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Speaking of Science

Nah, this possible new ninth planet isn't Pluto

By Elahe Izadi

January 20, 2016 at 1:45 PM

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Astronomers say they have evidence of a ninth planet in our solar system. Here's what they say they know about it. (Joel Achenbach, Gillian Brockell/The Washington Post)

Scientists announced some breaking universe news on Wednesday: Evidence suggests a ninth planet has been lurking in our solar system. They're calling it "Planet Nine."

Is Planet Nine Pluto? Nah. This new "planetis not Pluto. Here's why:

Planet Nine > Pluto

We're talking size, people. Planet Nine is massive. Pluto, comparatively, isn't. Astronomers at the California Institute of Technology believe Planet Nine is five to 10 times as massive as Earth, and astronomer Mike Brown told The Post "it's 5,000 times the mass of Pluto."

We have seen Pluto. We have not seen Planet Nine.

Pluto has been discovered (sorry, truthers). We have photographic evidence of Pluto's existence. Here it is:

Image of Pluto captured by NASA’s New Horizons spacecraft on July 13, 2015, when the spacecraft was 476,000 miles from the surface. (EPA/NASA)

Planet Nine actually hasn't been discovered. It hasn't been seen through a telescope. At this point, Planet Nine's existence is theoretical, in part based upon how dwarf planets and other small objects in the neighborhood move. It seems like there's a "massive perturber" lurking about, and the gravity of this potential new planet could be influencing the orbits of nearby bodies.

Now, here's a helpful diagram that clearly demonstrates how Pluto is not Planet Nine:

Image to the left shows Pluto (NASA). Image to the right shows ¯\_(ツ)_/¯. (Elahe Izadi)

There's a lot of stuff in the outer solar system that isn't Pluto

Space may seem empty and vast and whatnot, but astronomers previously discovered more than 30 dwarf planets and other objects in the outer reaches of our solar system. One such dwarf planet, Eris, is actually bigger than Pluto. Eris ≠ Pluto, Eris ≠ Planet Nine, Planet Nine ≠ Pluto, etc. (Also, see above for the equation "Planet Nine > Pluto.")

Being salty about Pluto getting the boot does not make "Planet Nine" Pluto.

Look, I get it: You're still upset about Pluto's demotion from the solar system, the makeup of which you committed to memory as a child. Just think about how Pluto must feel. But it's time to let it go.

A decade ago, when the International Astronomical Union defined what constitutes a planet, Pluto and Eris got the boot and were classified as dwarf planets. That same set of criteria would be used to usher in "Planet Nine" into our solar system. If/when it is discovered, researchers say, it will fit the planet criteria.

So, here's the bright side for nine-planet solar system proponents: You may get your ninth planet after all!

Which, by the way, will not be called "Planet Nine." That's right, Planet Nine will not be (named) Planet Nine. It won't be Pluto, either — you can't have a dwarf planet and a planet planet with the same name. You're just going to have to memorize a new one.

READ MORE:

New evidence suggests a ninth planet lurking at the edge of the solar system

Q&A: The 'Pluto Killer' who thinks he's found the true ninth planet

Pluto is a bit bigger than we'd thought


Elahe Izadi is a pop culture writer for The Washington Post.

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