Should Pluto be a planet? Does it matter? One group of NASA scientists are emphatic. Yes on both. One month after a group of NASA scientists proposed a new definition for what makes a planet, the idea is gaining steam again. This time around it’s Johns Hopkins University scientist Kirby Runyon.

Here’s a little backstory for those who don’t understand what’s going on. Back in 2006, the International Astronomical Union approved a definition for what makes a planet. Basically, a planet needs to be round, orbit the sun and clear all the space junk around its orbit. That definition nixed Pluto from the planetary lineup. The problem seems to stem from the fact Pluto crosses Neptune’s orbit for a short time during its long trip around the sun.

Runyon argues Pluto “has everything going on on its surface that you associate with a planet. There’s nothing non-planet about it.” I’ll give Runyon that. New Horizons showed us Pluto isn’t the drab world towards the end of the solar system we all believed it to be. Blue hazes, red ice, stunning plains and icy mountains dot the small planet’s surface.

Pluto red ice

Ok, so what makes a planet according to Runyon and his colleagues? For them, it’s about the body itself. Not the orbit. As long as it’s a sub-stellar body that hasn’t undergone nuclear fusion and looks roughly like a sphere it should be a planet. There’s no mention of orbit clearing in the proposed definition.

I should note that Runyon and his colleagues are all team members of the New Horizons mission to Pluto. In case you’re wondering why they are pushing so hard for this new definition.

While it looks like this is all about Pluto, it’s actually about much more. The new definition wouldn’t increase our planet back to nine. It would multiply it many times to 110. With orbit characteristics tossed out the window, any round body that’s not a star gets added. That means round moons around planets and small round bodies in the asteroid belt. Ceres, Europa, Titan, the Moon. All would be considered planets under this definition.

Plus, the new definition could help NASA do more of their important work. Runyon believes the word planet carries a “psychological weight.” He believes adding the planet moniker to more worlds could boost public interest.

It could also dilute it. Going from eight to 110 planets seems a bit extreme. Less is more. How about throw out moons and leave the rest. That would add Ceres, Pluto, Eris and perhaps a few more Kuiper Belt objects.

But hey, if calling them planets gets more public interest for NASA, and in turn, more funding I say go for it. New Horizons shows the kind of interest a successful mission to a mysterious world can generate. If calling Europa a planet gets the lander mission approved, then call it a planet.

“I want the public to fall in love with planetary exploration as I have,” says Runyon. “It drives home the point of continued exploration.”

We all fell in love with Pluto since New Horizons revealed the icy world on July 14, 2015.

Runyon is going to be at the Lunar and Planetary Science Conference today and will be on hand to answer questions about the new planet definition.



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