IAU Rules Pluto Still a Planet

scottyscout writes "NPR reports that Pluto has dodged a bullet. An international panel has unanimously recommended that Pluto retain its title as a planet, and it may be joined by other undersized objects that revolve around the sun. Some astronomers had lobbied for reclassifying Pluto as its so tiny. And at least one major museum has excluded Pluto from its planetary display. But sources tell NPR that under the proposal, to be presented at a big meeting of astronomers in Prague next week for a vote, Pluto would become part of a new class of small planets and several more objects could be granted membership."

The Terrorists are against Pluto...

[EccentricAnomaly]

Most of the Astronomers are having trouble making it to Prague because of the security anthill that's been kicked over by the hair-gel bomb plot. This will probably have a big effect on how the IAU vote turns out.

Museum displays...

[totallygeek]

And at least one major museum has excluded Pluto from its planetary display.

Hell, I can show you museums that show kind, gentle dinosaurs living in harmony with man [answersingenesis.org]. So what?

slashdot spelling

[Anonymous Coward]

mod this down as offtopic, but it wouldn't be a /. story without spelling "it's" as "its", despite the fact that TFA is written "it is"

Re:If they have such power,,,

[mrxak]

People will debate Pluto's class until the end of the solar system. This is not a new story, in the sense that this is not the first time Pluto's status has been discussed. I think it should just be grandfathered in, if anything. Plus we have a bunch of other objects out there that could be considered planets too. Sedna, Xena, Quaoar, Varuna, Ixion... what do we do with those?

Excellent picture

[LotsOfPhil]

So Pluto has 3 moons? I had never seen this picture before and think it is very cool.
Pluto via Hubble [npr.org]

Inaccurate

[Zenaku]

The headline and summary are extremely misleading. The agency hasn't ruled at all. The vote is yet to come. All that has happened is that a panel of 7 people has made a recommendation, which may or may not be excepted. And the recommendation has plenty of problems that might prevent it from passing a vote. From TFA:

The panel's recommendation is being reviewed by the International Astronomical Union's executive committee. In an interview last week, executive committee member Bob Williams said the definition proposed by the panel had some potential problems, and he was not at all sure if the astronomers voting in Prague this month would approve it.

"At this point, I don't feel confident enough to bet in favor of it," he said.

More than just tiny

[mshurpik]

It's more than Pluto being tiny. Pluto has a highly elliptical, out-of-plane orbit that crosses over Neptune's orbit, AND its orbit is 3/2 in phase with Neptune, suggesting that it was captured by Neptune's gravity.

Is a "planet" something that was created with the solar system, or is a "planet" simply something that has a moon? Right now, we're using the latter definition.

If you want to see another example of scientific retrenchment, check out Phylocode. For years biologists have been classifying species on a Linnaean 2D grid, inheritance and time, as if God somehow keeps all his evolutions in perfect lockstep. Phylocode, tree-based, uses the inheritance dimension only.

Re:More than just tiny

[Anonymous Coward]

Pluto has a highly elliptical, out-of-plane orbit that crosses over Neptune's orbit, AND its orbit is 3/2 in phase with Neptune, suggesting that it was captured by Neptune's gravity.

Not quite, Pluto actually formed in the original Kuiper Belt [wikipedia.org], making it part of the original Solar System, not an object captured by Neptune. Its current orbit is the result of Neptune's gravity, yes, but Pluto was formed in orbit of the sun.

Is a "planet" something that was created with the solar system, or is a "planet" simply something that has a moon? Right now, we're using the latter definition.

Actually, neither Mercury nor Venus have moons, yet they're accepted as planets. The problem is not that an "incorrect" definition of planet is being used, it's that there is no clear definition of what constitutes a planet. This recommendation (the title is misleading, as no actual ruling was handed down) is merely part of a much larger debate on the definition of a planet [wikipedia.org].

Re:Why not fix the "official" number of planets

[susano_otter]

Not really. "pi" is a mathematical constant, that describes a specific, precise, and unmistakable relationship between a platonic circle and its radius.

"Planet", on the other hand, is an arbitrary term, convenient for differentiating between different types of celestial bodies, but not actually bound to a specific natural phenomenon or physical law or mathematical principle.

Re:More than just tiny

[Anonymous Coward]

...or is a "planet" simply something that has a moon? Right now, we're using the latter definition.

Venus and Mercury would suggest otherwise.

Nonsense.

[porkchop_d_clown]

The truth of the matter is that Pluto is a KBO but every time the popular press runs an article pointing that out, astronomers are flooded with calls from Auntie Mabel demanding to know where they get off changing what she learned in school.

This isn't even remotely like a dispute between two theories - it's a simply argument over nomenclature and science has no problem at all simultaneously supporting multiple naming conventions.

Re:I don't get it

[Jugalator]

Because there's nothing the scientific community loves more than controversy

I thought the set of planetary "rules" should be generic and work for our solar system to avoid controversies.

Scientists generally hate controversies as far as I know. That's why they try to search for unifying theories and theories that work, instead of keeping to invent random unprofessional theories to challenge other established ones with.

Ymir was a giant . . .

[j_w_d]

not a midget.

Pluto, the definition of a planet, and the IAU

[chongo]

BTW: This is not intended to be a complete history of the topic, I'm only pointing out a few highlights that others might find interesting.

A number of years ago, the question of a definition of a planet was raised as a result of discoveries of "planets" outside of our solar system as well as a growing number of Kuiper Belt Object (KBO) discoveries in our solar system. The IAU Division of Planetary Systems Sciences technical committee wisely chose to delay a decision on a definition until a more significant body of data was obtained.

In the mean time, a well meaning but widely misunderstood suggestion from an esteemed Astronomer suggested that the planet Pluto also be given a nice round minor planet number (i.e., reserve the next multiple of 10000). His intent was to recognize the special nature of Pluto as a large member of the KBO (Kuiper Belt Object) family. He never intended to demote Pluto from planet status. However, the press took the phrase "making Pluto a minor planet" and blew the controversy way out of proportion.

An executive committee recommendation on Planet definition was formed to draft a proposal for a definition of a planet. Minutes from the IAU executive committee indicated that they favored definitions that were based on measurable physical properties over arbitrary values. For example, they signaled that they were NOT inclined to look favorably on proposals such as "limit the number of 9 planets", or proposals that set an arbitrary minimum size of a Planet.

Last January at the AAS conference, an IAU liaison announced that the IAU executive committee was scheduled to produce a report on its recommendations just prior to the IAU 26th IAU General Assembly in Prague (Aug 14 to 25, 2006). The liaison recommended that any final comments and recommendations be submitted to the exectuive committee at least a month prior to the IAU general assembly.

I was part of a group that submitted a recommendation that the definition of a Planet encompass a requirement that "it must orbit a primary fuser with sufficient mass to deform it into an spheroidal / oblate spheroidal shape". We realized that our proposal could result in redefining several bodies as planets including the large asteroid Ceres. We proposed that a new sub-class of Planets could be defined (again based on measurable physical properties) to acuminate these new dwarf planets.

We were told that a number of other groups had submitted similar of very similar proposals. I have not examined the executive committee report in detail, however it appears that IAU executive committee agrees, in principle, with such proposals.

On Tuesday 2006 August 22, 12:45-13:45 (local Prague time), in Forum Hall, executive committee recommendation on Planet definition will be presented. Based on the unanimous recommendation of the executive committee, I am hopeful of a favorable outcome form the IAU General assembly.