When Pluto was a Planet


pluto

My daughter, a kindergartener, told me about the 8 planets in our solar system, and she could name them in order. At first I was thrown off. What was the matter? 9. We have nice planets, right? Oh, that’s right Pluto was kicked off the list last year. My daughter will never know anything but 8 planets. I thought I’d look it up a little. Most people can say, “I remember when our solar system had 9 planets.” But, just when you think the solar system is getting simpler or smaller, terms like “dwarf planet” and “small solar system body” change the game.

To some it seems small, distant Pluto, the Roman god of the underworld (Greek Hades) dejected, slumps–only a rock. Actually, its demotion is more like a clarification. Since objects cross its orbit in the asteroid belt of Kuiper, and its mass is small, it is considered a dwarf planet by the International Astronomical Union who finally came to a consensus on celestial bodies. Its moon Charon keeps its moon status.

There are two other dwarf planets nearby. One is Ceres, found in 1801, our largest asteroid, inhabits some space between Mars and Jupiter in the big asteroid belt. In 2003, “2003 UB 313” was found beyond Neptune. This provisional name will be exchanged for a permanent one in a few months.

With the Hubble Telescope repairs, we should be able to locate dozens more dwarf planets near and beyond Pluto. Small solar system bodies are objects orbiting the sun that do not possess enough mass to have a spherical or near spherical shape. Hundreds of these will be found in the near future.

All this makes me think I really should look at the night sky more often. There’s a lot going on, on a whole different scale, and it puts things in perspective, once you start to take it in. Planet means “wanderer,” and it’s funny that even though we are on firm ground, really, we are planets too.

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