Neptune

**Neptune** is the aicht an farthest planet frae the Sun in the Solar Seestem. It is the fowert-lairgest planet bi diameter an the third-lairgest bi mass. Amang the gaseous planets in the solar seestem, Neptune is the maist dense. Neptune is 17 times the mass o Yird an is slichtly mair massive than its near-twin Uranus, which is 15 times the mass o Yird but nae as dense. On average, Neptune orbits the Sun at a distance o 30.1 AU, approximately 30 times the Yird–Sun distance. Named for the Roman god o the sea, its astronomical seembol is , a stylised version o the god Neptune's trident.

Neptune wis the first planet foond bi mathematical prediction rather than bi empirical observation. Unexpectit chynges in the orbit o Uranus led Alexis Bouvard tae deduce that its orbit wis subject tae gravitational perturbation bi an unkent planet. Neptune wis subsequently observed on 23 September 1846 bi Johann Galle within a degree o the poseetion predictit bi Urbain Le Verrier, an its lairgest muin, Triton, wis discovered shortly thareefter, tho none o the planet's remainin 13 muins wur locatit telescopically till the 20t century. Neptune haes been visited bi anly ane spacecraft, *[[Voyager 2]]*, which flew bi the planet on 25 August 1989.

Neptune is seemilar in composeetion tae Uranus, an baith hae composeetions which differ frae those o the lairger gas giants, Jupiter, an Saturn. Neptune's atmosphere, while seemilar tae Jupiter's an Saturn's in that it is componed primarily o hydrogen an helium, alang wi traces o hydrocarbons an possibly nitrogen, contains a heicher proportion o "ices" sic as watter, ammonia, an methane. Astronomers whiles categorise Uranus an Neptune as "ice giants" in order tae emphasise thir distinctions. The interior o Neptune, lik that o Uranus, is primarily componed o ices an rock. It is possible that the cor haes a solit surface, but the temperatur wad be thoosands o degrees an the atmospheric pressur crushin. Traces o methane in the ootermaist regions in pairt accoont for the planet's blue appearance.

In contrast tae the hazy, relatively featureless atmosphere o Uranus, Neptune's atmosphere is notable for its active an veesible wather patterns. For example, at the time o the 1989 *Voyager 2* flyby, the planet's soothren hemisphere possessed a Great Dark Spot comparable tae the Great Red Spot on Jupiter. Thir wather patterns are driven bi the strangest sustained winds o ony planet in the Solar Seestem, wi recordit wind speeds as heich as . Acause o its great distance frae the Sun, Neptune's ooter atmosphere is ane o the cauldest places in the Solar Seestem, wi temperaturs at its clood taps approachin . Temperaturs at the planet's centre are approximately . Neptune haes a faunt an fragmented ring seestem (labeled 'arcs'), which mey hae been detectit durin the 1960s but wis anly indisputably confirmed in 1989 bi *Voyager 2*.

## Notes


## References

## Freemit airtins

* NASA's Neptune fact sheet 
* Neptune frae Bill Arnett's nineplanets.org
* Neptune Astronomy Cast episode No. 63, includes full transcript.
* Neptune Profile  at NASA's Solar Seestem Exploration steid
* Planets&nbsp;– Neptune  A childer's guide tae Neptune.