Planet not far from Earth could potentially be habitable ocean-planet

Approximately 50 light-years away from Earth lies the system LHS 1140, where two super-Earths were previously discovered. One of them holds promise as an ocean planet, potentially suitable for life. This was clarified with the help of the James Webb Space Telescope, whose instruments analyzed the atmosphere composition of the exoplanet LHS 1140b.

The NIRSpec instrument of the James Webb Space Telescope studied the atmosphere of exoplanet LHS 1140b in July 2023 during two transit events of the exoplanet across its star. Previously thought to be a rocky world with a mass exceeding 6 Earths, new observations have lowered the estimate of the exoplanet's mass and size to 5.6 Earth masses and a radius 1.73 times that of Earth. The planet's insolation is estimated to be at 0.42 times that of Earth, and the average surface temperature could be around 226 K. 

Furthermore, the planet LHS 1140b orbits a red dwarf with a mass of 0.18 solar masses. It is situated close enough to the star, but the weak radiation from the central luminary does not overheat its surface. This is crucial because for a planet with a global ocean, increased insolation would automatically trigger a greenhouse effect, leading to the demise of all life, as seen with the greenhouse effect on Venus.

In short, if LHS 1140b harbors a global ocean, the water temperature on its surface is above freezing point, indicating potential suitability for the emergence of biological life. However, judging from the size and density estimates of the exoplanet, instead of 10% water on its surface, a dense gaseous atmosphere might be present. Spectral analysis of the atmosphere and modeling have shown that the likelihood of a dense atmosphere on LHS 1140b is lower than the probability of a vast volume of water on its surface. Therefore, it is a good candidate for an ocean planet.