A little off topic today, but I have a question for the IAU about their decision to demote Pluto from a full-fledged card-carrying member of the planetary club to merely a wanna be.... a hanger on from the edge of the solar system.
I know this discussion is a bit like beating a dead horse, after all, no matter what things the New Horizons probe finds out when it arrives in 2015 is going to change the fact that Pluto is no longer a planet... but I still want to ask anyway.
The definition of what now constitutes a planet is something that circles the sun, has enough gravity to pull itself into a spherical shape and also manages to clear its orbit of other bodies. Pluto is not a planet because it hasn't cleared Neptune from its path? What about Neptune? Neptune has failed to clear Pluto from its path, so do we demote it? How could we, after all, its a gas giant and certainly can't be demoted... but Pluto is an oddball... the black sheep of the family so to speak.
But that's not the reason I have against the demotion. No, my question has to do with Lagrange points.
Lagrange points are like eddies in the orbits of planets (so far discovered in our own orbit, as well as that of Mars, Neptune and Jupiter). These points in space are a balance where bits of celestial bodies (called Trojans) can gather, either leading the planet or following at fixed points that can be determined mathematically. Earth has one Trojan than we know of so far, but Jupiter has a load of these both leading and following in its wake.
So here is my question.
If the definition of a planet is something that has cleared its orbit.... what about these bodies lounging in our Lagrangian points? If you take the IAU at face value, then Jupiter isn't a planet because it still has thousands of Trojans still in its orbital path. Neptune isn't a planet because not only has it failed to clear Pluto from its path, but it also has Trojans in its orbit. Heck, Earth isn't even a planet now because we have a body called Cruithne that doesn't appear to be a true Trojan, but is still using one of our L.P.s as the fulcrum of its own short orbital path. So if you discredit Trojans from the things that need to be cleared, why excuse the Earth, because Cruithne isn't a true Trojan after all. Which is a moot argument for Earth anyway seeing as how our own moon is slowly drifting away from us at a rate of about 4 cm a year. It'll take awhile, but eventually our own moon is going to wander off... so, wait... does it mean that we are not only so wimpy that our gravitational pull can't hold onto our one and only satellite, but that we aren't clearing it from our path as well?
So why not demote more of our planetary system as planets, since many of them don't follow the rules either?
Is it the atmosphere thing? Well that can't be, because Pluto does have an atmosphere... at certain points of its orbit when the temperature warms up enough during its closest approach to the sun the frozen atmosphere thaws and returns to its gaseous state. As it moves away from the sun the atmosphere (such as it is) freezes and falls back onto the planet. Which means it could be said that Pluto, in a warped sense of the word, has seasons.
So after the demotion, people tried saying that Pluto was now part of the Kuiper Belt.... but Pluto only shares part of its elliptical orbit with the Kuiper Belt.... the K.P. has a circular orbit, not elliptical. And Neptune's orbit is actually within the K.P. At least one of its own moons is thought to be a stolen K.P. object. So did Neptune kick it out of the K.P. and send it on its current path? But then, why would Pluto have its own satellites? Not only does Pluto have its large moon Charon, but it also has the smaller satellites Nix, Hydra and the blah sounding S/2011 P1. So wait, Pluto and a bunch of smaller units were tossed out together and yet managed to form their own little planetary unit?
Not that I expect anyone to answer this little conundrum, but it really would be nice to have some authority on hand that could actually explain the rationalization behind Pluto's demotion despite some pretty compelling evidence.
I do look forward to July of 2015 when New Horizons will be able to give us further insights to this fascinating little puzzle piece. Even if Pluto is no longer considered a "real planet" at least it is still a planet in the hearts of its fans. Regardless of its status now or in the future, Pluto will keep spinning on, not caring in the least what label we lay on it.
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