Celebrate Pluto Demoted Day Every August 24

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Did you grow up believing Pluto was a planet? I mean a real planet, not this “dwarf planet” status it’s saddled with now. Were you outraged at poor little Pluto’s demotion?

If so, prepare to revive your outrage. August 24 is Pluto Demoted Day—the anniversary of the 2006 day when astronomers demoted Pluto to a dwarf planet.

Dwarf! Isn’t that offensive? Derogatory? Suggesting that Pluto just doesn’t measure up?

Humph!

And you know what the silliest part is? They made this decision just a few months after launching New Horizons. You know, the spacecraft that flew by Pluto in July 2015.

Seems like a lot of effort for a bit of space rock! … No, no. We don’t believe Pluto’s just a big rock. But that was what the demotion seemed like.

To be fair though, in 2011 Alan Stern, the lead scientist of the New Horizons mission, said he believes Pluto is a planet.

We don’t know who first decided to mark the anniversary of Pluto’s demotion. We’re guessing it was someone who wasn’t happy about it.

 

A Bit of Pluto History

Pluto orbited the sun unknown and unloved until February 18, 1930. That’s when Clyde Tombaugh, at the Lowell Observatory in Flagstaff, Arizona, discovered the littlest planet in our solar system.

(A quick side note for Illinoisans who may not be overly proud of their state these days: Clyde Tombaugh was born and raised in Streator, IL. That’s where he cultivated his interest in astronomy, peering at the heavens through his uncle’s telescope.).

In fact, it’s even smaller than the Moon. But no matter. This tiny orb got a powerful name when the Lowell Observatory accepted suggestions for its name. An 11 year old girl from England, Venetia Burney, suggested naming it for the ancient Greek ruler of the underworld. The name became official on March 24, 1930.

We don’t know too much about Pluto, given how far it is from us. That’s a big part of the reason for the New Horizon mission. A few things we do know:

• It has a very long orbit around the sun. One Pluto year is equal to 249 Earth years. Yikes!
• One day on Pluto (one full rotation on its axis) takes bout 6.5 Earth days.
• It has five moons: Charon, Kerberos, Nix, Hydra and Styx.

 

Pluto reigned as the 9th planet for 76 years, until that fateful vote by the International Astronomical Union (IAU) in 2006.

Why did the IAU create Pluto Demoted Day (not intentionally of course … the day’s a side effect of the Union’s vote)? Because it only meets two of the three criteria used to define a planet. It does:

• Orbit around the sun
• Have enough mass to give it a nearly round shape

 

But it has not “cleared the neighborhood around its orbit” of other objects.

What does that mean? It means that the planet shares its space with other objects of comparable size, but without drawing them into its orbit (putting them under its gravitational influence, like a moon).

It fails that test because there are other objects similar in size and even bigger than Pluto in the Kuiper Belt (essentially Pluto’s neighborhood).

Well boo-hoo. That’s a silly requirement for calling something a planet!

And apparently many planetary scientists agree. And to be clear, planetary scientists are not the same as astronomers … It was astronomers who demoted Pluto. (Bad astronomers!).

Scroll down for some ideas on celebrating this unofficial space holiday.

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Ideas For Celebrating Pluto Demoted Day

Spend the day learning a bit more about space, our solar system and what makes a planet a planet.

You might like to start with a bit more history of Pluto itself.

You might also like one of these books about Pluto:

• The Pluto Files: The Rise and Fall of America’s Favorite Planet, by Neil deGrasse Tyson
• Pluto: New Horizons for a Lost Horizon: Astronomy, Astrology, and Mythology, by Richard Grossinger

 

Learn more about dwarf planets, since that’s what Pluto is now called. Check out these pages:

• Dwarf Planet Facts
• What Is A Dwarf Planet?
• The Dwarf Planets

 

And the self-described “man who killed Pluto” has also written a book you might find interesting: How I Killed Pluto and Why It Had It Coming.

Your kids might be interested in this Dwarf Planet Facts page from Science Kids. Or the book Pluto’s Secret: An Icy World’s Tale of Discovery, by Margaret Weitekamp (suggested for ages 6-9).

View images from the New Horizons mission.

If you live near a planetarium, today’s the perfect excuse for a visit. Especially if you have kids (but don’t let not having kids stop you!).

Find the planetarium nearest you here. Even if you don’t think there’s one nearby, you might be surprised. Turns out I only knew about 2 of the 7 planetariums in Illinois. And 2 of the ones I’d never heard of aren’t too far away!

So, how will you be spending Pluto Demoted Day?

 

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