geekyIt could be that only astronomers, astronomy buffs, or kids really give a hoot whether Pluto is a planet or not. I’m at least one of those, but I’ll try to explain this is a way that won’t bore the rest of you.
I’m not talking about the big, goofy Disney dog Pluto (who can’t talk, even though the big, goofy Disney dog Goofy can; what’s up with that?) Pluto is – was – the ninth planet in our solar system; it’s always been odd, kind of like your older Uncle Edgar, who shows up at family reunions without pants and isn’t allowed near kids or cats.
The inner planets are more of a big deal to the human race, since we’re on one (Earth is no more flat than Dolly Parton). Those planets may someday provide us with resources, or even another place to live. It’ll be like trashing your home and, instead of bothering to clean, just moving to a new one. Maybe we can leave the Earth to people who litter, blow each other up, and don’t use turn signals.
Further out are the gas giants, which may someday give us gas. There will be no discussion here on how to pronounce Uranus, but for the curious – yes, there is a ring around it.
Astronomers speculated there must be another planet beyond those, based on tiny perturbances to the orbits of the first eight. It never occurred to anyone that the orbit fluctuations might be the influence of rock and roll, possibly Elvis gyrations.
When someone found Pluto in 1930, they declared it a planet, and happily went on with their debate over whether there’s a black hole on – nah, I can’t do it. Family paper.
Unfortunately, it turned out the new mass was smaller than expected, and was actually divided into two bodies: Pluto and its moon, Charon. I’d have named it Goofy, but never mind. (Recently it was learned that Pluto has two other, tiny moons, which I shall call Mickey and Minnie.)
So Pluto was smaller than many moons orbiting other planets, including our moon, which is called … well … the Moon. Still, it was there, and it was orbiting the sun that we call the Sun, so what the heck.
Then they found Xena. Its real name is 2003 UB, but I think you’ll agree Xena, which turned out to be bigger than Pluto, is much more fun.
Yay! A tenth planet!
Then they found another one. And another. Still another was nicknamed Buffy, because it was in such an odd, tilted orbit that it slayed all the popular theories about how these objects were formed. Get it? Buffy the Theory Slayer? Ah, never mind.
So many of these objects started turning up that astronomers realized they were dealing with a whole cloud of orbiting objects, which they named the Kuiper Belt after … come on, don’t make me say it. First name Gerard …
Now scientists believe there are thousands of Kuiper Belt Objects (KBO’s, not to be confused with the thousands of HBO’s in the Cable Belt). Some are larger than Pluto.
Add that to the fact that Pluto’s orbit is eccentric (see above about Uncle Edgar) compared to the normal planets, and the question arises: Is Pluto a planet? If it isn’t, what is it?
Astronomers had never gotten around to defining a planet, so when they did a big fight started between the Pluto Planeteers and the Pluto Plunderers, and we’ll have the highlight reel at eleven.
One group of scientists thinks any object big enough to be formed by gravity into a sphere is a planet, if it isn’t orbiting another planet. Then it got complicated. If a pair of objects were close enough together in size that they revolved around a central point in space, rather than one circling the other, they were both planets; a duel planetary system. This would make Pluto and Charon planets, while the larger Moon, because it orbits the great big honkin’ Earth, would remain the Moon.
Let me catch my breath, here.
That would make 12 known planets in our system: the 9 we knew about, plus Charon, Xena, and the asteroid Ceres. But there were already twelve other asteroids that were well rounded, like me after Thanksgiving dinner, and could be candidates for planethood. In fact, there might be as many as 53 known bodies that fit the description, and more yet to be discovered.
Okay, kiddies; today in science, we’re going to memorize the names of the fifty-three honkin’ planets. Ready?
So the astronomers with poor memory came up with a new idea. Yes, planets had to be in orbit around the sun and be round; but they also had to have gravity strong enough to “clear the neighborhood”. That means any other objects orbiting in the same area would either be pulled into the planet, or thrown out of the area entirely. Pluto’s surrounded by all sorts of objects – it’s throwing a party way out there. Its amazing Neptune hasn’t called in a complaint.
So Pluto’s not a planet, nor is Xena, or anything else in various belts. There are only 8 planets – finally, today’s school kids get a break. And what of Pluto?
If it’s big enough to be round, it’s a dwarf planet. Right now there are three – Pluto, Ceres, and Xena – but if there’s any justice in this universe at all, we’ll discover there are 7 dwarfs orbiting our snow white star. (Okay, it’s yellow – whatever.) Anything that’s in orbit, but too small to be round, will be called a “small solar system body”, which would cover asteroid and comets.
How does all this matter to you and me? Well, it doesn’t, really. But as an engine of imagination, something to get the young future scientists out there interested in the universe, it’s really big. Some kid entering first grade today may be the one who discovers another ninth planet, or lands on Mars, or discovers intelligence on Uranus.
Doesn’t that stimulate your imagination?