Neptune, in Roman religion and mythology
Neptune, in Roman religion and mythology, god of water. He was presumably an indigenous god of fertility, but in later times he was identified with the Greek Poseidon Poseidon , in Greek religion and mythology, god of the sea, protector of all waters. After the fall of the Titans, Poseidon was allotted the sea. He was worshiped especially in connection with navigation; but as the god of fresh waters he also was worshiped as a..... Click the link for more information. , god of the sea. At his festival, the Neptunalia (July 23), arbors were dedicated to him.
Neptune, in astronomy
Neptune, in astronomy, 8th planet from the sun at a mean distance of about 2.8 billion mi (4.5 billion km) with an orbit lying between those of Uranus and the dwarf planet Pluto; its period of revolution is about 165 years. (Pluto has such a highly elliptical orbit that from 1979 to 1999 it was closer to the sun than Neptune; it will remain farther from the sun for 220 years, when it will again pass inside Neptune's orbit.) Neptune was discovered as the result of observed irregularities in the motion of Uranus and was the first planet to be discovered on the basis of theoretical calculations. J. C. Adams of Britain and U. J. Leverrier of France independently predicted the position of Neptune, and it was discovered by J. C. Galle in 1846, the day after he received Leverrier's prediction. Neptune has an equatorial diameter of about 30,700 mi (49,400 km), nearly four times that of the earth, and a mass about 17 times the earth's mass. It is much like Uranus and the other giant planets, with a thick atmosphere of hydrogen, helium, methane, and ammonia, a relatively low density, and a rapid period of rotation. On Aug. 24–25, 1989, the U.S. spacecraft Voyager 2 observed Neptune and its moons. It discovered that Neptune's atmosphere has zones like Jupiter's as well as giant storm systems as dark spots on its surface. Although Neptune receives a much smaller fraction of the sun's radiation than does Uranus, its surface temperature is similar: −350°F; (−212°C;).This may indicate a possible internal heat source. Neptune's largest moon, Triton, was discovered in 1846, a month after the discovery of the planet itself. Triton has a diameter of about 1,700 mi (2,700 km), and its motion is retrograde (see retrograde motion retrograde motion, in astronomy, real or apparent movement of a planet, dwarf planet, moon, asteroid, or comet from east to west relative to the fixed stars...... Click the link for more information. ), i.e., opposite to that of the planet's rotation. Its surface temperature is −400°F; (−240°C;), making it one of the coldest objects in the solar system. Nereid, discovered in 1949, has a diameter of about 210 mi (338 km), is very faint, and has a highly elliptic orbit; it may be of asteroid origin. Voyager discovered six smaller dark moons orbiting between the planet and Triton: Naiad, Thalassa, Despina, Galatea, Larissa, and Proteus—all irregularly shaped, ranging from 35 to 260 mi (58–418 km) in diameter. Since Neptune was named for the Roman god of the sea, its moons were named for various lesser sea gods and nymphs in Greek mythology. Five additional moons, as yet unnamed, were discovered using earth-based telescopes in 2002 and 2003. Voyager also found a faint ring ring, in astronomy, relatively thin band of rocks and dust and ice particles that orbit around a planet in the planet's equatorial plane. All four of the giant planets in the solar system—Jupiter, Saturn, Uranus, and Neptune— have rings, although only
..... Click the link for more information. system with three bands. These are named Adams, Leverrier, and Galle in honor of the planet's discoverers. Composed of small rocks and dust, the rings are not uniform in thickness or density. Adams, the outermost, contains three prominent arcs named Liberty, Equality, and Fraternity.
Bibliography
See P. Moore, Planet Neptune (1989); E. Burgess, Far Encounter: The Neptune System (1992); G. E. Hunt et al., Atlas of Neptune (1994).
Neptune
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 volume, and 12% stronger gravity at the top of its atmosphere. It has an equatorial diameter of 30,775 mi (49,528 km). Neptune consists largely of hydrogen and helium. It has no solid surface; its interior is believed to consist of a fluid mixture of rock, ices, and gas. Its atmosphere contains substantial amounts of methane gas, whose absorption of red light causes Neptune's deep blue-green colour. The Voyager 2 space probe in 1989 discovered winds of over 1,570 mi/hour (700 m/second), the fastest known for any of the Sun's planets, and dark spots that appear to be storms similar to Jupiter's Great Red Spot. Neptune receives little solar radiation, but it radiates substantially more energy than it receives, which indicates an internal heat source. Neptune's weak magnetic field traps charged particles in a belt around the planet. Neptune has a system of rings, made up largely of dust-size particles, and at least 13 moons; the largest is Triton, almost as big as Earth's Moon.
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Neptune [′nep·tün]
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Neptune
a principal planet of our solar system, the eighth in distance from the sun. It has the astronomical sign ψ. Neptune was discovered in 1846. Its mean distance from the sun (semimajor axis of the orbit) is 30.06 astronomical units, or 4.5 billion km. The eccentricity of Neptune’s orbit is 0.0086, and the inclination to the plane of the ecliptic is 1° 46.4’. Neptune makes a complete revolution around the sun (sidereal period of revolution) in 164.79 years with an average orbital velocity of 5.4 km/sec. In the sky, the planet (which cannot be seen by the unaided eye) looks like a star of 7.8 magnitude with an angular diameter varying from 2.2“ to 2.4”. With powerful magnification, it appears as a greenish disk without any details. Neptune’s diameter is 49,500 km, which is 3.88 times the equatorial diameter of the earth. The oblateness of the planet is estimated to be 1/60. Neptune’s volume is 57 times greater than the earth’s volume. Its mass is 17.28 times that of the earth (1.03 × 1026 kg), and its mean density is 1.84 g/cm3. The acceleration of the force of gravity on the surface of Neptune is about 11 m/sec2 (15 percent more than on the earth). The second critical spacecraft velocity (escape velocity) at the surface of Neptune is 23 km/sec. Neptune’s period of rotation about its axis is 15.8 hr. Neptune’s equator is inclined at an angle of 29° to the plane of its orbit.
The planet has two satellites. Triton, discovered by W. Lassell in 1846, is comparatively large, with a diameter of about 4,000 km, and revolves around Neptune in the retrograde direction with a period of about 5.9 days. The second satellite, Nereid, was discovered in 1949 by the American astronomer G. P. Kuiper. A small body, with a diameter of 300 km, it revolves around the planet with a period of about one year (360 days).
Neptune receives very little light and heat because of its remoteness from the sun and because the atmosphere of Neptune scatters into space up to 83 percent of the incident radiation. Strong absorption bands of methane (CH4) are observed in the spectrum of Neptune; these bands are particularly intense at the red end of the spectrum, which causes the planet to have a greenish color. Neptune’s equilibrium temperature is —220°C. Radio measurements yield a temperature of about —160°; this latter temperature evidently refers to a layer under the clouds and indicates that the planet does have its own heat. Traces of molecular hydrogen H2 have also been detected in the spectrum of Neptune; however, the predominant element in the atmosphere and interior of Neptune is probably helium; evidence for this is the comparatively high mean density of the planet.
The discovery of Neptune was one of the most remarkable achievements of astronomy. In 1783, just two years after the discovery of the planet Uranus, A. J. Lexell, who had studied the motion of Uranus and was the first to compute its orbital elements, expressed the hypothesis that the irregularities detected in the motion of Uranus were caused by the gravitational attraction of an unknown planet revolving about the sun beyond the orbit of Uranus. J. C. Adams and U. Leverrier, completely unknown to one another, proceeded in a similar way in the search for this planet in the mid-19th century. In September 1845, Adams reported the results of his computations, which contained all the orbital elements and the position of the planet in the sky, to G. Airy, director (astronomer royal) of the Royal Greenwich Observatory. Airy did not familiarize himself with Adams’ work until nine months after he had received it. Meanwhile, Leverrier had computed the orbital elements of the new planet and its position in the sky and reported his results to the Berlin Astronomical Observatory on Sept. 18, 1846. The planet was discovered by J. Galle on Sept. 23, 1846, the first evening after the letter was received. The planet was found just 52’ from the computed position.
D. IA. MARTYNOV
Neptune
in ancient Roman mythology, the god of springs and rivers. Later identified with the ancient Greek god Poseidon, Neptune was worshiped as the god of the seas, who agitated and calmed them with his trident. In Rome, a temple to Neptune was erected in the Circus Flaminius; a holiday honoring him (Neptunalia) was celebrated on July 23.
In a figurative sense Neptune means the element of the sea.
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