Moons of Pluto while searching for Plutonian rings. Styx, announced on 7 July 2012, was discovered while looking for potential hazards for "New Horizons". Charon is about half the diameter of Pluto and is so massive (nearly one eighth of the mass of Pluto) that the system's barycenter lies between them, approximately 960 km above Pluto's surface. Charon and Pluto are also tidally locked, so that they always present the same face toward each other. The IAU General Assembly in August 2006 considered a proposal that Pluto and Charon be reclassified as a double planet, but the proposal was abandoned. Pluto's four small
Makemake Makemake Makemake (minor-planet designation 136472 Makemake) is a dwarf planet and perhaps the largest Kuiper belt object in the classical population, with a diameter approximately two-thirds that of Pluto. Makemake has one known satellite, S/2015 (136472) 1. Makemake's extremely low average temperature, about , means its surface is covered with methane, ethane, and possibly nitrogen ices. Makemake was discovered on March 31, 2005, by a team led by Michael E. Brown, and announced on July 29, 2005. Initially, it was known as and later given the minor-planet number 136472. Makemake was recognized as a dwarf planet by the International Astronomical