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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

Wispy Skies The wispy blue skies of Pluto July 25, 2023

Bright Heart Pluto’s bright, cold heart July 24, 2023

Vanishing Air Pluto’s air gets ready to “hibernate” January 20, 2022

Pluto at Opposition A little world gets pushed around July 15, 2021

Deep Ocean A deep and ancient ocean on Pluto July 14, 2021

Building a World Assembling a small planet July 13, 2021

Beyond Neptune Denizens of the deep solar system May 26, 2021

Changing Skies? Pluto may be losing its atmosphere February 3, 2021

Getting Moons Many ways to acquire moons September 23, 2020

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

Featured Images

Falling Skies January 20, 2022

Building Worlds July 13, 2021

New Horizons view of haze in Pluto's atmosphere

Changing Skies? February 3, 2021

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