Precise measurements reveal that the exoplanets have remarkably similar densities, which provides clues about their composition.

PASADENA, Calif. (NASA PR) — The red dwarf star TRAPPIST-1 is home to the largest group of roughly Earth-size planets ever found in a single stellar system. Located about 40 light-years away, these seven rocky siblings provide an example of the tremendous variety of planetary systems that likely fill the universe.