How I Killed Pluto and Why It Had It Coming - Mike Brown [49]
Sedna remained Sedna. And with all of the crayon drawings showing Sedna’s rightful place in the solar system, Sedna was surely a planet, right? It’s true that I had argued against Quaoar and Pluto being planets on the basis of their being in the middle of swarms of similar objects. To me, it made no sense to pull one or even a few objects out of the swarm and call them something other than part of the swarm. But Sedna was, as far as we knew, all by itself. There was no swarm of objects out in the region of space where nothing was supposed to be found. Couldn’t it be called a planet? That, too, made no sense. Sedna would eventually be found to be part of a swarm, too. If we called Sedna a planet now, when that swarm was finally found, we would have to go through the process of planetary argument all over again. It seemed better to put Sedna in the right place to begin with.
Besides, Sedna was smaller than Pluto. In the beginning, we had been certain that Sedna would be bigger than Pluto. It was so bright! But when we finally got a chance to look at it with the Hubble Space Telescope, thinking we would get to see a little disk of a planet, all we saw was a tiny point of light, and that tiny point of light told us that Sedna was no more than about three-quarters the size of Pluto. How could that be? The answer is always the same: albedo. Sedna has an even more reflective surface than Quaoar, so part of the reason it is so bright is simply that reflectivity. Still, three-quarters the size of Pluto is big! No one else alive had ever found anything bigger in the solar system. But finding bright things that are almost certainly bigger than Pluto only to realize that, well, no, they aren’t actually bigger after all, gets old.
I hadn’t thought about it for a while, but it had been four years since my bet that someone would find something bright enough to be called a planet within five years. Much had happened since that bet. We had found Quaoar, at half the size of Pluto; Sedna out where the solar system was supposed to end; and dozens of other smaller objects that were nonetheless among the biggest things anyone else had ever seen. But we hadn’t found anything yet that would qualify for the bet to be won.
We announced the discovery of Sedna in February 2004. My bet ended on December 31. I had a little more than ten months to find something truly large, or I was going to lose.
I hate to lose.
And even worse than losing, I hate being stupid.
One thing nagged at me. I had almost missed Sedna. Sedna is so far away and therefore moves so slowly that the computer program I had written had almost ignored it. If Sedna had been just a little farther away and therefore moving just a little more slowly, we would never have found it. My computer program would have declared it to be a stationary star and kept searching. If Sedna was there and had been almost ignored, couldn’t there be something far out there that had been ignored? Finding such distant things would be crucial for testing my hypothesis about the birth of the sun and the odd population of distant objects that would have been created. But also, if we can see things that far away, they have to be big. It occurred to me that one of the best places to look for planets might not be in the remaining unexplored parts of the sky but in the many, many pictures I had already taken. If there was a planet already there that I had missed the first time around, I would, indeed, feel I had been stupid. But as I had learned earlier, the trick was not to figure out how not to be stupid, the trick was to be smart instead.
I spent most of that summer in my office slouched in front of my computer screen, writing, testing, and rewriting software. About halfway through the summer,