Solar System Sun
Terrestrial Planet Mercury, Venus, Earth (Moon), Mars
Asteroid Belt Ceres, Vesta
Jovian Planet Jupiter, Saturn, Uranus, Neptune
Kuiper Belt Pluto, Haumea, Makemake
Scattered Disc Eris, Sedna, Planet X
Oort Cloud Etc. Scholz’s Star
Small Body Comet, Centaur, Asteroid
These are organized by a classification scheme developed exclusively for Cosma. More…
Neptune : the planet eighth in order from the sun — Webster
Neptune is the eighth and farthest known planet from the Sun in the Solar System. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. 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 and slightly larger than Neptune. Neptune orbits the Sun once every 164.8 years at an average distance of 30.1 astronomical units (4.50×109 km). It is named after the Roman god of the sea and has the astronomical symbol ♆, a stylised version of the god Neptune’s trident.
Neptune is not visible to the unaided eye and is the only planet in the Solar System 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 with a telescope on 23 September 1846 by Johann Galle within a degree of the position predicted by Urbain Le Verrier. Its largest moon, Triton, was discovered shortly thereafter, though none of the planet’s remaining known 14 moons were located telescopically until the 20th century. The planet’s distance from Earth gives it a very small apparent size, making it challenging to study with Earth-based telescopes. Neptune was visited by Voyager 2, when it flew by the planet on 25 August 1989. The advent of the Hubble Space Telescope and large ground-based telescopes with adaptive optics has recently allowed for additional detailed observations from afar.
Neptune’s composition can be compared and contrasted with the Solar System’s other giant planets. Like Jupiter and Saturn, Neptune’s atmosphere is composed primarily of hydrogen and helium, along with traces of hydrocarbons and possibly nitrogen, but it contains a higher proportion of “ices” such as water, ammonia, and methane. However, its interior, like that of Uranus, is primarily composed of ices and rock, which is why Uranus and Neptune are normally considered “ice giants” to emphasise this distinction. Traces of methane in the outermost regions in part account for the planet’s blue appearance.
In contrast to the hazy, relatively featureless atmosphere of Uranus, Neptune’s atmosphere has active and visible weather patterns. For example, at the time of the Voyager 2 flyby in 1989, the planet’s southern hemisphere had 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 kilometres per hour (580 m/s; 1,300 mph). 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 55 K (−218 °C). Temperatures at the planet’s center are approximately 5,400 K (5,100 °C). Neptune has a faint and fragmented ring system (labelled “arcs”), which was first detected during the 1960s and confirmed by Voyager 2. — Wikipedia
Neptune News -- ScienceDaily Planet Neptune News. Read astronomy articles on Neptune's oddball moon Triton. See images of Neptune and more.
Astronomers find 'Forbidden' planet in 'Neptunian...
on May 28, 2019 at 11:30 pm
An exoplanet smaller than Neptune with its own atmosphere has been discovered in a region close to its star where no Neptune-sized planets would normally be found. […]
Neptune's moon Triton fosters rare icy union
on May 22, 2019 at 6:17 pm
Astronomers using the Gemini Observatory explore Neptune's largest moon Triton and observe, for the first time beyond the lab, an extraordinary union between carbon monoxide and nitrogen ices. The discovery offers insights into how this volatile mixture can transport material across the moon's surface via geysers, trigger seasonal atmospheric changes, and provide a context for conditions on other distant, icy worlds. […]
TESS finds its first Earth-sized planet
on April 15, 2019 at 4:23 pm
A nearby system hosts the first Earth-sized planet discovered by NASA's Transiting Exoplanets Survey Satellite, as well as a warm sub-Neptune-sized world. This milestone sets the path for finding smaller planets around even smaller stars, and those planets may potentially be habitable. […]
Hubble captures birth of giant storm on Neptune
on March 25, 2019 at 4:03 pm
Images taken by the Hubble Space Telescope document the formation of a Great Dark Spot on Neptune for the first time, report researchers in a new study. […]
Icy giant planets in the laboratory
on March 25, 2019 at 3:02 pm
Giant planets like Neptune may contain much less free hydrogen than previously assumed. Researchers drove shock waves through two different types of plastic to reach the same temperatures and pressures present inside such planets, and observed the behavior using ultra-strong X-ray laser pulses. Unexpectedly, one of these plastics kept its crystalline structure even at the most extreme pressures. Since the icy giant interiors are made up of the same components as the plastic, planetary models […]
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Astronomers see 'warm' glow of Uranus' rings
on June 20, 2019 at 6:00 pm
The rings of Uranus are invisible to all but the largest telescopes—they weren't even discovered until 1977—but they're surprisingly bright in new heat images of the planet taken by two large telescopes in the high deserts of Chile. […]
Starshade would take formation flying to extremes
on June 12, 2019 at 12:26 pm
Anyone who's ever seen aircraft engaged in formation flying can appreciate the feat of staying highly synchronized while airborne. In work sponsored by NASA's Exoplanet Exploration Program (ExEP), engineers at the Jet Propulsion Laboratory in Pasadena, California, are taking formation flying to a new extreme. […]
Dynamic compression provides new insight into...
on June 5, 2019 at 12:21 pm
Crystal growth is a crucial issue for fundamental science and wide applications. The growth morphology and speed are generally determined by an interplay between macroscopic thermodynamic driving forces and the microscopic kinetic process at crystal-liquid interface. […]
A pair of fledgling planets directly seen growing...
on June 3, 2019 at 3:54 pm
Astronomers have directly imaged two exoplanets that are gravitationally carving out a wide gap within a planet-forming disk surrounding a young star. While over a dozen exoplanets have been directly imaged, this is only the second multi-planet system to be photographed. (The first was a four-planet system orbiting the star HR 8799.) Unlike HR 8799, though, the planets in this system are still growing by accreting material from the disk. […]
The 'Forbidden' planet has been found in the...
on May 29, 2019 at 6:52 am
An exoplanet smaller than Neptune with its own atmosphere has been discovered in the Neptunian Desert, by an international collaboration of astronomers, with the University of Warwick taking a leading role. […]