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04 August 2017

Neptune is experiencing a 9000km-wide storm, spanning one third of its hemisphere

SOMETHING strange is happening on Neptune.

A colossal storm has taken hold of its equator, and now spans about one third of the blue planet’s radius.

When the space probe Voyager 2 flew past Neptune in the 1980s, the bright blue orb was seen to have its own complex weather patterns.

Now, observations from the Keck Observatory in Hawaii are showing something weird.

An colossal wild storm is surging across the blue planet’s equator.

It’s already almost as wide as the Earth — 9000km. It’s likely to be hailing methane ice deep into the planet’s interior.

Observations of a colossal 900km-wide storm spanning Neptune's equator from the Keck Observatory in Hawaii.

Observations of a colossal 900km-wide storm spanning Neptune’s equator from the Keck Observatory in Hawaii.Source:Supplied

“This one is weird, because it’s really big and it’s not dark. It’s bright, and the bright stuff is probably sort of like cirrus clouds on top of a thunderstorm that’s underneath,” Bryan Butler of the National Radio Astronomy Observatory told National Geographic. “And it seems to be staying steady, for it’s been a month or something now.”

While the ‘enormous white blob’ is impressive, it still has some way to go to challenge Jupiter’s Great Red Spot.

While Neptune’s storm is proportionally much larger, the planet itself is considerably smaller than Jupiter. The Great Red Spot — while steadily shrinking in recent decades — still tops out at 16,000km wide.

Neptune remains something of a mystery.

It orbits the Sun some 30 times further out than the Earth. And no space probe has visited it since Voyager 2 1989.

It has the fastest known winds in the Solar System: up to 1600km/h has been recorded at the equator.

Exactly where it gets the energy from to fuel this severe weather is not known. It receives just one thousandth of the sunlight Earth does. Temperatures average -214C.

So a storm of this intensity and size is doubly weird.

“Seeing a storm this bright at such a low latitude is extremely surprising,” says Ned Molter, a graduate student at University of California, Berkeley, who spotted the storm late last month.

Neptune's enormous storm is likely to be hailing methane.

Neptune’s enormous storm is likely to be hailing methane.Source:Supplied

“Normally, this area is really quiet and we only see bright clouds in the mid-latitude bands, so to have such an enormous cloud sitting right at the equator is spectacular.”

Astronomers say they believe a collosal dark vortex deep inside Neptune’s atmosphere may be generating the cloud cover. Gases cool as the vortex churns them upwards. Once they condense, they form clouds.

It’s a process very much like that which produces rain on Earth. On Neptune, however, it’s most likely to be methane.

“This big vortex is sitting in a region where the air, overall, is subsiding rather than rising,” says Professor Imke de Pater of UC Berkeley’s Astronomy Department. “Moreover, a long-lasting vortex right at the equator would be hard to explain physically.”

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