Neptune is that the eighth and farthest well-known planet from the Sun within the system. within the system, it’s the fourth-largest planet by diameter, the third-most-massive planet, and also the densest big planet. Neptune is seventeen times the mass of Earth, slightly a lot of large than its near-twin Uranus. Neptune is denser and physically smaller than Uranus as a result of its bigger mass causes a lot of attraction compression of its atmosphere. Neptune orbits the Sun once each 164.8 years at a mean distance of 30.1 AU (4.5 billion km). it’s named when the Roman god of the ocean and has the astronomical image ♆, a stylized version of the god Neptune’s shaft.
Neptune isn’t visible to the unaided eye and is that the solely planet within the system found by mathematical prediction instead of by empirical observation. sudden changes within the orbit of Uranus LED Alexis Bouvard to deduce that its orbit was subject to attraction perturbation by associate degree unknown planet. Neptune was later on ascertained with a telescope on twenty three Gregorian calendar month 1846 by Johann Galle among a degree of the position foreseen by Urbain autoimmune disease Verrier. Its biggest moon, Triton, was exposed not long, and none of the planet’s remaining well-known thirteen moons were set telescopically till the twentieth century. The planet’s distance from Earth offers it a awfully little apparent size, creating it difficult to review with Earth-based telescopes. Neptune was visited by traveler two, once it flew by the earth on twenty five August 1989. the arrival of the Edwin Hubble house Telescope and enormous ground-based telescopes with adaptational optics has recently allowed for extra careful observations from afar.
Like Jupiter and Saturn, Neptune’s atmosphere consists primarily of H and element, in conjunction with traces of hydrocarbons and presumably chemical element, although it contains the next proportion of “ices” like water, ammonia, and alkane. However, the same as Uranus, its interior is primarily composed of ices and rock; Uranus and Neptune area unit usually thought-about “ice giants” to stress this distinction. Traces of alkane within the outer regions partially account for the planet’s blue look.
In distinction to the hazy, comparatively plain atmosphere of Uranus, Neptune’s atmosphere has active and visual weather patterns. for instance, at the time of the traveler two flyby in 1989, the planet’s hemisphere had an excellent Dark Spot equivalent to the good Red Spot on Jupiter. These weather patterns unit driven by the strongest sustained winds of any planet inside the system, with recorded wind speeds as high as two,100 km/h (580 m/s; one,300 mph). attributable to its nice distance from the Sun, Neptune’s outer atmosphere is one among the coldest places within the system, with temperatures at its cloud crack approaching fifty five K (−218 °C; −361 °F). Temperatures at the planet’s centre area unit roughly 5,400 K (5,100 °C; 9,300 °F). Neptune incorporates a faint and fragmented ring system (labelled “arcs”), that was discovered in 1984, then later confirmed by voyager two.
