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