# Revived question: Is Pluto a planet?
**URL:** https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953
**Category:** Factual Questions
**Created:** [August 14, 2008, 6:42am UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953 "2008-08-14T06:42:24Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@dougie\_monty](https://boards.straightdope.com/u/dougie_monty)
#### Post date: [August 14, 2008, 6:42am UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/1 "2008-08-14T06:42:24Z")
On the “welcome” dialog box for AOL, one of the news items shown is a squib about some astronomers making an effort to have the designation of Pluto as a “dwarf planet,” by the International Astronomical Union, rescinded so Pluto will be the ninth planet again. One of the links was to a website with a rather sentimental message board saying things like “Save Pluto.”
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### Author:  [@Full\_Metal\_Lotus](https://boards.straightdope.com/u/Full_Metal_Lotus)
#### Post date: [August 14, 2008, 7:12am UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/2 "2008-08-14T07:12:02Z")
Pluto should probably be considered a planet.
Its the same thing as Europe being considered a continent. Its on the “maps” as such, and has a historical record.
By Modern standards, not really…
but let’s “grandfather” it in…
FML
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### Author:  [@kellner](https://boards.straightdope.com/u/kellner)
#### Post date: [August 14, 2008, 7:36am UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/3 "2008-08-14T07:36:05Z")
[QUOTE=Full Metal Lotus]
Its on the “maps” as such, and has a historical record.
[/QUOTE]
But only for a few decades, not unlike Ceres. It just happens to be the time when most people who are around now went to elemetary school.
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### Author:  [@Derleth](https://boards.straightdope.com/u/Derleth)
#### Post date: [August 14, 2008, 9:08am UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/4 "2008-08-14T09:08:21Z")
Let’s let astronomy be a science _not_ ruled by popular whim, shall we? Pluto isn’t a planet due to a reasonable and self-consistent definition of the term, not due to arbitrary decree and certainly not because anyone wants to make anyone else angry. Must everything degenerate into a popularity contest?
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### Author:  [@pseudotriton\_ruber\_ruber](https://boards.straightdope.com/u/pseudotriton_ruber_ruber)
#### Post date: [August 14, 2008, 9:45am UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/5 "2008-08-14T09:45:01Z")
[QUOTE=Derleth]
Must everything degenerate into a popularity contest?
[/QUOTE]
How many of you think everything should degenerate into a popularity contest?
Come on, let’s get those hands in the air. You, there! No, the person sitting by the monitor–yes, you. Raise that hand!
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### Author:  [@Marley23](https://boards.straightdope.com/u/Marley23)
#### Post date: [August 14, 2008, 12:39pm UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/6 "2008-08-14T12:39:44Z")
[QUOTE=Derleth]
Let’s let astronomy be a science _not_ ruled by popular whim, shall we? Pluto isn’t a planet due to a reasonable and self-consistent definition of the term, not due to arbitrary decree and certainly not because anyone wants to make anyone else angry.
[/QUOTE]
I thought there were objections that the new rules that excluded Pluto were also sort of arbitrary. But I agree that grandfathering Pluto in makes absolutely no sense - it’s either a planet or it isn’t and there doesn’t need to be exceptions. The whole problem was that there wasn’t a clear definition of what a planet was. Creating a definition and then making up exceptions doesn’t exactly help.
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### Author:  [@Santo\_Rugger](https://boards.straightdope.com/u/Santo_Rugger)
#### Post date: [August 14, 2008, 2:04pm UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/7 "2008-08-14T14:04:32Z")
[QUOTE=kellner]
But only for a few decades, not unlike Ceres. It just happens to be the time when most people who are around now went to elemetary school.
[/QUOTE]
[When I was your age, Pluto was a planet.](http://www.new.facebook.com/login.php#/group.php?gid=2207893888)Obligatory facebook link (you may have to sign in.)
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### Author:  [@Alessan](https://boards.straightdope.com/u/Alessan)
#### Post date: [August 14, 2008, 2:08pm UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/8 "2008-08-14T14:08:13Z")
Is Jupiter a planet?
I mean, how can you call a gas giant the same thing you call a rockball like Earth? Other than the fact that they both orbit the Sun, the two bodies have nothing in common.
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### Author:  [@DrFidelius](https://boards.straightdope.com/u/DrFidelius)
#### Post date: [August 14, 2008, 2:24pm UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/9 "2008-08-14T14:24:16Z")
[QUOTE=kellner]
But only for a few decades, not unlike Ceres. It just happens to be the time when most people who are around now went to elemetary school.
[/QUOTE]
Maybe this October there will be an announcement about the world Ceres.
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### Author:  [@Kinthalis](https://boards.straightdope.com/u/Kinthalis)
#### Post date: [August 14, 2008, 2:59pm UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/10 "2008-08-14T14:59:34Z")
[QUOTE=Alessan]
Is Jupiter a planet?
I mean, how can you call a gas giant the same thing you call a rockball like Earth? Other than the fact that they both orbit the Sun, the two bodies have nothing in common.
[/QUOTE]
Well they both meet the official definition of orbiting the sun, having enough mass to overcome rigid body forces (It’s mostly round) and has cleared it’s immediate neighborhood.
If we include Pluto as a planet don’t we have to include a bunch of other objects as official planets as well?
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### Author:  [@Philster](https://boards.straightdope.com/u/Philster)
#### Post date: [August 14, 2008, 3:11pm UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/11 "2008-08-14T15:11:11Z")
[QUOTE=Alessan]
Is Jupiter a planet?
I mean, how can you call a gas giant the same thing you call a rockball like Earth? Other than the fact that they both orbit the Sun, the two bodies have nothing in common.
[/QUOTE]
Because they both fit the definition of planet. Pluto doesn’t.
See, astronomy is easy!
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### Author:  [@Mr.Excellent](https://boards.straightdope.com/u/Mr.Excellent)
#### Post date: [August 14, 2008, 3:26pm UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/12 "2008-08-14T15:26:25Z")
[QUOTE=Alessan]
Is Jupiter a planet?
I mean, how can you call a gas giant the same thing you call a rockball like Earth? Other than the fact that they both orbit the Sun, the two bodies have nothing in common.
[/QUOTE]
Sure they do - they’re both massive enough to maintain a roughly spherical shape, but not nearly massive enough to undergo nuclear fusion.
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### Author:  [@Bytegeist](https://boards.straightdope.com/u/Bytegeist)
#### Post date: [August 14, 2008, 3:33pm UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/13 "2008-08-14T15:33:25Z")
[QUOTE=Alessan]
I mean, how can you call a gas giant the same thing you call a rockball like Earth?
[/QUOTE]
The same way you can call both humans and whales “mammals”, even though the two species are noticeably different in many ways. It’s how the category _Mammal_ is defined — and as broad as that category may seem, it’s presumably defined that way for a useful purpose. The term “planet” as it’s now defined by the IAU is considered useful to astronomers.
For what it’s worth, Earth is a member of the _terrestrial planets_, whereas Jupiter is one of the _gas giants_ — when that distinction is important to make.
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### Author:  [@Oy](https://boards.straightdope.com/u/Oy)
#### Post date: [August 14, 2008, 3:38pm UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/14 "2008-08-14T15:38:05Z")
OK, how doesn’t Pluto meet the definition of a planet?
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### Author:  [@Terminus\_Est](https://boards.straightdope.com/u/Terminus_Est)
#### Post date: [August 14, 2008, 3:55pm UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/15 "2008-08-14T15:55:41Z")
[QUOTE=Derleth]
Let’s let astronomy be a science _not_ ruled by popular whim, shall we? Pluto isn’t a planet due to a reasonable and self-consistent definition of the term, not due to arbitrary decree and certainly not because anyone wants to make anyone else angry. Must everything degenerate into a popularity contest?
[/QUOTE]
The current definition of a planet was proposed during the 2006 congress of the IAU. It was approved by popular vote.
ETA: I should add that the current definition excludes Pluto as a planet.
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### Author:  [@Alessan](https://boards.straightdope.com/u/Alessan)
#### Post date: [August 14, 2008, 3:56pm UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/16 "2008-08-14T15:56:11Z")
Is, say, Mercury more similar to Jupiter than it is to Pluto? And if so, how?
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### Author:  [@Giles](https://boards.straightdope.com/u/Giles)
#### Post date: [August 14, 2008, 4:01pm UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/17 "2008-08-14T16:01:29Z")
[QUOTE=Alessan]
Is, say, Mercury more similar to Jupiter than it is to Pluto? And if so, how?
[/QUOTE]
Yes. The definition of planet includes “has cleared the neighbourhood around its orbit”: Mercury and Jupiter both satisfy this, but Pluto does not.
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### Author:  [@garygnu](https://boards.straightdope.com/u/garygnu)
#### Post date: [August 14, 2008, 4:09pm UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/18 "2008-08-14T16:09:16Z")
[QUOTE=Giles]
Yes. The definition of planet includes “has cleared the neighbourhood around its orbit”: Mercury and Jupiter both satisfy this, but Pluto does not.
[/QUOTE]
Erstwhile Doper Phil Plait, aka The Bad Astronomer, has a [retort](http://blogs.discovermagazine.com/badastronomy/2008/08/13/planet-pr0n/) to this:
> [@](#):
>
> …under the current rules, for an object to be a planet it has to be able to gravitationally sweep clean its neighborhood. That makes the Earth a planet: any asteroid or whatever that has an orbit similar to Earth’s will, over time, either hit us or get slingshot away by our gravity.
>
> But if you take Earth and put it way out in the solar system, way past Neptune, the volume of space is so much larger that an Earth-sized body cannot sweep up all the material. In that case, we could literally move Earth out a few billion kilometers, and according to the new rules it would no longer be a planet.
>
> And that’s just dumb.
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### Author:  [@Oy](https://boards.straightdope.com/u/Oy)
#### Post date: [August 14, 2008, 4:13pm UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/19 "2008-08-14T16:13:35Z")
Where do we watch this debate?
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### Author:  [@garygnu](https://boards.straightdope.com/u/garygnu)
#### Post date: [August 14, 2008, 4:19pm UTC](https://boards.straightdope.com/t/revived-question-is-pluto-a-planet/459953/20 "2008-08-14T16:19:23Z")
[QUOTE=Oy!]
Where do we watch this debate?
[/QUOTE]
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