7 planets orbiting a red dwarf star may be made of similar stuff Located about 40 light-years away, the red dwarf star, TRAPPIST-1 is home to the largest group of roughly Earth-size planets ever found in a single stellar system. Washington: The seven rocky planets orbiting the the red dwarf star TRAPPIST-1 have remarkably similar densities, which provides clues about their composition. Located about 40 light-years away, TRAPPIST-1 is home to the largest group of roughly Earth-size planets ever found in a single stellar system. Previous calculations determined that the planets are roughly the size and mass of Earth and thus must also be rocky, or terrestrial -- as opposed to gas-dominated, like Jupiter and Saturn.