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Pluto Making a Comeback
anthemaniac writes "Space.com reports that the American Astronomical Unions Division of Planetary Scientists recognizes the IAU's authority to make a new planet defintion but expects it to be altered. Separately, 300 astronomers have signed a petition saying they won't use the definition. All this stems from the discontent over how only 424 astronomers voted on the proposal that demoted Pluto. Looks like this little dog is on the comeback trail."
The publishers are loving this.
So... What is a Planet Again?
the issue centers on one the IAU itself says it hasn't addressed with it's new definition of a planet: extrasolar systems. as new telescopes come on line with more resolving power, our bestiary of planets is going to grow by leaps and bounds. it will render the debate over pluto moot
i think a definition of planet should be:
-round, with a significant atmosphere
-this is distinct from a gas giant, which should be considered closer to stars than to planets (round, mostly gas: really just stars without enough critical mass to ignite fusion)
-and distinct from a moon (no atmosphere, but still round)
-asteroids, comets, etc make up the miscellany
and notice, most importantly, i said nothing about what something orbits. what something orbits is really secondary in consideration to what something is composed of. if we find an earth-like "moon" orbiting a gas giant in another solar system, is what it orbits really the first consideration in picking what to call it? no, composition should come first, orbit second. so you could have a moon of the sun (pluto), or a planet of saturn (titan), or an asteroid of mars (deimos/ phobos, etc.)
so this system demotes not only pluto, but also mercury. while promoting titan. so our solar system is composed of:
-4 planets (venus, earth, mars, titan)
-4 gas giants (jupiter, saturn, neptune, uranus)
-and countless moons (of the sun and the planets)/ asteroids (of the sun and the planets)/ comets/ ring systems/ kuiper belt, oort cloud objects/ etc
really, as we see more and more exotic arrangements in extrasolar systems as new telescopes come on line, this debate about pluto will look more and more pedantic. and the IAU should really begin focusing on a more rigid definition no matter what, something they said they weren't doing at their last congress. we will soon have a vastly larger catalogue of strange orbital objects/ arrangements out there. pluto is small potatoes... literally
intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
Since the borderline is probably going to have to be arbitrary, why not use Pluto's diameter as the minimum? If other Kuiper objects are bigger, like Xena, then make Xena a planet also. If we end up with 20 planets, so be it. 25 is about classroom size anyhow such that each kid can get a planet assigned instead of sharing that is done now. Who knows, maybe there is a Mars-sized Kuiper object out there. Dismissing Kuiper objects just because they are "far" is kinda arbitrary. Size is a better criteria than distance.
Table-ized A.I.
I really liked the original suggestion. It's a planet if:
* It is round under its own gravity
* it is not already classified as a star
* It is not a satellite to something else not classified as a star (ie. when the common point of rotation is located within the body of the other object)
A possible fourth criteria could be:
* It orbits something classified as a star
though I'd be happy without that criteria, making solitary, wandering bodies be called planets as well.
Sure, that will probably get us planets by the dozen as we get a clearer idea of what't out in the edges of our system - but why is that a problem? It's not like having nine planets has some mysterious significance, and it hasn't been nine - or eight for that matter - for very long either.
Trust the Computer. The Computer is your friend.
. . . something you look at and say, "hey, that's a planet."
No, seriously. Given all the historical baggage surrounding the term "planet", people shouldn't be trying to use it as a scientific term in the first place. If you want something that can be used to scientifically denote a certain class of astronomical objects, call them "primary satellites" or something. What's wrong with saying something like this, for example? "A planet is one of the nine satellites of Sol: Mercury, Venus, Earth, ..., Pluto; or a similar object orbiting another star that is widely recognized as a planet." That keeps the status quo with respect to our solar system, which doesn't seem to have hurt anything in the 76 years it's been around, and lets public opinion decide on anything else that pops up. Which leaves astronomers free to spend their valuable time actually watching the sky rather than trying to convince people that something that looks like a planet and smells like a planet isn't actually a planet.
Lovell (he of canals on Mars fame) decided that there must be a huge Gas Giant out beyond Neptune, but could never find one.
In order to find this planet, and ensure that Lovell wasn't primarily remembered for his fanciful and incorrect thesis regarding life/civilisation on Mars, a junior astronomer was set to work searching for this suposed super giant Gas Planet.
Note that I say Junior, no-one else wanted the job, no-one....
Instead of a Huge Gas Giant, he found a tiny rock. As it turns out this was the first sighting of a Kuiper Belt Object, a noteworthy acheivement in itself which was sullied and robbed of its true importance as a milestone in astronomy due to the politics of the day within the astronomy movement.
So, this tiny rock was hailed as Lovells planet, in spite of the ludicrous nature of this claim, given the obvious disparity between the predicted object, and the one found. It could never have caused the gravitational perturbance by which the presence of the gas giant was inferred by Lovell.
It's status as a planet, whilst debated by some then, and many since, has been assured due to this fear of blackening Lovells name.
Interestingly, none of the astronomers who wanted Pluto to be a planet would consider calling our moon, or Ceres planets, even though admitting Pluto into the list of planets meant these, among others, would now qualify.
It is this bizarre situation that the decision regarding Pluto is seeking to resolve. That not many astronomers were there to vote is beside the point. The vote was known to be taking place a long time in advance (many months), it wasn't a rushed secret ballot or anything.
The people who want to discredit the vote don't actually have an alternative classification, they just want the ambiguity to remain.
In effect, what we have here is an old fashioned cat fight among supposedly mature people of science (predominantly men).
Oh but it is, it's very important. A precise terminology is critical to get anything done in any field.
:)
Nostalgia or neat names your kids like are no reason to violate the rules of your field. AIDS was orginally categorized as a form of cancer, but then we found that it's not a cancer, so we stopped calling it a cancer. It's simple, really. Once you disprove something, it makes no sense to go on believing it.
The simple truth is that if you call Pluto a planet, then you also have to call Ceres and potentially hundreds of bodies in the Kuiper belt planets as well. Pluto does not dominate its orbit around the sun, it shares it with Charon, they spin around each other, one is not a moon of the other. None of the other planets in the solar system have such a symbiosis, they all have moons that orbit them. What shall we do when we manage to spot specific planetary bodies in distant solar systems? "let's see... hrm, that's a class-M planet, that's a gas giant, that's a dead rock, all of these have moons and they're spherical and dominate their orbits, but hey, here's a neat looking body there dancing with another body, I guess that's a planet too, let's call it Mickey and forget the thing it's spinning with." Where does it end? We need a concise definition that works every time, no exceptions.
As it is, with that gold disc in the voyager spacecrafts showing the planets of our system, it's doubtful ET will find us now since he'll see our system has only 8 planets but his directions said there would be 9. If he stumbles into the system anyway, and finds that's he's got the right place, he's going to think we're a bunch of retards for saying we have 9 planets