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Neptune System

Normally the eighth planet from the Sun, although the dwarf planet Pluto, because of its elongated orbit, occasionally comes closer for periods of 20 years around its perihelion. Neptune is the most distant of the gas giants. It is also marginally the smallest of the gas giants in the solar system, after Uranus, although its volume is still 60 times greater than that of the Earth and it is slightly more massive than Uranus. Neptune and Uranus are more appropriately referred to as ice giants because their composition is substantially different from that of Jupiter and Saturn. Neptune was discovered in 1846 by Johann Galle and Louis d'Arrest following predictions by Urbain Leverrier.
Neptune's deep atmosphere extends 10-20% of the way to the center of the planet. At high altitudes it consists mostly of hydrogen (80%) and helium (19%). Increasing concentrations of methane, other hydrocarbons (including ethane, acetylene, and diacetylene), ammonia, and water vapor occur in the dark, warmer, lower regions of the atmosphere. Finally the atmosphere blends into the superheated liquid interior. Neptune has 13 known moons.

(For further details see Neptune »)

(Source: The Internet Encyclopedia of Science »)

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Triton’s Summer Sky of Methane and Carbon Monoxide Last Updated on 2010-04-05 00:00:00 GARCHING, Germany (April 6, 2010) – According to the first ever infrared analysis of the atmosphere of Neptune's moon Triton, summer is in full swing in its southern hemisphere. The European observing team used ESO's Very Large Telescope and discovered carbon monoxide and made the first ground-based detection of methane in Triton's thin atmosphere. These observations revealed that the thin atmosphere varies seasonally, thickening when warmed. "We have found real evidence that the Sun still makes its presence felt on Triton, even from so far away. This icy moon actually has seasons just as we do on Earth, but they change far more slowly," says Emmanuel Lellouch, the lead author of the paper reporting these results in Astronomy & Astrophysics. On Triton, where the average surface temperature is about minus 235 degrees Celsius, it is currently summer in the... More »
Neptune - Details Last Updated on 2009-03-17 00:00:00 Neptune is normally the eighth planet from the Sun, although the dwarf planet Pluto, because of its elongated orbit, occasionally comes closer for periods of 20 years around its perihelion. Neptune is the most distant of the gas giants. It is also marginally the smallest of the gas giants in the solar system, after Uranus, although its volume is still 60 times greater than that of the Earth and it is slightly more massive than Uranus. Neptune and Uranus are more appropriately referred to as ice gi because their composition is substantially different from that of Jupiter and Saturn. Neptune was discovered in 1846 by Johann Galle and Louis d’Arrest following predictions by Urbain Leverrier. In fact, Galileo Galilei, as his notes reveal, had seen Neptune much earlier, in 1612 and again in 1613, but thought it was a star. The name "Neptune," after the Roman god of the sea, was first... More »
Neptune - Overview Last Updated on 2008-12-22 00:00:00 Neptune is the eighth planet from the Sun, and was the first planet located through mathematical predictions rather than through regular observations of the sky. (Galileo had recorded it as a fixed star during observations with his small telescope in 1612 and 1613.) When Uranus didn't travel exactly as astronomers expected it to, a French mathematician, Urbain Joseph Le Verrier, proposed the position and mass of another as yet unknown planet that could cause the observed changes to Uranus' orbit. After being ignored by French astronomers, Le Verrier sent his predictions to Johann Gottfried Galle at the Berlin Observatory, who found Neptune on his first night of searching in 1846. Seventeen days later, its largest moon, Triton, was also discovered. Nearly 4.5 billion kilometers (2.8 billion miles) from the Sun, Neptune orbits the Sun once every 165 years. It is invisible to the naked eye... More »