Hubble spots spectacular auroras on ice giant Uranus

Nasa and the European Space Agency have released a stunning image showing auroras on Uranus.

This composite image of the giant icy planet was taken by Voyager 2, and combined with observations of the auroras captured by the Hubble space telescope.

Auroras can happen on planets other than Earth as long as they have an atmosphere and a magnetic field. They are caused by streams of charged particles originating from solar winds, moon volcanism or the planetary ionosphere.

When these particles become caught in magnetic fields and travel into the planet's atmosphere, they interact with atmospheric gases such as oxygen and nitrogen.

This interaction sets off the spectacular bursts of light that we call auroras.

Scientists have observed and studied auroras on Jupiter and Saturn for many years now, but their interest for Uranus' auroras is more recent, and many questions remain regarding the phenomenon.

But in 2011, the Nasa/ESA Hubble Space Telescope became the first Earth-based telescope to capture an image of the auroras on Uranus.

In 2012 and 2014, astronomers took another look at the auroras, this time using the ultraviolet capabilities of the Space Telescope Imaging Spectrograph (STIS) on Hubble.

This research led to an in-depth observation of auroras on Uranus, as the scientists studied the effects of two powerful bursts of solar wind travelling from the sun to the planet. They were able to observe the most intense auroras ever seen on Uranus and found out that they rotated with the planet.

This work on auroras also allowed the researchers to identify the planet magnetic field and to re-discover its magnetic poles – due to uncertainties in measurements, they had previously lost track of them after their discovery by Voyager 2 in 1986.

The new images of the auroras on Uranus will continue to enrich scientists' knowledge of the impressive phenomenon.