Webb telescope detects water vapour around a rocky planet with stronger gravity than Earth

Using the Near-Infrared Spectrograph (NIRSpec) instrument on the James Webb Space Telescope, astronomers studied a rocky exoplanet called GJ 486 b. Surprisingly, water vapour was detected around the rocky world, but, it's uncertain if the water vapour is actually from the planet or its host star.

GJ 486 b is three times as massive as Earth and orbits a red dwarf star once every two Earth days. The planet is too close to its star to be within the habitable zone and its surface temperature is about 430 degrees Celsius, which is far too hot to support life as we know it on Earth.

The presence of water vapour around GJ 486 b, if associated with the planet, would suggest the existence of an atmosphere despite the planet's extremely high temperature and close orbit around its host star.

Water vapour has been observed in the atmospheres of gaseous exoplanets, before, but no atmosphere has been detected around a rocky exoplanet.

The team behind this discovery cautions that the water vapor detected could be associated with cool starspots on the star itself, rather than with the planet. Starspots are cooler than the surrounding area, therefore water vapour would concentrate there, according to the researchers.

"While the water vapour could potentially indicate the presence of an atmosphere on GJ 486 b, an equally plausible explanation is water vapour from the star. The planet's host star is cool enough that water vapour can exist in its photosphere," the European Space Agency wrote in a post.

If the planet has an atmosphere, in that case, it would need to be constantly replenished by volcanic activity that ejects steam from the planet's interior. To confirm the presence of water in the planet's atmosphere, further observations are necessary to determine the exact amount of water that may be present.

📷 The NASA/ESA/CSA James #Webb Space Telescope has found hints of water vapor around the rocky exoplanet GJ 486 b. 💧 If the water vapor is associated with the planet, it could indicate that it has an atmosphere despite its scorching temperature and close proximity to its… pic.twitter.com/1a0Qd0oCWd

— ESA (@esa) May 1, 2023