Five exoplanets show evidence of water vapour

The Hubble Space Telescope and some new imaging techniques have helped scientists detect traces of water vapour on five massive planets in our galactic backyard. However, despite the presence of water molecules in their atmospheres, none of these five planets is suitable to life. They are all gas giants, sometimes called hot-Jupiters, and they are all too close to their suns to sustain liquid water on their surfaces.

The planets -- WASP-17b, HD209458b, WASP-12b, WASP-19b and XO-1b -- are tidally locked with their stars so that the same side of the planet always faces the star and is constantly bombarded with a powerful stream of solar radiation. The heat from the star is distributed around the planet via strong winds that move faster than the speed of sound.

To find traces of water vapor in their atmospheres, L. Drake Deming, an astronomer at the University of Maryland, and his colleagues used Hubble's Wide Field Camera 3, which measures near-infrared light. The scientists waited until each planet was about to pass in front of its sun, then pointed Hubble at it. Because water molecules absorb certain wavelengths of light, the scientists could detect the presence of water vapour during the planet's transit across its sun if those wavelengths were not picked up by Hubble.

Hubble is only strong enough to see the signs of water vapor on the gas giant planets, but Deming said that Hubble's successor -- the James Webb Telescope, slated to launch in 2018 -- will be strong enough to find water signatures in the atmospheres of smaller, rockier planets more like Earth.

To know more about the exoplanets and the findings, click here.