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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.


Pluto February 19, 2016

Radio Programs

Moon and Pluto Lining up with Pluto November 12, 2018

Plutonian Names New names for a distant world November 3, 2017

Kuiper Belt Discovering the Kuiper Belt August 30, 2017

Looking for Life Looking for life in a cold ocean March 28, 2017

Red Ice A “beanie cap” for Pluto’s big moon December 27, 2016

Icy Pluto Pluto’s icy “heart” December 26, 2016

One Year Later, II Creation from cosmic violence July 19, 2016

One Year Later One year after Pluto July 18, 2016

Plutonium A new element for a new world — after this. February 24, 2016

New Pluto A new view of a distant world December 22, 2015

New Horizons II Getting to know a new world July 9, 2015

New Horizons Transforming a distant world July 8, 2015

Pluto’s Moons A small world with a big moon July 7, 2015

Pluto A famous but poorly understood world July 6, 2015

Kuiper Belt “Little guys” at the edge of the solar system July 5, 2015

First Glimpse Ready for a first look at Pluto January 8, 2015

Moon and Jupiter Closing in on two dwarf planets January 6, 2015

Eris Reflections on a bright dwarf planet January 5, 2015

Dwarf Planets A new name for leftover building blocks January 4, 2015

Featured Images

Enhanced-color image of Charon from New Horizons

Charonian Chapeau December 27, 2016

View of ice field on Pluto from New Horizons

Plutonian Lava Lamp July 18, 2016

Backlit view of Pluto landscape from New Horizons

Hazy Skies September 22, 2015

New Horizons view of young mountains on Pluto

Ice Mountains July 15, 2015

July 12 views of Charon and Pluto from New Horizons

Hours Away July 13, 2015

July 8 view of Charon, Pluto from New Horizons

Dynamic Duo July 10, 2015

Artist's concept of New Horizons passing by Pluto

First Encounter July 9, 2015

New Horizons view of Pluto and Charon, July 1, 2015

Best Shot July 7, 2015

Diagram shows the location of the Kuiper Belt

Icy Realm July 6, 2015

Three dwarf planets shown to scale with Earth and Moon

Dwarf Planets January 5, 2015