StarWars
Postmaster
Reged: 11/26/03
Posts: 11542
Loc: At The Movies
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Astronomers say Pluto is not a planet ...... 
http://news.yahoo.com/s/ap/20060824/ap_on_sc/planet_mutiny_9
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Joad
Wordsmith
Reged: 03/22/05
Posts: 11889
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Poor Pluto: put behind the eight ball.
I don't mind, actually. The alternative was to make the definition so broad that the Solar System would have ended up quite cluttered with planets.
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Mike Casey
Postmaster
Reged: 11/11/04
Posts: 5910
Loc: Pasadena CA
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 Pluto is what it is, and not what we silly little human beings decide to call it. The Name is not the Thing!
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Mike (tVA)
All those who believe in psychokinesis, raise my hand.
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NewAstronomer
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Reged: 09/03/04
Posts: 2690
Loc: Scranton, PA U.S.A
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Quote:
Pluto is what it is, and not what we silly little human beings decide to call it. The Name is not the Thing!
Common names and definitions aid science (they simplify the topic at hand so we have a common language). For example, we call things, like our own Sun, "stars". Gigantic hot balls of gas.
Pluto is a Keiper belt object. I imagine most larger well defined solar systems (as our own) have them. "Left overs" that didn't get swept up during planetary creation phases. Nothing wrong with the definition or classification. Pluto isn't going anywhere, except in its odd non-plantery plane orbit that crosses a true planet's orbit.
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Chris
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spaceydee
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Reged: 04/16/04
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I guess it would be hyprocrital of me to resist this change.. I've always been open minded. I can't help but be upset by it, maybe it's a sign of my "age"  It still seems a bit of a waste of time though, and I think that is what bugs me the most. The study of these objects, no matter what you call them is fascinating. My concern is by "demoting" Pluto people will lose interest in studying it.
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Dee
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Joe Cipriano
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It bothers me, and I disagree with the IAU. The committee had fielded a proposal that conformed nicely with the "Occam's Razor" approach:
1. Is it round (has enough mass and gravity to overcome the molecular bonds of it's component chunks and form a sphere)?
2. Does it revolve around the Sun (rather than another planet)?
Why they didn't use this simple and succinct definition is beyond me.
So Ceres would now be a planet - so what?
The "object" has not cleared it's orbit of other junk floating around, but is sharing an orbit with that junk, so it's not a planet. Really - then we need to demote Jupiter; if it hasn't cleared its' Trojan asteroids by now, it never will...
I agree with the dissentors, and wonder how long this ruling will survive.
Pluto's still a planet. So's Sedna. And Ceres... 
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Rick Woods
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Reged: 01/27/05
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The IAU has lost considerable credibility (with me) with this announcement. Personally, I don't care what they do or don't decree. Pluto is the 9th planet. Why is this so hard for them to accept? It was a planet before there was any such thing as KBO's. Would it have been so hard to decide "they're all dwarf planets EXCEPT Pluto, which is still an official planet"?
Bah!
- Rick
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- Rick
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llanitedave
Humble Megalomaniac
Reged: 09/26/05
Posts: 10435
Loc: Amargosa Valley, NV, USA
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I agree that "clearing the orbital zone" is a bit subjective. For one thing, orbital zones change as stars evolve. There's some evidence that Uranus and Neptune were once reversed in their order from the sun compared with where they are now. They had to interact in order to switch positions. Did they lose their planetary status during that time?
As a large body starts to grow within a zone, and other bodies are incorporated into it, at what point is the zone "clear enough"? If Venus achieved its final zone clearing before earth did, does that mean that the earth, even if larger than Venus, would not yet be a planet while Venus was?
Any definition is somewhat arbitrary, that can't be helped. It seems to me, however, that this one was more arbitrary than the one that it rejected.
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Edited by llanitedave (08/24/06 06:19 PM)
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Rodders
sage
Reged: 04/23/04
Posts: 415
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It is important that we move with the times. "In life, it does not matter what we want to be true, all that matters is what is"
Common sense has prevailed here.
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Rodney
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SkyHound
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Reged: 03/20/05
Posts: 252
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Tom,
I never thought they would muck up the water more then it was but this is just a terrible definition and I'm sure won't last long. There are just to many variables that will reak havik with it.....For one thing how can this be applied to solar systems out side our own, or " planets" that have been either ejected from their home system or had there orbits changed by a near miss or collision.. The definition has to cover the evolution of a solar system not a snap shot
of any given moment.
c/s
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SkyHound
sage
Reged: 03/20/05
Posts: 252
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What is going to happen when they find the larger objects? Many Astronomers believe there may be earth size objects out behond Pluto..
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Starman1
Vendor - Scope City
Reged: 06/24/03
Posts: 10918
Loc: Los Angeles
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Quote:
What is going to happen when they find the larger objects? Many Astronomers believe there may be earth size objects out behond Pluto..
Infrared studies have ruled that out, more or less. Any body out there is likely to be smaller than Mercury.
Nonetheless, there could be hundreds of them.
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Don Pensack
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Riftcloud
sage
Reged: 05/03/06
Posts: 421
Loc: Annapolis, MD
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Pluto is and always will be the 9th planet to me! I disagree with their opinions, and feel they are overthinking it completely! It orbits the Sun, and has satellites of it's own, that's my definition of a planet... YMMV.  IAU
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Jonathan
"Research is what I'm doing when I don't know what I'm doing." - Werhner Von Braun
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Bill McHale
professor emeritus
Reged: 11/07/04
Posts: 573
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Quote:
Quote:
What is going to happen when they find the larger objects? Many Astronomers believe there may be earth size objects out behond Pluto..
Infrared studies have ruled that out, more or less. Any body out there is likely to be smaller than Mercury.
Nonetheless, there could be hundreds of them.
Yeah, that more or less thing is the problem isn't it? I am not convinced that we have done any survey's exhaustive enough to rule out the possiblity of a larger than Mercury sized object out beyond Neptune. If something was even further out than 2003UB, it seems likely it could be just as dim in the infrared as 2003UB even if it was larger.
No, I think ultimately, the current definition of planet was crafted by those who think that the idea of 10, 12 or 20 planets in the solar system is just too many as opposed to attempting to come up with a simple, easy to understand definition of a planet.
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Bill
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llanitedave
Humble Megalomaniac
Reged: 09/26/05
Posts: 10435
Loc: Amargosa Valley, NV, USA
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The main objections I have to the decision are:
1. It really doesn't say what it means by "clearing out its orbital zone." It's open to a lot of interpretation that makes it just as easy to eliminate Neptune and Jupiter as it does Pluto.
2. It very specifically states that a planet must orbit around the Sun. Capital "S". What about all those extrasolar planets that have been discovered in the last decade? Do we now have to start over thinking of new labels for them?
The whole purpose of this exercise was to take into account all the discoveries that astronomy has made recently about planetary systems, and arrive at a good, general, extensible definition. Instead, they've gone backwards and shoehorned a particular point of view into existence, one that's designed to exclude new discoveries, not accommodate them.
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"S.O.E." (Sauron's Other Eye) 16" Royce conical mirror: A permanent work in progress.
10" Homebuilt dob, old Coulter mirror
Next Project: The "Eye of Sauron" Observatory!
Edited by llanitedave (08/25/06 11:56 AM)
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Pedestal
Post Laureate
Reged: 03/11/06
Posts: 3026
Loc: Smoggy Bottom, Baytown,Texas
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Quote:
Instead, they've gone backwards and shoehorned a particular point of view into existence, one that's designed to exclude new discoveries, not accommodate them.
Perhaps I'm just too cynical: but if Pluto is a planet, "Xena" has to be a planet.
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www.smoggybottom.org
Edited by LivingNDixie (08/27/06 03:46 PM)
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Greg K.
Reged: 12/11/03
Posts: 9936
Loc: Clifton Park, NY
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Quote:
The main objections I have to the decision are:
1. It really doesn't say what it means by "clearing out its orbital zone." It's open to a lot of interpretation that makes it just as easy to eliminate Neptune and Jupiter as it does Pluto.
2. It very specifically states that a planet must orbit around the Sun. Capital "S". What about all those extrasolar planets that have been discovered in the last decade? Do we now have to start over thinking of new labels for them?
The whole purpose of this exercise was to take into account all the discoveries that astronomy has made recently about planetary systems, and arrive at a good, general, extensible definition. Instead, they've gone backwards and shoehorned a particular point of view into existence, one that's designed to exclude new discoveries, not accommodate them.
See, i don't see how this "excludes" new discoveries. It just categorizes them differently. There really is no "right" way to do it, but I'm more in favor of a defintion that reserves the term planet to the larger bodies and doesn't include every little rock or ice ball that we happen to find in orbit around the sun.
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Starman1
Vendor - Scope City
Reged: 06/24/03
Posts: 10918
Loc: Los Angeles
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Quote:
The main objections I have to the decision are:
1. It really doesn't say what it means by "clearing out its orbital zone." It's open to a lot of interpretation that makes it just as easy to eliminate Neptune and Jupiter as it does Pluto.
See post 1114071 on this thread:
Clearing out the zone
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Don Pensack
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Greg K.
Reged: 12/11/03
Posts: 9936
Loc: Clifton Park, NY
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Thanks Don,
Quote:
A planet is an end product of disk accretion around a primary star or substar. I quantify this definition by the degree to which a body dominates the other masses that share its orbital zone. Both theoretical and observational measures of dynamical dominance reveal a gap of five orders of magnitude separating the eight planets of our solar system from the populations of asteroids and comets. This simple definition dispenses with upper and lower mass limits for a planet. It reflects the tendency of disk evolution in a mature system to produce a small number of relatively large bodies (planets) in non-intersecting or resonant orbits, which prevent collisions between them.
http://xxx.lanl.gov/abs/astro-ph/0608359
It's good to see that there is a good deal more scientific rationale to the definition of "clearing out its orbital zone" than the press has reported.. That definition makes sense to me, limiting the term "planet" to those bodies formed from disc acretion.
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BillFerris
Carpal Tunnel
Reged: 07/17/04
Posts: 2576
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Quote:
Quote:
The main objections I have to the decision are:
1. It really doesn't say what it means by "clearing out its orbital zone." It's open to a lot of interpretation that makes it just as easy to eliminate Neptune and Jupiter as it does Pluto.
See post 1114071 on this thread:
Clearing out the zone
There are at least three significant problems with using this to distinguish between planets and non-planets. One, is that an earth-mass object at a great distance from the Sun has not had enough time to "clear out" its neighborhood. The second, is that we are currently unable to confirm that extra-solar planets have "cleared out" their neighborhoods. The third, is that our Solar System remains nearly unique among the know stellar systems in the Galaxy. If the purpose of adopting this new definition is, at least in part, to lay the foundation for a definition that will eventually be applicable beyond the Solar System--and the recently adopted definitions clearly do not apply beyond our solar neighborhood--then it was poor judgement on the part of the IAU to adopt a criteria may well not apply in the vast majority of stellar systems we explore.
Regards,
Bill in Flagstaff
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