Neptune Essay, Research Paper

Neptune

Neptune is the outermost planet of the gas giants. It has an equatorial

diameter of 49,500 kilometers (30,760 miles) and is the eighth planet from the

sun. If Neptune were hollow, it could contain nearly 60 Earth’s. Neptune

orbits the Sun every 165 years. It has eight moons, six of which were found by

Voyager 2. A day on Neptune is 16 hours and 6.7 minutes. Neptune was

discovered on September 23, 1846 by Johann Gottfried Galle, of the Berlin

Observatory. Neptune got its named from the Roman God of the Sea. Much of what

is know today about Neptune was discovered in 1989 by the U.S Voyager 2

spacecraft during its 1989 flyby f Neptune. Neptune as compared to Earth is 3.9

times the diameter, 30 times the distance from the sun, 17 times as massive, and

0.3 times the density. Neptune travels around the Sun in an elliptical orbit at

an average distance of 4.504 billion km (2.799 billion miles). Neptune consists

largely of hydrogen and helium, and it has no apparent solid surface. The first

two thirds of Neptune is composed of a mixture of molten rock, water, liquid

ammonia and methane. The outer third is a mixture of heated gases comprised of

hydrogen, helium, water and methane. The atmospheric composition is 85%

Hydrogen, 13% Helium, and 2% methane. The planet’s atmosphere, particularly

the outer layers, contains substantial amounts of methane gas. Absorption of

red light by the atmospheric methane is responsible for Neptune’s deep blue

color. Neptune is a dynamic planet with several large, dark spots reminiscent of

Jupiter’s hurricane-like storms. The largest spot, known as the Great Dark Spot,

is about the size of the earth and is similar to the Great Red Spot on Jupiter.

Neptune receives less than half as much sunlight as Uranus, but heat escaping

from its interior makes Neptune slightly warmer than Uranus. The heat liberated

may also be responsible for Neptune’s stormier atmosphere, which exhibits the

fastest winds seen on any planet in the solar system. Most of the winds there

blow westward, opposite to the rotation of the planet. Near the Great Dark Spot,

winds blow up to 2,000 kilometers (1,200 miles) an hour. Voyager 2 found that

the winds averaged about 300 meters per second (700 miles/hour) in the planet’s

atmosphere.

Long bright clouds, similar to cirrus clouds on Earth, were seen high in

Neptune’s atmosphere. At low northern latitudes, Voyager captured images of

cloud streaks casting their shadows on cloud decks below.

Feathery white clouds fill the boundary between the dark and light blue regions

on the Great Dark Spot. The pinwheel shape of both the dark boundary and the

white cirrus suggests that the storm system rotates counterclockwise. Periodic

small scale patterns in the white cloud, possibly waves, are short lived and do

not persist from one Neptunian rotation to the next. (Courtesy NASA/JPL)

Until the Voyager 2 encounter in 1989, the rings surrounding Neptune were

thought to be arcs. We now know that the rings completely circle the planet, but

the thickness of each ring varies along its length. Neptune has a set of four

rings which are narrow and very faint. The rings are made up of dust particles

thought to have been made by tiny meteorites smashing into Neptune’s moons.

From ground based telescopes the rings appear to be arcs but from Voyager 2 the

arcs turned out to be bright spots or clumps in the ring system. The exact

cause of the bright clumps is unknown. The magnetic field of Neptune, like that

of Uranus, is highly tilted at 47 degrees from the rotation axis and offset at

least 13,500 kilometers or 8,500 miles from the physical center. Comparing the

magnetic fields of the two planets, scientists think the extreme orientation may

be characteristic of flows in the interior of the planet and not the result of

that planet’s sideways orientation or of any possible field reversals within the

planet. Neptune also has eight known satellites. Only two of these, Triton and

Nereid, had been observed prior to the Voyager 2 flyby. Triton is the largest

of the eight satellites and is almost as big as the Earth’s Moon. The other

Neptunian satellites range in diameter from 58 to 416 km (36 to 258 miles).

Apart from Triton, the moons of Neptune are irregularly shaped and have very

dark surfaces.

Triton is the largest moon of Neptune, with a diameter of 2,700 kilometers

(1,680 miles). It was discovered by William Lassell, a British astronomer, in

1846 scarcely a month after Neptune was discovered. Triton is colder than any

other measured object in the Solar System with a surface temperature of -235? C

(-391? F). It has an extremely thin atmosphere. Nitrogen ice particles might

form thin clouds a few kilometers above the surface. The atmospheric pressure at

Triton’s surface is about 14 microbars, 1/70,000th the surface pressure on Earth.

Triton is the only large satellite in the solar system to circle a planet in a

retrograde direction — in a direction opposite to the rotation of the planet.

It also has a density of about 2.066 grams per cubic centimeter (the density of

water is 1.0 gram per cubic centimeter). This means Triton contains more rock

in its interior than the icy satellites of Saturn and Uranus do. The relatively

high density and the retrograde orbit has led some scientists to suggest that

Triton may have been captured by Neptune as it traveled through space several

billion years ago. If that is the case, tidal heating could have melted Triton

in its originally eccentric orbit, and the satellite might even have been liquid

for as long as one billion years after its capture by Neptune. Triton is scarred

by enormous cracks. Voyager 2 images showed active geyser-like eruptions spewing

nitrogen gas and dark dust particles several kilometers into the atmosphere.