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perihelion
(Encyclopedia)perihelion pĕrˌəhēˈlēən [key], point nearest the sun in the orbit of a body about the sun. See apsis. ...apsis
(Encyclopedia)CE5 Apsis points, or apsides, in the earth's orbit: At perihelion the earth is closest to the sun and at aphelion it is farthest from the sun. apsis (pl. apsides), point in the orbit of a body whe...Vulcan, in astronomy
(Encyclopedia)Vulcan, in astronomy, hypothetical planet whose existence was proposed by Le Verrier to explain part of the advance of the perihelion of Mercury, not all of which could be accounted for by gravitation...anomalistic year
(Encyclopedia)anomalistic year ənŏmˌəlĭsˈtĭk [key], time required for the earth to go from the perihelion point once around the sun and back to the perihelion point. It is 365 days, 6 hr, 13 min, 53.0 sec of...perturbation
(Encyclopedia)perturbation pŭrˌtərbāˈshən [key], in astronomy and physics, small force or other influence that modifies the otherwise simple motion of some object. The term is also used for the effect produce...Vesta, in astronomy
(Encyclopedia)Vesta vĕsˈtə [key], in astronomy, the fourth asteroid to be discovered. It was found in 1807 by H. Olbers. It is the third largest asteroid in size, with a diameter of c.326 mi (525 km). Its averag...Mercury, in astronomy
(Encyclopedia)Mercury, in astronomy, nearest planet to the sun, at a mean distance of 36 million mi (58 million km); its period of revolution is 88 days. Mercury passes through phases similar to those of the moon a...Mars, in astronomy
(Encyclopedia)Mars, in astronomy, 4th planet from the sun, with an orbit next in order beyond that of the earth. Mars has two natural satellites, discovered by Asaph Hall in 1877. The innermost of these, Phobos...orbit
(Encyclopedia)CE5 Important points in a planet's orbit as seen from the earth orbit, in astronomy, path in space described by a body revolving about a second body where the motion of the orbiting bodies is domi...sun, in astronomy
(Encyclopedia)CE5 Structure of the sun sun, intensely hot, self-luminous body of gases at the center of the solar system. Its gravitational attraction maintains the planets, comets, and other bodies of the sola...Browse by Subject
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