Pluto

Pluto

Pluto is a dwarf planet in the Kuiper Belt region of the Solar System. It is the second-largest known dwarf planet next to Eris, and was considered a full-fledged planet until 2006.

Fast Facts

Discovered by Clyde Tombaugh
Discovered on: February 18, 1930
Was considered a planet for 76 years
Downgraded to a dwarf planet on August 24, 2006
Named after the Roman god of the underworld
Radius: 1,151 kilometers (18% of Earth's)
Circumference: 7,232 kilometers
Surface area: 16.65 million square kilometers (3% of Earth's)
Mass: 1.3x10²² kilograms
Average distance from the Sun: 5.91 billion kilometers
Three known moons in its orbit¹
Atmospheric Composition (percentages unknown):
1. Methane
2. Nitrogen²
Tenth-largest known entity that orbits the Sun

Demotion

In 2006, the International Astronomical Union altered the standards for what makes an object a planet. It established three criteria that the object must meet:

Must orbit the Sun
Must generate significant enough gravity to force a roughly spherical shape
Must have cleared other objects out of its immediate area in space

Pluto did not satisfy the third criterion, and was thus downgraded to a dwarf planet.³

Categories

Science | Astronomy | Planets

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The Mahalo Top 7

Wikipedia: Pluto
NASA: Solar System Exploration: Pluto
NASA: NSSDC Lunar and Planetary Science: Pluto
Encyclopaedia Britannica: Pluto
The Planetary Society: Space Topics: Pluto and Charon
Solar Views: Pluto
Nine Planets: Pluto

Pluto News and Articles

ScienceDaily
Universe Today: Pluto News
Pluto Today: News About Pluto, Charon, and other Kuiper Belt Objects
Space.com: Pluto: From Planet to Dwarf Planet
Johns Hopkins University's APL: New Horizons Mission News Center

Pluto History and Background

Brad Mager: Pluto: The Discovery of Planet X
BBC: The Girl Who Named a Planet (2006)
NASA: Pluto Classification and Exploration (2006)
Neil deGrasse Tyson: Pluto's Honor (1999)

Pluto Educational Resources

NASA: Space Science Education Resource Directory: Pluto
NASA: Space Place: Pluto, King of the Ice Dwarfs
New Horizons: What We Know About Pluto, Charon and the Kuiper Belt
New Horizons: Educators Guide
Astronomy Education Review: Teaching What a Planet Is

Pluto Photos and Videos

JPL's Planetary Photojournal: Catalog Page: Pluto
Johns Hopkins University's APL: New Horizons Image Gallery
Windows to the Universe: Pluto Image Archive
YouTube & Google Video: Pluto

Pluto Blogs and Forums

LiveScience.com Blogs: Polite Demotion Planned for Planet Pluto (2006)
The Planetary Society Weblog: Pebbles and Pluto (2006)
Bad Astronomy Blog: Breaking News - Pluto Not a Planet!
Scientific American Blogs: Farewell, Pluto (2006)
Wired Science: When I was Your Age Pluto Was a Planet (2007)

Pluto Organizations and Societies

iPetitions.com: Petition Protesting the IAU Planet Definition
Please Save Planet Pluto: A Petition To Help Pluto Regain Its Status as a Planet
Save Pluto: Petition to Set Aside the Current Pluto Definition

Pluto Fun Stuff

The Brunching Shuttlecocks: Another Brief Conversation with the Planet Pluto
Kloonigames: Pluto Strikes Back
The Onion: NASA Launches Probe To Inform Pluto Of Demotion
Yahoo! Video: Pluto Press Conference
Photograph: Poor Pluto

Pluto Books

Amazon.com: Clyde Tombaugh: Discoverer of Planet Pluto by David H. Levy
Amazon.com: Out of the Darkness: The Planet Pluto by Clyde W. Tombaugh
Amazon.com: Pluto and Beyond: A Story of Discovery, Adversity, and Ongoing Exploration by A. Minard
Amazon.com: Pluto and Charon: Ice Worlds on the Ragged Edge of the Solar System by Alan Stern
Amazon.com: Is Pluto a Planet?: A Historical Journey through the Solar System by David A. Weintraub
Amazon.com: The Pluto Files: The Rise and Fall of America's Favorite Planet by Neil deGrasse Tyson

Related Pages on Mahalo

Astronomy | Solar System | Dwarf Planet | Charon | Nix | Hydra | Eris | Ceres | New Horizons

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