Scientists confirm the existence of water in the atmosphere of a gas giant

The researchers found strong evidence of water on a young gas giant outside our solar system.

The planet HR 8799c has a mass of about 7 masses of Jupiter and revolves around its star host every 200 years. Its atmospheric composition shows that water is likely to be a major component of the planet. However, it lacks methane. The findings come from a new analysis of observations made by state-of-the-art instruments on the W.M. Keck Observatory at Maunakea, Hawaii.

The planet HR 8799c has been observed several times, but the presence of water in its atmosphere has never been detected before. By combining the new data with a technique called adaptive optics, researchers have removed the blur effect of the planet and created the most detailed study ever done on its atmosphere. The technique has implications for the search for life beyond the Earth.

"This type of technology is exactly what we want to use in the future to look for signs of life on a planet similar to the Earth, we are not there yet but we are moving forward." Dimitri Mawet, professor of astronomy at Caltech and a researcher at NASA JPL said in a statement.

Located about 129 light-years from Earth, the HR 8799c and three of its companions were the only multiple-planet system to be confirmed by the direct imaging technique. Taking direct pictures of planets in orbit around other stars is a daunting task, as light from host stars surpasses planets and makes them hard to see.

Once the image is obtained, astronomers can use instruments, called spectrometers, to separate the light from the planet and measure the chemical footprints of the atmosphere. Until now, this strategy has been used to better understand the atmosphere of several giant exoplanets, which was not possible before.

The ultimate goal is to search for chemicals in the atmospheres of Earth-like planets that revolve around the "habitable zone" of the star – the distance in which the surface temperature allows liquid water. Exoplanets of the terrestrial type are currently our best candidates to house life.

Ji Wang, lead author of the study, says. "For now, with Keck, we can already learn about the physics and dynamics of these giant exotic planets, which look nothing like our own planets in the solar system."