NASA's visit to Pluto has scientists debating the definition of a planet again

A surprising amount of people were outraged when a gang of astronomers “demoted” Pluto from a planet to a dwarf planet in 2006.

Passionate Earthlings launched protests and petitions. Popular scientists like astrophysicist Neil deGrasse Tyson told us to get over it. And after the New Horizons historic flyby of Pluto, Tyson still hasn’t changed his mind:

Stephen Colbert even tried to change Tyson’s mind with ice cream and Tang, to no effect:

But NASA’s New Horizons principle investigator Alan Stern, a planetary scientist at the Southwest Research Institute in Colorado, is pretty adamant that Pluto should be classified as a planet.

Stern thinks the data coming in from the New Horizons spacecraft’s Pluto flyby will change the way we view this tiny world. Here’s the full comment that he gave TED about Pluto’s planetary status:

It’s a planet. Science doesn’t work by voting. Did people vote on the theory of relativity? No! It’s either right or it’s wrong. Do we vote on whether genetics is a good theory or not? Of course not. Either data supports the observations or they don’t. Voting doesn’t work in science.

Pluto is as far across as Manhattan to Miami, but its atmosphere is bigger than the Earth’s. It has 5 moons, it has atmosphere, weather. If it walks like a duck, it’s a duck. We’re showing the world this beautiful planet. And it’s a double planet, which is even more awesome.

Of course Stern has dedicated the last 26 years to a Pluto mission. So obviously this is a big moment for him. There was lots of fist-pumping and hugging from the guy when the New Horizons team confirmed that the spacecraft survived its Pluto flyby and had all its data intact:

Stern isn’t the only person (or scientist, for that matter) who thinks Pluto deserves planet status.

During a press conference, after the New Horizons team confirmed that the spacecraft had the Pluto flyby, Charles Bolden —  NASA’s chief administrator — said he hoped that Pluto’s classification would change.

“I call it a planet, but I’m not the rule maker,” Bolden said.

Business Insider asked a few other astronomers to weigh in on whether they think this new data from New Horizons has the potential to change Pluto’s planetary status.

Victor Baker, a professor of planetary sciences and geosciences at the University of Arizona, said the latest images can’t tell us much about whether Pluto should or shouldn’t be a planet.

“The classification of Pluto as a dwarf planet is really not based on criteria affected by the new images,” Baker told Business Insider in an email. “The issue is that there are other planetary objects in the far outer system that are very similar to Pluto in size and general character.”

He pointed to dwarf planet Ceres as a good example of this. The issue becomes if we start naming things like Ceres and Pluto as planets, there could be dozens and dozens of bodies that fit into the category.

Others think the question is a little more complicated than just “planet or not a planet.”

“I think that [data from the New Horizons mission] will have an effect, but I think eventually we have to change the definition of ‘planet,'” Phil Metzger, a planetary physicist who recently retired from NASA’s Kennedy Space Center, told Business Insider. “And that definition will end up including Pluto.”

Metzger said the problem is our current definition of “planet” doesn’t work when we start to compare our Solar System to others ones light-years away from the Sun. Basically, he argues the real problem lies in the parameters we use to classify planets in the first place.

“When we try to do that planets similar to Earth would not be called ‘planets,’ and really small rocky bodies would be called ‘planets,'” Metzger said.

Tyson takes a different view. He recently told Colbert that small, rocky planets like Pluto and Earth should all be classified as “dwarf planets,” since they’re so small relative to gassy giants like Neptune, Uranus, Saturn, and Jupiter.

But astronomer Mike Brown, who goes by the handle “@plutokiller” on Twitter (for his direct role in the planet’s demotion), made a really great point that should satisfy all the pro-planet status folks:


NOW WATCH: Bill Nye and NASA scientists react to seeing a clear picture of Pluto for the first time

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