Astronomers have discovered seven Earth-sized planets orbiting a star just 40 light-years away. At least three of them could harbour oceans of water, increasing the possibility they could host life. This system has the largest number of Earth-sized planets yet found, making it a key object for future study.
In May 2016, Michaël Gillon and colleagues reported the detection of three exoplanets transiting an ultracool dwarf star called TRAPPIST-1, which is located 12 parsecs (about 39 light-years) from the Sun.
Motivated by this discovery, the authors conducted a monitoring campaign of the star from the ground and from space that allowed them to identify four additional planets in this system. Initial mass estimates suggest that the six inner planets have masses that are similar to the mass of Earth and probably have solid compositions.
The research, published in the journal Nature, brings the possible discovery of new worlds since 2015 — when planet Kepler-452b became first near-Earth-size world found in the habitable zone of a star similar to our sun — to 121.