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Definition: Neptune (astronomy) from The Macmillan Encyclopedia

The most distant giant planet, orbiting the sun every 165 years at a mean distance of 4497 million km. It is somewhat smaller (48 600 km in diameter) and more massive (17.2 earth masses) than Uranus, exhibits a similar featureless greenish disc in a telescope, and is thought to be almost identical to Uranus in atmospheric and internal structure. It has eight satellites. Neptune's existence was predicted by John Couch Adams and Urbain Leverrier. It was discovered in 1846 by J. G. Galle, using Leverrier's predicted position. In 1989 it was circumnavigated by Voyager 2.


Neptune

From Encyclopedia of the History of Astronomy and Astrophysics
Alexis Bouvard tried to calculate an orbit for Uranus in 1820 using both pre-discovery and post-discovery observations. But he could not find a single orbit to fit them. The best that he could produce was an orbit based on only the post-discovery observations, but this implied that some of the pre-discovery observations were in error by up to 65″, which seemed very unlikely. Unfortunately, it did not take long for Uranus to deviate increasingly from even this orbit, so that by 1845 the longitude discrepancy had reached about 2′. One possible explanation was that Uranus was being disturbed by another planet, and in 1836 Friedrich Nicolai suggested, that if the Titius-Bode series was correct, the unknown planet would be about 38 AU from the Sun. John Couch Adams, an English mathematician, set out in 1843 to try to calculate the orbit of the planet that seemed to be disturbing the orbit of Uranus. By September 1845, he had calculated its orbital elements and its expected position in the…
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Full text Article Neptune

From Astronomy Encyclopedia
Neptune Neptune appears bluish because methane in...
Eighth planet from the Sun. It is the fourth largest (by diameter) and the third most massive planet. From 1979 to 1999 PLUTO , thanks to its eccentric orbit, was nearer to the Sun than Neptune: during this period Neptune was thus the ninth and farthest known planet. At magnitude +7.8, Neptune is…
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Full text Article Neptune

From Philip's Encyclopedia
Eighth planet from the Sun. The mass, orbit, and position of an unseen planet had been calculated by Leverrier and, independently, by British astronomer John Couch Adams (1819-92). Neptune was first observed in 1846, and is invisible to the naked eye. Through a telescope it appears as a small, …
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Full text Article Neptune

From The New Dictionary of Cultural Literacy, Houghton Mifflin
In astronomy , a major planet , the eighth planet from the sun . Neptune is named for the Roman god of the sea. Neptune is similar in size and composition to Uranus . It is usually visible only through a telescope and was discovered in the 1840s. For a period ending in 1999, Pluto' …
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Full text Article Neptune

From Encyclopedia of the History of Astronomy and Astrophysics Full text Article The solar system Full text Article Giant planets
This image of Triton, which is about...
Alexis Bouvard tried to calculate an orbit for Uranus in 1820 using both pre-discovery and post-discovery observations. But he could not find a single orbit to fit them. The best that he could produce was an orbit based on only the post-discovery observations, but this implied that some of the…
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Full text Article Neptune

From Collins Dictionary of Astronomy
The eighth planet of the Solar System, orbiting the Sun every 164.79 years at an almost constant distance of 30.06 AU. It is the most distant giant planet. It has a diameter of 50 538 km, a mass of 17.2 Earth-masses, and a density of 1.76 times that of water. Neptune has 13 known satellites; Triton…
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Full text Article Neptune

From Science Encyclopedia: Encyclopedia of Space and Astronomy
Neptune is the farthest primary planet from the...
The outermost of the Jovian planets and the first planet to be discovered using theoretical predictions. Neptune's discovery was made by the German astronomer Johann Gottried Galle at the Berlin Observatory in 1846. This discovery was based on independent orbital perturbation (disturbance) analyses…
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Full text Article Neptune

From Britannica Concise Encyclopedia
Eighth planet from the Sun, discovered in 1846 and named for the Roman god of the sea. It has an average distance from the Sun of 2.8 billion mi (4.5 billion km), taking nearly 164 years to complete one orbit and rotating every 16.11 hours. Neptune has more than 17 times Earth’s mass, 58 times its…
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From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
Eighth planet in average distance from the Sun. It is a giant gas (hydrogen, helium, methane) planet, with a mass 17.2 times that of Earth. It has the fastest winds in the Solar System. Mean distance from the Sun 4.4 billion km/2.794 billion mi Equatorial diameter 48,600 km/30,200 mi Rotation period…
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Description Time Total Time Located more than 4.5 billion kilometers from the Sun, Neptune is one of the gas giants of the solar system. 00:01 – 00:11 00:01:10 Composed of rock, ice, and hydrogen, it has a thick envelope of gases, mainly hydrogen and helium. Traces of methane give Neptune its…
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From The Classical Tradition
Neptune was the Roman god of fresh and salt water, a conflation of the Etruscan god of wells (Nethuns) and the Greek god of the sea (Poseidon). Though in antiquity Neptune was often pictured similarly to his brother Jupiter, as a vigorous man with copious locks and a wavy beard, images of him…
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