger, Discovery, and Atlantis), looks like a bulky jet aircraft with swept-back wings. It ferries people and equipment between the ground and Earth orbit. ...
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Epimetheus
Epimetheus in astronomy, one of the named moons, or natural satellites, of Saturn . Also known as Saturn XI (or S11), Epimetheus is an irregularly shaped (nonspherical) body measuring about 89 mi (144 km) by 67 mi (108 km) by 61 mi (98 km); it orbits Saturn at a mean distance of 94,090 mi (151,422...
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