In 2016, scientists discovered seven planets orbiting an ultra cool dwarf star called TRAPPIST-1, raising hopes that they could harbour life .
Now, a new study has revealed that the seven planets are mostly rocky, with potentially more liquid water than Earth.
Researchers from the University of Bern found that some of the planets have up to five per cent of their mass in liquid water form – about 250 time more water than we have on Earth.
Speaking to Space.com , Dr Simon Grimm, who led the study, said: “All the TRAPPIST-1 planets are very Earth-like — they have a solid core, surrounded by an atmosphere.”
In particular, the researchers believe that planet TRAPPIST-1e could be a good candidate for life.
Dr Grimm added: “TRAPPIST-1e is the exoplanet which is most similar to Earth in terms of mass, radius and energy received from its star.”
To reach this conclusion, the researchers used a technique called transit-timing variations (TTVs).
This technique relies on the small variations in the amount of time it takes a planet to pass between its star and our viewpoint – called a transit.
TTVs allow scientists to make extremely sensitive observations about planetary masses and densities.
Dr Grimm explained: “Using TTVs is currently the only method to determine the masses and therefore the densities of planets like the TRAPPIST-1 system.”
The TTV analysis revealed that the densities of the planets ranges from 0.6 to 1.0 times Earth’s density.
And the seven planets are rich in water, with some water levels reaching as high as five per cent of the total mass.
The researchers hope their findings will help teams in the future to understand whether the planets could be capable of supporting life.
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