It’s not just Earth that has a decent light show: Scientists capture auroras in the atmosphere above Uranus

By Daily Mail Reporter

Published: 06:24 EST, 17 April 2012 | Updated: 07:24 EST, 17 April 2012

Scientists have captured images of auroras above the planet Uranus for the first time.

Detected by carefully scheduling observations from the Hubble Space Telescope, the Uranian light show consisted of short-lived, faint, glowing dots - a world of difference from the colourful curtains of light that often ring Earth's poles.

In the new observations the researchers detected the luminous spots twice on the dayside of Uranus - the side that's visible from Hubble.

Faint and brief: Interstellar tourists, travelling the 2.5billion miles from Earth to Uranus, may be a little disappointed if they went there to see an aurora. The Uranian versions are smaller and do not last as long as those on Earth

Faint aurora: The Hubble telescope picked up bright but brief aurora above the distant planet last year. Scientists believe larger aurora may be visible on the 'dark' (non-Earth-facing) side

Previously, the distant aurora had only been measured using instruments on a passing spacecraft.

Unlike auroras on Earth, which can turn the sky greens and purples for hours, the newly detected auroras on Uranus appeared to only last a couple minutes.

In general, auroras are a feature of the magnetosphere, the area surrounding a planet that is controlled by its magnetic field and shaped by the solar wind, a steady flow of charged particles emanating from the sun.

Different view: In this 2006 photo of Uranus, the bright dot is actually Ariel, one of the planet's 27 satellites. The moon's shadow can also be seen on the planet's cloud cover

Auroras are produced in the atmosphere as charged solar wind particles accelerate in the magnetosphere and are guided by the magnetic field close to the magnetic poles - that's why the Earthly auroras are found around high latitudes.

But contrary to the Earth - or even Jupiter and Saturn - the magnetosphere of Uranus is very poorly known, according to astronomer Laurent Lamy, of the Observatoire de Paris in Meudon, France, who led the new research.

The results from his team, which includes researchers from Britain, France and the United States, were published in the journal Geophysical Research Letters.

Auroras on Uranus are fainter than they are on Earth, and the planet is more than 2.5 billion miles away. Previous Earth-bound attempts to detect the faint auroras were inconclusive.

Astronomers got their last good look at Uranian auroras 25 years ago when the Voyager 2 spacecraft whizzed past the planet.

Dr Lamy added: 'This planet was only investigated in detail once, during the Voyager flyby, dating from 1986.

'Since then, we've had no opportunities to get new observations of this very unusual magnetosphere.'

Planetary scientists know that Uranus is an oddball among the solar system's planets when it comes to the orientation of its rotation axis.

Whereas the other planets resemble spinning tops, circulating around the Sun, Uranus is like a top that was knocked on its side - but still keeps spinning.

The researchers suspect that the unfamiliar appearance of the newly observed auroras is due to Uranus' rotational weirdness and peculiar traits of its magnetic axis.

Dramatic contrast: The Aurora Borealis - or Northern Lights - is the Earth's brightly coloured and long-lasting version of Uranian lights. Both are caused when solar wind reacts with the magnetic fields of the planets

Comparison: Charged particles high in the Earth's atmosphere also emit a red light. Scientists say they need further study of the Uranian version

The magnetic axis is both offset from the centre of the planet and lists at an angle of 60 degrees from the rotational axis - an extreme tilt compared to the 11 degree difference on Earth.

The 2011 auroras differ not only from Earth's auroras but also from the Uranian ones previously detected by Voyager 2.

When that spacecraft made its flyby decades ago, Uranus was near its solstice - its rotational axis was pointed toward the Sun.

In that configuration, the magnetic axis stayed at a large angle from the solar wind flow, producing a magnetosphere similar to the Earth's magnetosphere, although more dynamic.

Under those 1986 solstice conditions, the auroras lasted longer than the recently witnessed ones and were mainly seen on the nightside of the planet, similar to what's observed on Earth, Lamy said.

Hubble can't see the far side of the planet, however, so researchers don't know what types of auroras, if any, were generated there.

The new set of observations, however, is from when the planet was near equinox, when neither end of the Uranian rotational axis aims at the Sun, and the axis aligns almost perpendicular to the solar wind.

A better understanding of Uranus' magnetosphere could help scientists test their theories of how Earth's magnetosphere functions.