This sounds like a grammar school question. Nevertheless Correia et al. (below) just posted their discovery of a 3:2 mean motion resonance in a planetary system, far, far away.
I belatedly vote to have Pluto back.
The Neptune Pluto couple should be high in our list of things to know, even since our grammar school days. This way any of these pairs we discover can be easily analyzed once we remember everything there is to know about our own synchronous pair!
Correia et al. write:
"It is quite remarkable that, in contrast to the findings of
Correia et al. (2005) for the 5:1 resonance in the HD202206 system, there is perfect coincidence between the stable 3:2 resonant islands, and curves of minimal χ2 obtained in comparing with the observations. Since these islands are the only stable zones in the vicinity, this picture presents a very coherent view of dynamical analysis and radial velocity measurments, which reinforces the confidence that the present system is in a 3:2 resonant state."
Chaos Theory is good to know that exoplanets are stable. I did not imagine that!
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2 comments:
Pluto IS a planet because unlike most objects in the Kuiper Belt, it has attained hydrostatic equilibrium, meaning it has enough self-gravity to have pulled itself into a round shape. When an object is large enough for this to happen, it becomes differentiated with core, mantle, and crust, just like Earth and the larger planets, and develops the same geological processes as the larger planets, processes that inert asteroids and most KBOs do not have.
Not distinguishing between shapeless asteroids and objects whose composition clearly makes them planets is a disservice and is sloppy science.
As of now, there are three other KBOs that meet this criterion and therefore should be classified as planets—Haumea, Makemake, and Eris. Only one KBO has been found to be larger than Pluto, and that is Eris.
The IAU definition makes no linguistic sense, as it states that dwarf planets are not planets at all. That’s like saying a grizzly bear is not a bear. Second, it defines objects solely by where they are while ignoring what they are. If Earth were placed in Pluto’s orbit, by the IAU definition, it would not be a planet. That is because the further away an object is from its parent star, the more difficulty it will have in clearing its orbit.
Significantly, this definition was adopted by only four percent of the IAU, most of whom are not planetary scientists. No absentee voting was allowed. It was done so in a highly controversial process that violated the IAU’s own bylaws, and it was immediately opposed by a petition of 300 professional astronomers saying they will not use the new definition, which they described accurately as “sloppy.” Also significant is the fact that many planetary scientists are not IAU members and therefore had no say in this matter at all.
Many believe we should keep the term planet broad to encompass any non-self-luminous spheroidal object orbiting a star.
We can distinguish different types of planets with subcategories such as terrestrial planets, gas giants, ice giants, dwarf planets, super Earths, hot Jupiters, etc.
We should be broadening, not narrowing our concept of planet as more objects are being discovered in this and other solar systems.
In a 2000 paper, Dr. Alan Stern and Dr. Hal Levison distinguish two types of planets—the gravitationally dominant ones and the smaller ones that are not gravitationally dominant. However, they never say that objects in the latter category are not planets.
I attended the Great Planet Debate, which actually took place in August 2008, and there was a strong consensus there that a broader, more encompassing planet definition is needed. I encourage anyone interested to listen to and view the conference proceedings at http://gpd.jhuapl.edu/ You can also read more about this issue on my blog at http://laurele.livejournal.com
You can find the petition of astronomers who rejected the demotion of Pluto here: http://www.ipetitions.com/petition/planetprotest/
Ms. Kornfeld:
I am so glad you wrote this here. I hadn't followed the controversy, and when I read Correia et al.'s article, I felt that maybe the decision to demote Pluto was wrong.
Now I am almost convinced it was wrong.
Thank you so much!
Eduardo
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