Pluto, god of underworld, gets busted down to demigod
It’s old news now, but I haven’t had a chance to comment on this monumental change in our solar system’s family tree. The International Astronomical Union (IAU) this month demoted Pluto from planet to dwarf planet, supposedly removing it from the pantheon of bodies called planets.
I told my students I’m thinking of holding a wake in Pluto’s honor. Of course, it would just be an excuse to have a party. I’m not really all that upset. Science, after all, is all about change.
And what a tiny change, at that.
Here are the facts. Way back in the early part of the 20th century, Percival Lowell, who had some pretty odd ideas about the solar system and a lot of other things, insisted on the basis of those odd ideas that there had to be a ninth planet outside the orbit of Neptune, the so-called Planet X which fringers still talk about.
After Lowell died, Clyde Tombaugh in 1930, using a blink comparator, discovered a tiny speck on his photographic plates that was eventually identified as a new planet. (Tombaugh discovered 14 other tiny specks this way, all of them asteroids.) It was quite an achievement, given the tiny size and immense distance of Pluto from Earth, and its snail-like movement across the heavens.
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