"We are only beginning to discover the true complexity of these worlds."
The hunt is on for terrestrial exoplanets in habitable zones, and some of the most promising candidates were discovered almost a decade ago about 40 light-years from Earth. The TRAPPIST-1 system contains seven terrestrial planets similar to Earth, and four of them may be in the habitable zone. The star is a dim red dwarf, so the habitable zone is close to the star, and so are the planets. For that reason, astronomers expect them to be tidally-locked to the star.

