Potential ocean worlds outside the Solar System

Planets in the TRAPPIST-1 system

The popular TRAPPIST-1 system – with its seven Earthsized planets – became even more popular in 2017 when astronomers announced that they could be harbouring liquid water. Three of the planets reside in the star’s habitable zone, suggesting they would be the most likely objects of interest.

GJ 1214 b

GJ 1214 b is considered a super-Earth: it is 2.7 times Earth’s radius. It’s thought it could be surrounded in a steamy atmosphere. This potential ocean world was first discovered in 2009, but research has revealed that the exoplanet’s density is closer to water as opposed to Earth’s rocky density, which is much greater.

Kepler-22b

This exotic exoplanet has been described by NASA as a “super-Earth that could be covered in a super ocean”. This remark is based on the fact that this planet, which is 2.4-times larger than Earth, resides in the habitable zone around a star very similar to the Sun. This implies that it could have a similar evolutionary history to Earth.

Kepler-62f

Located 1,207 light years away in the constellation Lyra, Kepler-62f is a planet 40 per cent larger than Earth and sits in the habitable zone of its host star. A 2016 study of Kepler-62f found that there are multiple atmospheric compositions that allow it to stay warm enough to sustain liquid water.