Skip to comments.Pluto Could Lose Planet Status
Posted on 06/22/2006 4:11:12 AM PDT by PatrickHenry
At its conference this August, the International Astronomical Union (IAU) will make a decision that could see Pluto lose its status as a planet.
For the first time, the organisation will be officially defining the word "planet", and it is causing much debate in the world of astronomy.
There is only one thing that everyone seems to agree on: there are no longer nine planets in the Solar System.
The debate has been brought to a head by the discovery of a potential 10th planet, temporarily named 2003 UB313 in January 2005. This new candidate planet is bigger than Pluto.
The question now facing the IAU is whether to make this new discovery a planet.
Pluto is an unusual planet as it is made predominantly of ice and is smaller even than the Earth's Moon.
There is a group of astronomers that are arguing for an eight-planet SolarSystem, with neither Pluto or 2003 UB313 making the grade as a planet; but a number of astronomers are arguing for a more specific definition of a planet.
One of these; Kuiper Belt researcher Dr Marc Buie, of the Lowell Observatory in Arizona, has come up with a clear planetary definition he would like to see the IAU adopt.
I believe the definition of planet should be as simple as possible, so I've come up with two criteria," he said.
"One is that it can't be big enough to burn its own matter - that's what a star does. On the small end, I think the boundary between a planet and not a planet should be, is the gravity of the object stronger than the strength of the material of the object? That's a fancy way of saying is it round?"
This definition could lead to our Solar System having as many as 20 planets, including Pluto, 2003 UB313, and many objects that were previously classified as moons or asteroids.
One possible resolution to the debate is for new categories of planet to be introduced. Mercury, Venus, the Earth and Mars would be "rocky planets". The gas-giants Jupiter, Saturn, Uranus and Neptune would be a second category.
Whatever the outcome of this debate there is only one thing that we can be certain of; by September 2006 there will no longer be just nine planets in our Solar System.
Sol and Luna are Latin.
If the term is man-made, and refers to no objective and universal reality, then how can you know that we're both speaking of the same thing when we use the term "planet," or any other term?
The fact is that scientists, like all people, can't help but use terms when speaking. If terms do not refer to universals or essences, then we're left with nominalism and ultimately solipsism or absolute skepticism.
I realize that you have no interest in Aristotelianism and Thomism, but I post this info for the benefit of others.
Antichthon was the counter-earth in an earlier scheme.
Teach the controversy!
What about Planet Claire?
What if we call it a tiny brown dwarf star?
That would be consistent with the link you posted where they named a Jupiter sized object incapable of fusion orbiting another star a brown dwarf. But I don't like it for two reasons.
Jupiter is in our back yard and has been a planet all this time. I don't really want to be in a two star system, especially if one star is a dud.
Which brings me to the second reason. Stars ought to glow. I think one of the defining characteristics for a star should be that it produces visibile light. Or at least produced light at one time and burned out.
In what wavelength? Even the earth glows in infrared, microwave and radio.
But that's the problem planetary scientists find themselves in. They have a lot more data now and there are objects that cover every size from a pimple to galactic superclusters.
I think they should make a contest out of what to call all these objects and give away scholarship money to kids for science degrees. ;)
Visible spectrum. There's bound to be some object that glows barely, so some definite measure of luminosity in the visible spectrum should be set.
"They have a lot more data now and there are objects that cover every size from a pimple to galactic superclusters."
yeah, which is why they really need to come up with some definitions. Even if they end up tweaking them later. Up till now, I think they've relied on obvious differences. Planets were clearly not stars, asteroids were clearly not planets. Comets were neither. And then there was pluto.
I like your idea of the contest.
13 Jupiter masses are required for deuterium fusion.
Planets have less mass.
Brown dwarf stars have more and may only burn briefly (~10 million years).
That is the cutoff. (see my other posts re moons and low end planets)
Pluto Might Have Rings
Space.com | 22 February 2006 | Ker Than
Posted on 02/23/2006 1:16:50 PM EST by nickcarraway
Pluto Has Three Moons, Hubble Images Show
ap on Yahoo | 10/31/05 | Alex Dominguez - ap
Posted on 10/31/2005 9:22:32 PM EST by NormsRevenge
Rethinking the Planets
Popular Science | January 2006 issue (I believe) | Michael Stroh
Posted on 12/28/2005 5:36:18 PM EST by SunkenCiv
10 Planets? Why Not 11?
NY Times | August 23, 2005 | KENNETH CHANG
Posted on 08/23/2005 7:39:11 PM EDT by neverdem
and just for fun:
2012: the piano-sized New Horizons probe of NASA nears Pluto (will it find ET there?)
India Daily | Jan. 6, 2006
Posted on 01/10/2006 11:29:19 AM EST by presidio9
|"To Pluto And Far Beyond" By David H. Levy, Parade, January 15, 2006 -- We don't have a dictionary definition yet that includes all the contingencies. In the wake of the new discovery, however, the International Astronomical Union has set up a group to develop a workable definition of planet. For our part, in consultation with several experienced planetary astronomers, Parade offers this definition: A planet is a body large enough that, when it formed, it condensed under its own gravity to be shaped like a sphere. It orbits a star directly and is not a moon of another planet.|
The discovery of 2003 UB313, the 10th planetIs this object really a planet? Is Pluto a planet? What makes a planet?
by Michael Brown
Even after all of these years of debate on the subject of whether or not Pluto should be considered a planet, astronomers appear no closer to agreement. I wrote extensively about this at the time of the discovery of Sedna in March 2004. My thoughts have evolved since then, so it might be amusing to see what I said 1 1/2 years ago... The main stumbling block in defining planets in our solar system is that, scientifically, it is quite clear that Pluto should certainly not be put in the same category as the other planets... There is no good scientific way to keep Pluto a planet without doing serious disservice to the remainder of the solar system. Culturally, however, the idea that Pluto is a planet is enshrined in a million different ways, from plastic placemats depicting the solar system that include the nine planets, to official NASA web sites, to mnemonics that all school children learn to keep the nine planets straight, to U.S. postage stamps. Our culture has fully embraced the idea that Pluto is a planet and also fully embraced the idea that things like large asteroids and large Kuiper belt objects are not planets. In my view scientists should not be trying to legislate an entirely new definition of the word "planet." They should be trying to determine what it means. To the vast majority of society, "planet" means those large objects we call Mercury through Pluto. We are then left with two cultural choices. (1) Draw the line at Pluto and say there are no more planets; or (2) Draw the line at Pluto and say only things bigger are planets. Both would be culturally acceptable, but to me only the second makes sense for what I think we mean when we say the word planet... Thus, we declare that the new object, with a size larger than Pluto, is indeed a planet. A cultural planet, a historical planet. I will not argue that it is a scientific planet, because there is no good scientific definition which fits our solar system and our culture, and I have decided to let culture win this one. We scientists will continue our debates, but I hope we are generally ignored.
I agree with you, and so does David Levy and Michael Brown. :')
Not only that, but Pluto is much too interesting to be dismissed as a planet: 3 moons, an atmosphere, its history either as a former moon of Neptune or having been placed in its current orbit by an encounter with Neptune and, culturally, we have a spacecraft en route to it.
Yeah, but with the Klingons in the way, it could be a sticky situation.
I think that we might consider designating Massachusetts as the new "ninth planet" in the case that we do lose Pluto!
Gas giants. Doesn't seem appropriate that Uranus is a gas giant?
Classical astrology didn't even include Uranus and Neptune.
Pluto is the only planet discovered by an American. If it had been discovered by a Mayan or an Aztec or an African, I doubt that we'd be having this conversation right now.
At one time the asteroid Ceres was considered a planet, but when dozens (now thousands) of similar "main belt" asteroids were found, it was demoted.
Clearly, one way, the current way, to define planets is by roster. I'm just glad that Clyde Tombaugh didn't live to see this day.
And perhaps a ring. I'd not be surprised if more moons / moonlets are found. Boring old tiny little Pluto will wind up one of the most interesting, precisely because of where it is and (by 2012) its many siblings (such as Brown's Planet, Quaoar, Sedna, 2003 EL61, 2004 DW, and those to come in the next six years).
The satellites of Neptune and the origin of Pluto
Authors: Harrington, R. S.; van Flandern, T. C.
Thanks. Let's wait until they make a decision. Then a new thread will be appropriate.