The prototype "dwarf planet," Pluto orbits the Sun at an average distance of 39.5 times the distance between Earth and Sun. Pluto has a mass 0.002 times the mass of Earth and a radius 0.18 times the radius of Earth. It is a small body made of water ice, and temperatures there do not rise above minus-223 degrees Centigrade. Pluto has five known moons. Discovered in 1930, it originally was classified as a planet, but was demoted in 2006.


Remnants from the Beginning Whenever you build a new house, you always have...
Pluto After 76 years of glory, the small ball of rock...

Radio Programs

First Glimpse Ready for a first look at Pluto Friday, January 9, 2015
Moon and Jupiter Closing in on two dwarf planets Wednesday, January 7, 2015
Eris Reflections on a bright dwarf planet Tuesday, January 6, 2015
Dwarf Planets A new name for leftover building blocks Monday, January 5, 2015
Orcus Giving birth to a distant moon Thursday, December 9, 2010
Eris Sowing discord in the outer solar system Wednesday, December 8, 2010
Distant Iceballs Clearing up some distant definitions Tuesday, December 7, 2010

Featured Images

Three dwarf planets shown to scale with Earth and Moon
Dwarf Planets Monday, January 5, 2015


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