TRAPPIST-1e is a rocky, close-to-Earth-sized exoplanet orbiting within the habitable zone around the ultra-cool red dwarf star TRAPPIST-1, located 40.7 light-years away from Earth in the constellation of Aquarius. Astronomers used the transit method to find the exoplanet, a method that measures the dimming of a star when a planet crosses in front of it.