Do It For The Children

One of the greatest debates of our time rages on among the scientists and astronomers: Is Pluto a planet, and if so, what guidelines should be set for including or excluding other celestial bodies? One side says that it shouldn’t be a planet because it’s too small, it’s thoroughly unlike the four preceding planets in composition, and its orbit is skewed so that it sometimes passes closer to the sun than its neighbor Neptune. The other side says that it is a planet because it was not formed by the process that makes stars, gravity is responsible for its shape, it has a little moon, and, well… it orbits the sun. The problem is the Kuiper Belt. It’s a region of space beyond Neptune’s orbit that is populated by thousands of rocks, comets, and other little pieces of stuff. Pluto is on the inner limits of the Kuiper Belt, and for many years it’s been both the 9^th Planet and a Kuiper Belt Object. So where does the line get drawn?

Interestingly enough, last year an astronomer discovered an object beyond Pluto’s orbit that also orbits the sun. Turns out that it’s bigger than Pluto and made of the same stuff. The object – officially named 2003 UB313 for now, but the guy who discovered it calls it Xena (yes, after the warrior princess) – is also part of the Kuiper Belt. Therefore, if Pluto remains an official planet, would Xena become the 10^th planet? It would only be fair to her/it! And then what’s stopping the astronomers from naming the 20-30 other large Kuiper Belt Objects as planets? The flip side is that if Xena is discounted from being an official planet, then Pluto should also be discounted (along with all other KB Objects) and we’d have a solar system with eight planets.

I think the debate is fascinating, and it shows that nothing is static amongst the astronomers. The big poster I had when I was a kid showed nine planets, but I was recently at the Hayden Planetarium in NYC and guess what? Pluto is nowhere to be found. I’m definitely of the opinion that Pluto remain a planet – why can’t there be more than one kind of planet? Jupiter, Saturn, Uranus, and Neptune can be “gas planets” (especially Uranus – there’s a gaseous name), and Pluto, Xena, and other KB Objects can be “ice planets.” Imagine the science fiction stories that would arise if the solar system suddenly included 37 planets.