Scientists on Wednesday (July 11) announced the discovery of a fifth moon orbiting Pluto in a major solar system find. But while many people think of moons as accessories for planets, like the Earth's moon or Jupiter's many moons, Pluto doesn't quite make the cut in the International Astronomical Union's (IAU) definition of "planet."
This image, taken by NASA's Hubble Space Telescope, shows five moons orbiting the distant, icy dwarf planet Pluto. The green circle marks the newly discovered moon, designated P5, as photographed by Hubble's Wide Field Camera 3 on July 7, 2012.
CREDIT: NASA, ESA, and M. Showalter (SETI Institute)
Despite of some determined lobbying by die-hard supporters to change its dwarf planet status,more moons around Pluto won't change its classification, experts say.
The IAU ruled that to be called a planet, an object has to meet three conditions. It must orbit the sun without being another object's satellite, it must have enough gravity to make it sphere-shaped and it must clear the area around it of other objects. But even with Pluto's five moons, it doesn't "clear the neighborhood."
No one has found any other dwarf planet that has five moons, but that may be because scientists have studied Pluto more carefully than other dwarf planets