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Woot: Pluto's [NOT] a Planet

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Woot: Pluto's [NOT] a Planet

Old 08-16-06, 08:56 AM
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Woot: Pluto's [NOT] a Planet

The International Astronomical Union (IAU) has a draft resolution to define a planet. It will be voted on later this month. Some articles explain it poorly, so here is the draft itself. The link has several other useful links:
http://www.space.com/scienceastronom...esolution.html

The IAU Planet Defintion Draft Resolution

posted: 16 August 2006 2:00 am ET

Editor's Note: This is the full text of a proposal for the definition of a planet released today by the International Astronomical Union (IAU) after recommendations from a seven-member committee.

Draft Resolution 5 for GA-XXVI: Definition of a Planet

Contemporary observations are changing our understanding of the Solar System, and it is important that our nomenclature for objects reflect our current understanding. This applies, in particular, to the designation "planets". The word "planet" originally described "wanderers" that were known only as moving lights in the sky. Recent discoveries force us to create a new definition, which we can make using currently available scientific information. (Here we are not concerned with the upper boundary between "planet" and "star".)

The IAU therefore resolves that planets and other Solar System bodies be defined in the following way:

(1) A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape (1), and (b) is in orbit around a star, and is neither a star nor a satellite of a planet. (2)

(2) We distinguish between the eight classical planets discovered before 1900, which move in nearly circular orbits close to the ecliptic plane, and other planetary objects in orbit around the Sun. All of these other objects are smaller than Mercury. We recognize that Ceres is a planet by the above scientific definition. For historical reasons, one may choose to distinguish Ceres from the classical planets by referring to it as a "dwarf planet." (3)

(3) We recognize Pluto to be a planet by the above scientific definition, as are one or more recently discovered large Trans-Neptunian Objects. In contrast to the classical planets, these objects typically have highly inclined orbits with large eccentricities and orbital periods in excess of 200 years. We designate this category of planetary objects, of which Pluto is the prototype, as a new class that we call "plutons".

(4) All non-planet objects orbiting the Sun shall be referred to collectively as "Small Solar System Bodies". (4)


--------------------------------------------------------------------------------

(1) This generally applies to objects with mass above 5 x 10^20 kg and diameter greater than 800 km. An IAU process will be established to evaluate planet candidates near this boundary.

(2) For two or more objects comprising a multiple object system, the primary object is designated a planet if it independently satisfies the conditions above. A secondary object satisfying these conditions is also designated a planet if the system barycentre resides outside the primary. Secondary objects not satisfying these criteria are "satellites". Under this definition, Pluto's companion Charon is a planet, making Pluto-Charon a double planet.

(3) If Pallas, Vesta, and/or Hygeia are found to be in hydrostatic equilibrium, they are also planets, and may be referred to as "dwarf planets".

(4) This class currently includes most of the Solar System asteroids, near-Earth objects (NEOs), Mars-, Jupiter- and Neptune-Trojan asteroids, most Centaurs, most Trans-Neptunian Objects (TNOs), and comets. In the new nomenclature the concept "minor planet" is not used.
Old 08-16-06, 09:29 AM
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Does this mean that Earth-Moon is now a double planet?

The moon has a mass of 7.349e+22 kg.

http://www.solarviews.com/eng/moon.htm#stats
Old 08-16-06, 09:39 AM
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Originally Posted by Nick Danger
Does this mean that Earth-Moon is now a double planet?

The moon has a mass of 7.349e+22 kg.
Originally Posted by Some Science Shit
(b) is in orbit around a star, and is neither a star nor a satellite of a planet.
So, no.
Old 08-16-06, 09:52 AM
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Every now and then you come across a news item that shakes your soul and revamps your entire philosophical outlook on life and your place in the universe.

This is not one of those items.

"... a rose by any other name ..."
Old 08-16-06, 09:56 AM
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So is this going to throw all those wacko astrology charts off?
Old 08-16-06, 10:01 AM
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Even Mike Brown (discovered UB313 - aka "Xena") disagreed with proposal.

That would make Caltech researcher Mike Brown, who found 2003 UB313, formally the discoverer of the 12th planet. But he thinks it's a lousy idea.

"It's flattering to be considered discoverer of the 12th planet," Brown said in a telephone interview. He applauded the committee's efforts but said the overall proposal is "a complete mess." By his count, the definition means there are already 53 known planets in our solar system, with countless more to be discovered.
Source: http://www.msnbc.msn.com/id/14364833/
Old 08-16-06, 10:15 AM
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Oh great, now planets are going to be coming out of the woodwork!

They should just send those planets back to the country they came from.
Old 08-16-06, 10:15 AM
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Originally Posted by Mike Brown, paraphrased
By his count, the definition means there are already 53 known planets in our solar system, with countless more to be discovered.
Oh man, can you imagine the kids' science fair projects? No more day-before-quick-solar-systems. They'd have to start a week earlier.
Old 08-16-06, 10:17 AM
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What about requiring that a planet has to have some sort of atmosphere? Would that cut it down from 53?
Old 08-16-06, 10:21 AM
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Originally Posted by Tracer Bullet
What about requiring that a planet has to have some sort of atmosphere? Would that cut it down from 53?
Wouldn't that kick Mercury out of the club?
Old 08-16-06, 10:25 AM
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Originally Posted by VinVega
Wouldn't that kick Mercury out of the club?
It has one, but it's not there in any significant amount.
Old 08-16-06, 10:26 AM
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Originally Posted by dtcarson
Oh man, can you imagine the kids' science fair projects? No more day-before-quick-solar-systems. They'd have to start a week earlier.
That is exactly what I was thinking of as well! I did the same thing back in elementary school.
Old 08-16-06, 10:38 AM
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Actually, the IAU is talking about reclassifying something about the size of Pluto or slightly smaller under the proposed name Plutons and not as true planets. That would encompass Pluto, Sedna and the so-called "Xena."
Old 08-16-06, 10:56 AM
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They're all just Kyper belt objects for the most part. Personally I think they should all be classified as such and left it at that.
Old 08-16-06, 11:07 AM
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Originally Posted by Kittydreamer
They're all just Kyper belt objects for the most part. Personally I think they should all be classified as such and left it at that.
I always knew Kittydreamer was a closet Planet hater.
Old 08-16-06, 11:11 AM
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Originally Posted by VinVega
I always knew Kittydreamer was a closet Planet hater.
No, I'm just too much of a science nerd and know too much about these things. Too many space programs on the science channel....
Old 08-16-06, 11:12 AM
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Aka, Planet X
Old 08-16-06, 11:20 AM
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I think any "planet" should have the following:

- mass significant enough to be (more or less) spherical
- coplanar, (more or less) circular orbit

That includes Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune, but excludes Pluto and the rest.

Originally Posted by Kittydreamer
They're all just Kyper belt objects for the most part. Personally I think they should all be classified as such and left it at that.
Kuiper
Old 08-16-06, 11:25 AM
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Just sort everything by size, divide into ten categories and label them. "Class A" object, "class b" object, and so on. The nine planets would be a quaint archaism. What's so hot about qualifying as a planet, anyway? Do you get more grants?
Old 08-16-06, 11:38 AM
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Originally Posted by Mrs. Danger
Just sort everything by size, divide into ten categories and label them. "Class A" object, "class b" object, and so on. The nine planets would be a quaint archaism. What's so hot about qualifying as a planet, anyway? Do you get more grants?
Yup, it all comes down to money sadly.
Old 08-16-06, 11:38 AM
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Why is Charon (formerly Pluto's moon) now possibly a planet? This is the official explanation...

A secondary object satisfying these conditions is also designated a planet if the system barycentre resides outside the primary.

...my response is, huh? Does Charon not orbit around Pluto or something?
Old 08-16-06, 11:52 AM
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LONG LIVE THE OORT CLOUD!!!!

Puny Planets
Old 08-16-06, 11:56 AM
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Originally Posted by Nick Danger
Does this mean that Earth-Moon is now a double planet?

The moon has a mass of 7.349e+22 kg.

http://www.solarviews.com/eng/moon.htm#stats
No, you have to look at the barycenter or center of mass of the pair. If it lies inside the primary (the larger), the secondary is a moon. If it is exterior to the larger planet (not so for Earth-moon), they are coplanets.

In the case of Pluto-Charon, this test makes Charon a co-planet.
Old 08-16-06, 11:58 AM
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Originally Posted by Breakfast with Girls
I think any "planet" should have the following:
The only thing required should be intelligent life.

Then, the only debatable possibility would be Earth.
Old 08-16-06, 12:07 PM
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