Astronomers have detected water in the atmosphere of a planet 179 light years away in the hunt for alien life.

A team at the Keck Observatory in Maunakea, Hawaii made the discovery when investigating HR 8799c - a gas planet seven times the size of Jupiter.

The planet, one of four which orbit the star HR 8799, was found 179 light years away in the constellation Pegasus.

A team at the Keck Observatory in Maunakea, Hawaii made the discovery when investigating HR 8799c - a giant gas planet seven times the size of Jupiter

Astronomers used state-of-the-art instrumentation to confirm the existence of water and a lack of methane in the planet's atmosphere.

The team combined high-resolution spectroscopy with a technique known as adaptive optics, which corrected the blurring effect of Earth’s atmosphere.

Once a photograph was taken of the planet, astronomers then used instruments called spectrometers to break apart the planet's light.

This revealed a fingerprint of the chemicals in the atmosphere - a feat possible due to a spectrometer on the Keck 2 telescope called the Near-Infrared Cryogenic Echelle Spectrograph (NIRSPEC).

'This type of technology is exactly what we want to use in the future to look for signs of life on an Earth-like planet,' said Dimitri Mawet, an associate professor of astronomy at Caltech.

'We aren’t there yet but we are marching ahead.'

Though astronomers have photographed more than a dozen exoplanets, HR 8799 is so-far the only multi-planet solar system to have had its picture taken.

The planet, one of four which orbit the star HR 8799, was found 179 light years away in the constellation Pegasus

Experts now hope to repeat the process on smaller planets which are closer to their stars.

The goal, scientists at the Keck Observatory wrote, is to look for chemicals signaling a habitable atmosphere for life on Earth-like planets such as water, oxygen and methane.

It is hoped this will be realised with the upcoming Thirty Meter Telescope - a giant instrument planned for the late 2020s.

Ji Wang, the lead author of a Astronomical Journal paper on the findings, said: 'Right now, with Keck, we can already learn about the physics and dynamics of these giant exotic planets, which are nothing like our own solar system planets.

'We are now more certain about the lack of methane in this planet. This may be due to mixing in the planet’s atmosphere.

'The methane, which we would expect to be there on the surface, could be diluted if the process of convection is bringing up deeper layers of the planet that don’t have methane.'