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Recent news seem to suggest that astronomers are arguing about whether Pluto should become a planet again.

However, I cannot find an official source for this. Is this actually true?

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    $\begingroup$ There is only one way to end this conflict once and for all... destroy Pluto $\endgroup$ – toniedzwiedz Oct 5 '14 at 15:13
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    $\begingroup$ @Tom I doubt the New Horizons probe has an explosive device on board. :-) $\endgroup$ – HDE 226868 Oct 5 '14 at 15:15
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    $\begingroup$ @HDE226868 I'm starting to wonder how much money I could gather on kickstarter to launch a device that could handle the job. Would a cost estimate be a legitimate question on this site? $\endgroup$ – toniedzwiedz Oct 5 '14 at 15:16
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    $\begingroup$ @Omen I just emailed what-if, I hope this will be answered. $\endgroup$ – toniedzwiedz Oct 5 '14 at 15:29
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    $\begingroup$ @Tom, alas, if we destroy Pluto, academics will start arguing about what Pluto was. $\endgroup$ – msw Oct 6 '14 at 1:01
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Yes, Pluto is still a dwarf planet. According to the IAU website, it still fits the criteria for a dwarf planet, fails to meet the criteria for a planet, and still carries the "dwarf planet" label, whatever its future status may be. I'm sorry I can't provide a longer or more detailed answer, but this is really a yes-or-no question.

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  • $\begingroup$ Good answer, the media certainly plays on any little deviation, as they did with the debate quoted in my answer. $\endgroup$ – user2449 Oct 5 '14 at 15:26
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    $\begingroup$ @Omen Thanks. My answer is boring, but I couldn't find much else. I decided to avoid Wikipedia for this one. $\endgroup$ – HDE 226868 Oct 5 '14 at 15:28
  • $\begingroup$ It was just by chance I was reading about the debate in my answer when the question appeared - the rest of the reports are just the media. $\endgroup$ – user2449 Oct 5 '14 at 15:30
  • $\begingroup$ Your answer is doing better than mine..;) $\endgroup$ – user2449 Oct 5 '14 at 15:40
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    $\begingroup$ @Omen We'll see. Low views for the question so far. . . But good upvotes for the question itself. $\endgroup$ – HDE 226868 Oct 5 '14 at 15:41
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A lot of the push to have Pluto reinstated as the 9th planet is coming from Harvard, from their press release Is Pluto a Planet? The Votes Are In (Released September, 2014), they state the following outcomes from a debate:

Science historian Dr. Owen Gingerich, who chaired the IAU planet definition committee, presented the historical viewpoint. Dr. Gareth Williams, associate director of the Minor Planet Center, presented the IAU's viewpoint. And Dr. Dimitar Sasselov, director of the Harvard Origins of Life Initiative, presented the exoplanet scientist's viewpoint.

Gingerich argued that "a planet is a culturally defined word that changes over time," and that Pluto is a planet. Williams defended the IAU definition, which declares that Pluto is not a planet. And Sasselov defined a planet as "the smallest spherical lump of matter that formed around stars or stellar remnants," which means Pluto is a planet.

We will have a better understanding of Pluto, hence its classification when NASA's Horizons mission reaches it. But, at this stage, Pluto is still classified as a dwarf planet.

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    $\begingroup$ It would have been awesome to be at this debate $\endgroup$ – user2449 Oct 5 '14 at 15:23
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    $\begingroup$ For a second, I saw "Gingrich" instead of "Gingerich" and got really worried. $\endgroup$ – HDE 226868 Oct 5 '14 at 15:24
  • $\begingroup$ You and me both! $\endgroup$ – user2449 Oct 5 '14 at 15:24
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    $\begingroup$ "(T)he smallest spherical lump of matter that formed around stars or stellar remnants" would raise the number to higher than nine for our solar system. Pluto could then be the 10th planet since Ceres was called a planet more than a century before Pluto, and Ceres still fits the quoted definition. At least Eris, Makemake and Haumea would also need to be added, giving us 13 "planets" so far, with more likely to be found. (It's less clear about Charon.) We're getting crowded. $\endgroup$ – user2338816 Oct 6 '14 at 5:23
  • $\begingroup$ @user2338816 I agree that Charon doesn't even fit the dwarf planet definition, partly because it doesn't hold gravitational dominance over its surroundings. $\endgroup$ – HDE 226868 Oct 7 '14 at 1:41
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Pluto will continue to be exactly Pluto no matter how we choose to categorize it. Fretting about the "proper" category is the tyranny of the discontinuous mind.

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    $\begingroup$ In that case, we're all tyrants. Richard Dawkins can be an atheist's best friend, but at the moment he's irrelevant. It's a deep answer, though. Philosophical. $\endgroup$ – HDE 226868 Oct 6 '14 at 1:07
  • $\begingroup$ I cited Dawkins because I know I cribbed the phrase from somewhere (Dennet, Hofstadter, maybe?) but didn't look real hard for the source. The Dawkins article was more political than I wanted, but it did cover the concept well. And yes, we are all categorizing "tyrants" except those who have stars on our bellies; even Dr. Seuss gets philosophical at at times. $\endgroup$ – msw Oct 6 '14 at 1:15
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Yes, Pluto is a dwarf planet, along with Ceres and Eris which are in the Solar System. It was classified a dwarf planet in 2006 or 2007. Sorry for my inaccurate answer.

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  • $\begingroup$ No, it's accurate. $\endgroup$ – HDE 226868 Jan 18 '15 at 1:17
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Currently, Pluto is very much a dwarf planet. I don't think Pluto will ever be reinstated as a planet again . . . On the the pro-planet side, Pluto has five moons, which can possibly qualify it as a planet. On the no-planet side, Pluto has a mass of 1.30900 × 10^22 kilograms, which is much lower than the currently smallest planet, Mercury, which weighs 328.5 x 10^21 kilograms. Also, the diameter of Mercury is 4,879.4 km across, while Pluto’s diameter is 2,360 km across. Big difference. Really. I'm pretty sure Pluto won't be called a planet again, but I can't be certain. Look, here's the thing about controversies like this: you never know until they're over. Yes, it's a horrible answer, but it's the candid truth. At least I've given you the data.

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The 3rd requirement for a celestial object to be a planet is that it has to "clear its neighborhood" which means it has to be gravitationally dominant. Pluto has not enough mass to interact with other object in its orbit(consuming them or swinging them away) and it is only 0.07 times the mass of the other objects in its orbit. Earth is 1.7 million times the mass of other objects in its orbit.

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