In The Field

AAS DPS 2008: Pluto

hal.jpg They’re still arguing the ‘is Pluto a planet’ question. I’ve got to be honest: without much of a stake in the debate (i.e., not being a PI to an icy planet that became a dwarf one) I can’t muster that much energy for it. But I’d still be scared of arguing with Hal Levison, who spoke earlier this weekend at a special session on the question.

Hal works at Southwest Research Institute in Colorado, and is an expert on solar system dynamics, and the processes by which little planetesimal pieces coagulate into bigger bodies. He’s a big body himself: burly, bearded and boom-voiced, dressed in baggy blue jeans and boots. Eyes flashing, he could be a viking without a helmet. He thinks the whole Pluto debate is kind of absurd. Just look at the distribution, he says. (A nice graphic that Hal refers to, courtesy Cassini scientist John Spencer, after the jump). In the graphic, which shows body size on the y-axis and orbital radius on the x-axis – in logarithmic scale – eight things clearly stand out. They are the planets. Everything else is part of a distribution: asteroids, trojans, KBOs, etc. It’s obvious.


If you go with a size definition, based on this roundness, his daughter will have to memorize 1,000 planets. He doesn’t like that. “Also, the mnemonic would really suck.” He wishes people wouldn’t associate non-planets with lesser scientific importance. He’s personally most interested in smallish Kuiper Belt Objects. “These guys,” he says, pointing to the small bodies, “including Pluto, are the coolest things in the solar system. I don’t care what people say.”

I’m glad the big guy is looking out for the little guy.

planets.png

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