Neptune, furthest planet from the Sun is celebrating its first birthday. It has been known  to humans for only a single Neptunian year.

Image of neptune

Blue Planet: how appropriately named for a sea god! (Image credit: NASA)

Neptune, which is not visible with the naked eye, was discovered by mathematical prediction in 1846 before being observed through a telescope. Astronomers noticed that Uranus was not always in the expected position; therefore they assumed that the gravity of an unknown planet must have been influencing Uranus. John C. Adams (1819-1892) an English astronomer and French mathematician Urbain J.J. Le Verrier (1811-1877) are both credited with the discovery of Neptune by predicting where this new planet should be, although they completed their work independently unknown to one another. Johann G. Galle (1812-1910) director of Urania Observatory in Berlin confirmed their findings. Neptune takes its name from the Roman god of the sea and orbits at an average of 30 AU (2 793 million miles, 4 495 million km) from the Sun taking 164.8 years to complete a single circuit.

The majority of the Neptnian atmosphere is made of hydrogen and helium. Neptune’s blue colour is  due to the presence of methane. After the surprising discovery of rings around Uranus, astronomers began searching for Neptune’s rings. They discovered full but thin rings, which were a little lumpy and twisted, that are thought to be much younger than their planet.

Image of Triton and Neptune

Triton seen with its parent planet in a photomontage. (Image credit: NASA)

Neptune, rather unlike Uranus, has some very prominent features on its surface, dark spots showed Neptune to be a very stormy planet with wind speeds of more than 2000 km/h (1200 mph). These features appear and vanish frequently, unlike Jupiter’s Great Red Spot which has been prominent for a few hundred years. As well as being a windy planet, Neptune is also unusually quite warm. In 2007, astronomers using the Very Large Telescope (VLT) in Chile found that the planet’s south pole was 10⁰ C (18 ° F) warmer than anywhere else on the planet probably due to heat during the course of a prolonged summer.

Neptune’s largest moon Triton travels around the planet backwards, it is also the coldest large body in the Solar System with a temperature of 38K (-200⁰  C, -391 ° F). Tidal interactions between Neptune and Triton mean that in 100 million years these two bodies may come too close to one another causing Triton to be torn apart leaving Neptune with a ring system more spectacular than Saturn’s.

Neptune is a fairly recent additions to our Solar System. As our technology improves, and further probes are sent to this region of space, hopefully before its second birthday we will learn more about our ice giant neighbour.

Image of_Martina Redpath

Martina Redpath, ESO (Image credit: Armagh Planetarium)

(Article by Martina Redpath)


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