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Astronomers have captured storms raging on the normally bland face of Uranus - although the origin of the storms remains a mystery.

The storms were first spotted back in August but more recent images have revealed they are still occurring.

And the cloud activity is so bright that even amateur astronomers have seen signs of it in the blue-green atmosphere of the planet, which is 30 times further away from the Sun than the Earth.

These are infrared images of Uranus obtained on 6 August 2014 with the Keck telescope in Hawaii. The white spot is an extremely large storm that was brighter than any feature ever recorded on the planet

Astronomers observing Uranus with the Keck Telescope in Hawaii detected eight large storms in the planet's northern hemisphere on August 5 and 6.

One was the brightest ever measured on Uranus, accounting for 30 per cent of all light reflected by the rest of the planet at a wavelength of 2.2 microns.

This is the 'colour' of light that senses clouds just below the tropopause, where the atmospheric pressure is half what it is at the Earth's surface.

Later observations by amateur astronomers revealed a bright spot, which scientists believe is evidence of storm activity much deeper in the atmosphere.

But interestingly, the extremely bright storm seen by Keck in the near infrared is not the one seen by the amateurs, which is much deeper in the atmosphere than the one that initially caused all the excitement.

Is is thought this feature is below the uppermost cloud layer of methane-ice in Uranus's atmosphere.

French amateur astronomer Marc Delcroix processed the amateur images and confirmed the discovery of a bright spot on an image by French amateur Régis De-Bénedictis, then in others taken by fellow amateurs in September and October.

He had his own chance on 3 and 4 October to photograph it with the Pic du Midi one-meter telescope, where on the second night, 'I caught the feature when it was transiting, and I thought, "Yes, I got it!"' said Delcroix.

'I was thrilled to see such activity on Uranus. Getting details on Mars, Jupiter or Saturn is now routine, but seeing details on Uranus and Neptune are the new frontiers for us amateurs and I did not want to miss that.

'I was so happy to confirm myself these first amateur images on this bright storm on Uranus, feeling I was living a very special moment for planetary amateur astronomy.'

These optical images of Uranus were taken on 19 September and 2 October, showing the dramatic appearance of a bright storm on a planet that normally displays only a diffuse bright polar region

A total solar eclipse hangs in the sky over the W. M. Keck Observatory on 11 July 1991, and the Nasa Infrared Telescope Facility is seen in the background. The edge of the Moon's shadow can be seen near the horizon

The findings were first presented at a meeting of the American Astronomical Society's Division of Planetary Sciences in Tucson, Arizona. 

Co-investigator Dr Heidi Hammel, from the US Space Science Institute, who was part of the initial observation in August said: 'This type of activity would have been expected in 2007, when Uranus's once every 42-year equinox occurred and the sun shined directly on the equator.

'But we predicted that such activity would have died down by now. Why we see these incredible storms now is beyond anybody's guess.'

Uranus has a diameter four times that of Earth and is wrapped in an atmosphere of hydrogen and helium, plus a dash of methane that gives it a blue tint. 

Because it is so distant - 30 times farther from the sun than Earth - astronomers were able to see little detail on its surface until adaptive optics on the Keck telescopes revealed features much like those on Jupiter.

 Bright clouds are probably caused by gases such as methane rising in the atmosphere and condensing into highly reflective clouds of methane ice.

Because Uranus has no internal source of heat, its atmospheric activity was thought to be driven solely by sunlight, which is now weak in the northern hemisphere. Hence astronomers were surprised when these observations showed such intense activity.