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
Tombaugh Regio the International Astronomical Union (IAU), together with names for 13 other surface features on Pluto. Some people find the feature also resembles the Disney character Pluto, an animated non-anthropomorphic dog which shares the name of the dwarf planet. The Walt Disney Company acknowledged this perceived likeness in a short animation. Tombaugh Regio Tombaugh Regio (), nicknamed The Heart after its shape, is the largest bright surface feature of the dwarf planet Pluto. It is just north of the equator, to the northeast of Cthulhu Macula and to the northwest of Krun Macula, which are both dark features. Its western lobe,