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Space Topics

Pluto Top Ten


To celebrate the New Horizons mission and to draw attention to an interesting scientific debate, The Planetary Society issued a worldwide call for the Top 10 Reasons Pluto is -- and is not -- a planet.

The Results Are In!


The Top Ten Reasons Why Pluto Is a Planet

10. Possession is nine tenths of the law.
Don C, Santa Cruz, CA
9. Look what happened after 40 years of arguing about the name of Planet 7 - we got Uranus.
George C, San Antonio, TX
8. [Pluto is] god of the Underworld, not god of the Underachieving World.
Earl G, Radford, VA
7. The solar system will be too sexual if it is no longer "plutonic."
Paul K, Gilroy, CA
6. It would annoy Neil Tyson no end NOT to reclassify Pluto, and that makes for good entertainment for the astronomical community.
Lonny B, Parsippany, NJ
5. We'd have to rename Plutonium if it wasn't. Transneptunianium? Yuck.
Lyford R, Ventura, CA
4. If Pluto isn't a planet, then My Very Eager Mother Just Sewed Us New...What? New what!
Doug E, Leicester, UK
3. It annoys people who like tidy categories.
Dennis D, Baton Rouge, LA
2. I'd like a few of the things that I learned in grade school still to be true.
David S, Kingwood, TX
1. Eight Is NOT Enough.
Jim B, Pasadena, CA

The Top Ten Reasons Why Pluto Is Not a Planet

10. If 7-8-9 then only 8 planets remain.
Greg M, Costa Mesa, CA
9. Pluto fans didn't raise enough money to bribe the members of the IAU (International Astronomical Union).
Torsten Z, Germany
8. When my son asks "Why is Pluto a planet, but Ceres isn't?" I want a better answer than "Old people are afraid of change."
Joshua B, Seattle, WA
7. Things are tough all over. It's time to tighten our Kuiper belt and kick out the stragglers.
Alan C, San Antonio, TX
6. It would be the first planet to melt into a puddle of water and pebbles if it got too warm.
Jane, Silver Springs, MD
5. We could retroactively say that Voyager 2 DID complete the Grand Tour of Outer Planets.
Lyford R, Ventura, CA
4. As a small body in the outer solar system, Pluto is lowering the property values of its larger neighbors.
Dave O, Fenton, MI
3. Pluto is a Disney character who has been in 48 of his own cartoons, which makes him a star, not a planet.
Ryan C, North Adams, MA
2. I would finally be able to listen to Holst's "The Planets" without feeling shortchanged.
Lyford R, Ventura, CA
1. It doesn't appear to be so inclined.
Lyford R, Ventura, CA

Pluto, named for one of the mythological gods of the underworld, is the last of the nine planets to be explored -- or is it? Some scientists claim that Pluto does not deserve its planetary ranking, that it is instead a Kuiper belt object, one of many such bodies in the far reaches of the solar system.

While The Planetary Society can't determine Pluto's status, we can expand the discussion about it. In honor of the launch of the New Horizons mission to Pluto, we launched The Planetary Society's Search for the Pluto Top Ten Lists!

Read more about Pluto's status as a planet in essays by The Planetary Society's Chairman of the Board, Neil deGrasse Tyson, and the Society's Vice-President Bill Nye. Whether you consider Pluto the last planet, the first Kuiper Belt Object, or something else entirely, the New Horizons mission will powerfully expand our scientific knowledge and the exploration of our solar system.