Related topics: solar system · planets · orbit · jupiter · saturn

Hubble reveals dynamic atmospheres of Uranus, Neptune

During its routine yearly monitoring of the weather on our solar system's outer planets, NASA's Hubble Space Telescope has uncovered a new mysterious dark storm on Neptune and provided a fresh look at a long-lived storm circling ...

Encouraging prospects for moon hunters

Astrophysicists of the University of Zürich, ETH Zürich and the NCCR PlanetS show how the icy moons of Uranus were born. Their result suggests that such potentially habitable worlds are much more abundant in the Universe ...

Hubble sees Neptune's mysterious shrinking storm

Three billion miles away on the farthest known major planet in our solar system, an ominous, dark storm - once big enough to stretch across the Atlantic Ocean from Boston to Portugal - is shrinking out of existence as seen ...

Scientists predict Neptune's chemical make-up

Scientists have helped solve the mystery of what lies beneath the surface of Neptune – the most distant planet in our solar system. A new study sheds light on the chemical make-up of the planet, which lies around 4.5 billion ...

Kepler has taught us that rocky planets are common

Rocky planets are probably a whole lot more common in our galaxy than astronomers previously believed—according to the latest release of Kepler Space Telescope data last week—a scenario that enhances the prospects for ...

NASA completes study of future 'ice giant' mission concepts

A NASA-led and NASA-sponsored study of potential future missions to the mysterious "ice giant" planets Uranus and Neptune has been released—the first in a series of mission studies NASA will conduct in support of the next ...

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Neptune

Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times the mass of Earth but not as dense. On average, Neptune orbits the Sun at a distance of 30.1 AU, approximately 30 times the Earth–Sun distance. Its astronomical symbol is ♆, a stylized version of the god Neptune's trident.

Discovered on September 23, 1846, Neptune was the first planet found by mathematical prediction rather than by empirical observation. Unexpected changes in the orbit of Uranus led Alexis Bouvard to deduce that its orbit was subject to gravitational perturbation by an unknown planet. Neptune was subsequently observed by Johann Galle within a degree of the position predicted by Urbain Le Verrier, and its largest moon, Triton, was discovered shortly thereafter, though none of the planet's remaining 12 moons were located telescopically until the 20th century. Neptune has been visited by only one spacecraft, Voyager 2, which flew by the planet on August 25, 1989.

Neptune is similar in composition to Uranus, and both have compositions which differ from those of the larger gas giants, Jupiter and Saturn. Neptune's atmosphere, while similar to Jupiter's and Saturn's in that it is composed primarily of hydrogen and helium, along with traces of hydrocarbons and possibly nitrogen, contains a higher proportion of "ices" such as water, ammonia and methane. Astronomers sometimes categorize Uranus and Neptune as "ice giants" in order to emphasize these distinctions. The interior of Neptune, like that of Uranus, is primarily composed of ices and rock. Traces of methane in the outermost regions in part account for the planet's blue appearance.

In contrast to the relatively featureless atmosphere of Uranus, Neptune's atmosphere is notable for its active and visible weather patterns. For example, at the time of the 1989 Voyager 2 flyby, the planet's southern hemisphere possessed a Great Dark Spot comparable to the Great Red Spot on Jupiter. These weather patterns are driven by the strongest sustained winds of any planet in the Solar System, with recorded wind speeds as high as 2,100 km/h. Because of its great distance from the Sun, Neptune's outer atmosphere is one of the coldest places in the Solar System, with temperatures at its cloud tops approaching −218 °C (55 K). Temperatures at the planet's centre are approximately 5,400 K (5,000 °C). Neptune has a faint and fragmented ring system, which may have been detected during the 1960s but was only indisputably confirmed in 1989 by Voyager 2.

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