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Definition: Mercury (astronomy) from The Macmillan Encyclopedia

The innermost and second smallest (4880 km diameter) planet, orbiting the sun every 88 days at a mean distance of 57.9 million km. Its long period of axial rotation, 58.6 days, is two-thirds of its orbital period. Mercury can only be seen low in the twilight and early morning sky and, like the moon, exhibits phases. Its surface is heavily cratered, with intervening lava-flooded plains. It has a very thin atmosphere, mainly helium and argon. See also planetary probe.

Mercury

From Britannica Concise Encyclopedia
Innermost planet of the solar system . Its average distance from the Sun is about 36 million mi (58 million km), but its highly elliptical orbit carries it 7.5 million mi (12 million km) nearer to and farther from the Sun. It is the smallest major planet, having a diameter of about 3,030 mi (4,880 km) and a mass about one-eighteenth of Earth’s. With the shortest period of revolution (only 88 Earth days) and the highest average orbital speed (30 mi/sec [48 km/sec]) of any planet, it is aptly named after the Roman fleet-footed messenger god. It spins very slowly, making one complete rotation relative to the stars every 59 Earth days, while its solar day (from one sunrise to the next) is 176 Earth days, owing to its revolution around the Sun. Its surface is heavily cratered. Its most impressive feature is perhaps the 960-mi (1,550-km) Caloris Basin, formed by a huge meteorite impact. Mercury also has steep cliffs that extend for hundreds of miles. The discovery of a magnetic field in its…
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Full text Article Mercury

From Astronomy Encyclopedia
Mercury Mariner 10 made three sets of...
Series of one-man spacecraft in which the USA first gained experience of space flight. The first flights, by modified Redstone boosters, were suborbital. On Mercury-Redstone 3, Alan SHEPARD became the first US astronaut to fly in space (1961 May 5). The capsule reached an altitude of 186km (116mi) …
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Full text Article Mercury

From Astronomy Encyclopedia
Innermost planet of the Solar System. Mercury is often described as the elusive planet, which is a misconception. Mercury is, in fact, easily picked up with the naked eye around the time of its greatest elongation from the Sun, when it can be followed without optical help for several days. …
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Full text Article Mercury

From Collins Dictionary of Astronomy
The innermost and, with a diameter of 4878 km, the second smallest planet in the Solar System, orbiting the Sun in 87.97 days at an average distance of 0.39 AU. It has no natural satellite. The distance from the Sun varies between 0.31 and 0.47 AU because of Mercury's high orbital eccentricity of…
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Full text Article mercury

From Merriam-Webster's Collegiate(R) Dictionary
pronunciation (14c) 1 a cap :  a Roman god of commerce, eloquence, travel, cunning, and theft who serves as messenger to the other gods compare hermes b often cap archaic :  a bearer of messages or news or a conductor of travelers 2 [ ME mercurie , fr. ML mercurius , fr. L, the god ] a :  a…
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Full text Article Mercury

From Philip's Encyclopedia
Smallest of the four inner planets, and the planet closest to the Sun. It has no known satellite. Very little was known about Mercury's surface until the Mariner 10 probe made three close approaches to the planet in 1974 and 1975, and returned pictures of nearly half the surface. These showed a…
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Description Time Total Time Mercury is the planet closest to the Sun. It consists of a large iron core covered with rocky materials. 00:01 – 00:11 00:00:55 We know very little about Mercury. A single space probe, Mariner 10, observed it in 1974. 00:12 – 00:22 Photographs taken by…
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Full text Article Mercury

From Britannica Concise Encyclopedia
Innermost planet of the solar system . Its average distance from the Sun is about 36 million mi (58 million km), but its highly elliptical orbit carries it 7.5 million mi (12 million km) nearer to and farther from the Sun. It is the smallest major planet, having a diameter of about 3,030 mi (4,880…
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The Planet Mercury and work in the field, detail from a miniature from De Sphaera by Leonardo Dati, Latin Manuscript folio 209 verso 10, 1470, Italy.
Credit: The Planet Mercury and work in the field, detail from a miniature from De Sphaera by Leonardo Dati, Latin Manuscript folio 209 verso 10, 1470, Italy. / De Agostini Picture Library / A. Dagli Orti / The Bridgeman Art Library Description: The Planet Mercury and work in the field, detail from a…
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Full text Article mercurial 1

From Merriam-Webster's Collegiate(R) Dictionary
pronunciation (14c) 1 :  of, relating to, or born under the planet Mercury 2 :  having qualities of eloquence, ingenuity , or thievishness attributed to the god Mercury or to the influence of the planet Mercury 3 :  characterized by rapid and unpredictable changeableness of mood 〈a ⁓ temper〉 4 : …
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Full text Article Mercury

From Brewer's Dictionary of Phrase and Fable
The Roman counterpart of the Greek hermes , son of maia and jupiter , to whom he acted as messenger. He was the god of science and commerce, the patron of travellers and also of rogues, vagabonds and thieves. Hence, the name of the god is used to denote both a messenger and a thief. Mercury is…
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