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...

Featured Images

Backlit view of Pluto landscape from New Horizons
Hazy Skies Tuesday, September 22, 2015
New Horizons view of young mountains on Pluto
Ice Mountains Wednesday, July 15, 2015
July 12 views of Charon and Pluto from New Horizons
Hours Away Monday, July 13, 2015
July 8 view of Charon, Pluto from New Horizons
Dynamic Duo Friday, July 10, 2015
Artist's concept of New Horizons passing by Pluto
First Encounter Thursday, July 9, 2015
New Horizons view of Pluto and Charon, July 1, 2015
Best Shot Tuesday, July 7, 2015
Diagram shows the location of the Kuiper Belt
Icy Realm Monday, July 6, 2015
Three dwarf planets shown to scale with Earth and Moon
Dwarf Planets Monday, January 5, 2015

Radio Programs

New Horizons II Getting to know a new world Friday, July 10, 2015
New Horizons Transforming a distant world Thursday, July 9, 2015
Pluto’s Moons A small world with a big moon Wednesday, July 8, 2015
Pluto A famous but poorly understood world Tuesday, July 7, 2015
Kuiper Belt “Little guys” at the edge of the solar system Monday, July 6, 2015
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


©2015 The University of Texas McDonald Observatory