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

Fall into an ice giant's atmosphere

The unique atmospheric compositions of "ice giant" planets Uranus and Neptune were recreated to simulate a plunge deep within them, using suitably adapted European shocktubes and plasma facilities.

The clouds on Neptune perform a surprise disappearing act

For the first time in nearly three decades of observations, clouds seen on Neptune have all but vanished. Images from 1994 to 2022 of the big blue planet captured from Maunakea on Hawaiʻi Island through the lens of W. M. ...

Redness of Neptunian asteroids sheds light on early solar system

Asteroids sharing their orbits with the planet Neptune have been observed to exist in a broad spectrum of red color, implying the existence of two populations of asteroids in the region, according to a new study by an international ...

New rare 'hot sub-Neptune' exoplanet discovered

Using NASA's Transiting Exoplanet Survey Satellite (TESS), an international team of astronomers has detected a new alien world. The newfound exoplanet, designated TOI-2196 b, turns out to be a type of a rare "hot sub-Neptune." ...

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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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