Evidence of water has been found in the atmosphere of a hot exoplanet located about 700 lightyears away. The exoplanet, named WASP-39b, is about the same mass as Saturn, but may have up to three times as much water.


Because WASP-39b has so much more water than Saturn, it must have formed in a different way. The amount of water suggests that the planet formed far away from its host star, where it could have been bombarded by icy material.

It then may have migrated inwards towards the host star, WASP-39, to end up in a close orbit, 20 times closer than Earth is to the Sun.

The team was able to split starlight that had passed through the exoplanet’s atmosphere, analyse it and find evidence of the presence of water.

The Hubble and Spitzer space telescopes were used to make the observations.

The astronomers hope that studying the exoplanet will help them learn more about how and where planets form around a star.

"We need to look outward so we can understand our own Solar System," says Hannah Wakeford of the Space Telescope Science Institute in Baltimore, lead investigator of the study.


"But exoplanets are showing us that planet formation is more complicated and more confusing than we thought it was. And that's fantastic!"


Elizabeth Pearson
Ezzy PearsonScience journalist

Ezzy Pearson is the Features Editor of BBC Sky at Night Magazine. Her first book about the history of robotic planetary landers is out now from The History Press.