GJ 9827 is an orange K-type dwarf (about 0.62 solar masses, 4,236 K, 0.58 solar radii), 29.7 light-years from Earth. GJ 9827's three planets straddle the radius valley, with rocky and gaseous worlds orbiting the same star. GJ 9827 b is a 4.3-Earth-mass planet, with an orbital period of 1.2 days, at 0.019 AU from its star, and an equilibrium temperature near 1,035 K, discovered in 2017 via transit. GJ 9827 c is a 1.9-Earth-mass planet, with an orbital period of 3.6 days, at 0.040 AU from its star, and an equilibrium temperature near 716 K, discovered in 2017 via transit. Mutual gravitational tugs between the planets can slowly reshape their orbits, preserving clues to the system's assembly.