Astronomers using the Hubble Space Telescope discovered a moon orbiting dwarf planet Makemake -- the third largest known object past the orbit of Neptune, about two thirds the size of Pluto. Further observations of this moon may allow astronomers to calculate Makemake's mass, which will give them a better idea of its density and thus its bulk composition. The Hubble Space Telescope has been instrumental in studying our outer solar system; it also discovered four of the five moons orbiting Pluto.