Many of the readers of my previous blog might remember that I am a devout Pluto enthusiast. It is my favorite planet by far, and yes, i am including yours - what's it called? - oh, yeah, Earth.
I tried to not overreact when Pluto was demoted from planethood in 2005, partly because I felt then that the subject wasn't closed. Now the backlash over the International Astronomical Union's decision is growing in science circles.
Alan Boyle writes an MSNBC astronomy column called Cosmic Log and this week he printed the most significant salvo in this war of words I have seen this year. I'll reproduce a few key paragraphs but the entire article is fascinating and worth reading here.
The latest round in the planethood debate may well provoke planetary scientists into a revolt against the international body that usually has the last word on astronomical terminology, according to the top scientist for NASA’s mission to Pluto.
This week's announcement from the International Astronomical Union that Pluto and other dwarf planets on the solar system's edge would be known henceforth as "plutoids" has been seen by some as a sign of respect for what was once considered the smallest of the solar system's nine planets.
That's not how Alan Stern, principal investigator for NASA's New Horizons mission to Pluto, sees it. In fact, he wonders whether this will be the last straw for those who think IAU officials badly bungled their definition of a planet almost three years ago.
"They're almost needling the planetary community to go their own way," Stern told me today.
Stern isn't alone - and in fact, there's a wide range of opinions on the planethood question, ranging from outrage to acceptance of the IAU's definition. The main point of contention is the idea that a planet must have "cleared the neighborhood around its orbit" - a definition that Stern maintains could exclude worlds exactly like Earth.
In today's telephone interview, the former NASA associate administrator discussed Pluto, planethood and what planetary scientists might do about those questions. Here's an edited transcript of the Q&A:
Q: It's a case of defining a planet not by the thing itself, but by everything that's around it?
A: Exactly. I would like to see a definition that's really simple. I like to use the "Star Trek" Enterprise test. The Starship Enterprise shows up at a given body, they turn on the cameras on the bridge and they see it. Captain Kirk and Spock could look at it and they could say, "That's a star, that's a planet, that's a comet." They could tell the difference. They don't need a Ph.D.
In the case of the IAU, when Kirk asks, "Is it a planet?" Spock would have to say, "I don't know, Captain. We have to make a complete census of the solar system, feed that into a computer, and do numerical integrations to determine which objects have cleared their zone."
Q: So the issue of the nomenclature, whether it's a dwarf planet, or a plutino or a plutoid - as far as you're concerned, that's not the real point.
A: It's really about us "planetary scientists" having a basic understanding of the object after which our field is named. The reason we're having this discussion is because for a long time, we only knew of a few planets, and life was simple. Then, in the 1990s, there was this explosion in the variety of new kinds of bodies orbiting other stars and out in the solar system, because our technology got more sophisticated. We could suddenly see what we couldn't see before.
It's as if we were biologists trapped on a single desert island, and the only kinds of plants and animals that we knew were on that desert island. And then we were taken on a world tour of the flora and fauna of the earth. It would blow our minds. You would have two choices: You could say, 'Anything I didn't recognize from my own island is not living. I'm not counting that, because there would be too many varieties and I can't keep up with them.' Or you could say, 'I'm a scientist, and I have to adapt to new data. Wow, I really underestimated the situation.'
I think that's what's happened. But the IAU's reaction is, 'No, stop, I won't have any more planets. We have to limit the number because I'm more comfortable with a small number.' So you get this arbitrary algorithm that produces ridiculous results.
Q: Some of the discussion has focused on whether the approach to having an IAU that is the arbiter is not the right way to go nowadays. There's even talk about setting up an alternate organization.
A: That's right. Most things are done these days open-source and by consensus. You don't find little committees of 10 people speaking for 10,000, all without some sort of a sanity check. The fact that the IAU would claim that the world's astronomers have somehow met and decided something when it was a small committee of a dozen ... where were the experts in this field? What kind of process is that?
So people are asking, "What do we need these guys for? We'll set up an alternative." The IAU has no special claim. They have no police force or army. They're not the Supreme Court. If they're doing a bad job ...
The fundamental issue is that not many planetary scientists even belong to the IAU. The vast majority of its members work on galaxies, and stars, and black holes and cosmology. The reason most of the IAU doesn't care is because it's not their issue. The people who actually understand the physics, the chemistry, the work on planets aren't in the IAU. It's kind of like having a bunch of French professors deciding issues regarding the German language.
Q: So you think there eventually will be a consensus, which emerges not by taking a vote but by gathering more evidence?
A: I do. Let me give you an example: I think it's now widely expected among experts that we will find objects substantially larger than Pluto in the deep outer solar system, because now we really understand how easy planet formation was and how many kinds of things were thrown into the outer regions by the giant planets.
So just watch: When a Mars-size body of an Earth-sized body is found, it will be widely accepted that there will be a planet that doesn't fit the IAU's definition. At that point, even the last vestiges of the definition's defenders will say, "Wait a minute, we have to rethink this." ... The whole thing will be shown for the farce that it is.
Me again. Mr. Stern makes a great deal of sense to me and I appreciate that he communicates so well, in terms we lay people can understand. I am extremely eager to see what happens next on this question.
P.S. There have been hundreds of Pluto related pictures, products and gags flying around the internet in recent years. This one was new to me when blog reader Ryan sent it in recently. Thanks!!