How I Killed Pluto and Why It Had It Coming Read online

  How could this be? How could we have turned out to have been totally wrong? The answer, in a single word, is albedo. Albedo is a measure of how reflective something is. Freshly fallen snow has a high albedo, while coal or dirt has an albedo that is quite low. No one really knew what albedo to expect for things in the Kuiper belt, but back when the first object was found, everyone assumed that they were dark—as dark as coal or soot or ash. When we see an object out in the Kuiper belt, all we see is sunlight reflected from the surface. If that surface is dark and doesn’t reflect much light, the object needs to be big to reflect a lot of light, but if the surface is icy or shiny for some reason, it can reflect just as much sunlight while being smaller. It turned out that Object X was not as dark as coal or soot or ash; it was more like ice with a bit of coal or soot or ash thrown in. It was shinier than we’d initially guessed, meaning that it was smaller than we’d thought.

  I was disappointed at the time, but only a little. We were just getting started, and we had planets in our sights.

  Now that we finally knew how big it was—no planet for sure—it was time to give Object X a more dignified name. There are rules, decided upon by the International Astronomical Union, for the naming of most everything in the sky. Craters on Mercury have to be named for deceased poets; moon of Uranus are named for Shakespearean characters. For this type of object in the Kuiper belt, the rules said that the name had to be a creation deity in a mythology. After some quick thought, Chad and I decided that we should move from Old World mythologies, which have been traditionally used, to New World mythologies, in honor of where Object X was found. We even thought we might try to preserve the X. If you’re looking for New World mythologies and names that begin with X, you can do no better than the Aztecs. They were fond of X names—Xiuhtecuhtli is one of my favorites—but none of those felt quite right, or quite pronounceable. A little more Internet searching brought us to consider more local deities. Object X had been found at Mount Palomar, which is surrounded by Native American tribal reservations. Did the Pala tribe have deities? The Pechanga tribe? What gods did they worship in earlier days? We searched the Internet but couldn’t find any; our search brought up only early-eighties entertainers who were currently playing at their massive Harrah’s casinos, whose Las Vegas–style lighting is slowly ruining the view of the sky above the telescopes on top of Palomar. But we did find something even more local: The Tongva tribe, mostly known as the Gabrielino Indians because of their proximity to and assimilation into the San Gabriel Mission, had long been the inhabitants of the Los Angeles basin. In their mythology, the world was begun when their creation force—called Kwawar—sang and danced the universe into existence. It occurred to us, though, that there were actual members of the Tongva tribe around and that we really should ask their permission first.

  We didn’t know anyone in the Tongva tribe, but Chad went to www.tongva.com, found a phone number, and called it. The chief answered. Chad said something like, “Hi, I’m an astronomer from Caltech, and we just discovered something big in this region of space called the Kuiper belt and were hoping to name it after a Tongva creation myth and wanted to talk to you about it,” at which point the chief probably thought there was a pretty good chance that Chad was a lunatic rather than an astronomer from Caltech. Perhaps to hedge his bets, or perhaps just to get rid of Chad as quickly as possible, he gave the name of the tribal historian and chief dancer, who would be a better person to talk to about such matters.

  Chad made the next phone call. After Chad convinced the tribal historian that he was not a crazy person but was indeed an astronomer who had found something half the size of Pluto that needed a name, the Tongva agreed that Kwawar—or rather Quaoar, their preferred spelling—was the appropriate name.

  The correct pronunciation of Quaoar sounds like Kwa-o-ar, with a very soft W sound and a bit of a Spanish roll to the R, no doubt a product of the mission days. Simply saying Kwawar works fine, too. But when we picked the name, it didn’t occur to us that if you didn’t see it spelled Kwawar originally, as Chad and I had, the English language doesn’t give many clues on how to pronounce the word correctly. No word in the entire English language has that particular combination of four vowels: aoaa. People trying to pronounce it tend to start with the Q and then quickly trail off into nothingness.

  With a name in place, we were now ready to announce to the other scientists and to the world what we had found. A large international meeting of astronomers was taking place in Birmingham, Alabama, just two hours from my hometown, and we decided to make the announcement there. Chad submitted a paper with the innocuous-sounding title “Large Kuiper Belt Objects.” In his talk, he discussed everything that we had learned: Quaoar’s oddly circular yet inclined orbit, its diameter about half the size of Pluto’s, its icy surface. All of the questions, though, had nothing to do with Quaoar. Most of the inquiries from the press that day and over the following weeks never even mentioned Quaoar itself. They just wanted to know one thing: what did this discovery mean for whether or not Pluto was a planet?

  What, indeed? Even as more and more objects in the Kuiper belt were being found, Pluto still stood out as being significantly larger than any of the rest—but it was larger than Quaoar by only a factor of two. Was that enough to doom Pluto? In many ways, the answer was clearly yes. If after only nine months of looking, we could find something half the size of Pluto, how much longer would it take to find something the size of Pluto? We figured it was only a matter of months. For the confirmed Pluto fans, finding something smaller than Pluto meant nothing; Pluto was still the biggest, and thus they could go on calling it a planet. Yet it seemed that perhaps Pluto, while not yet dead, was on its deathbed. As The Birmingham News quoted me as saying later that day, Quaoar was a big icy nail in the coffin of Pluto as a planet.

  The week after we returned from Birmingham, Caltech threw a black-tie dinner to announce the kickoff of an ambitious fund-raising campaign. Many of the people at the dinner were donors who had been with Diane on one of her many Caltech travel-study trips around the world. Having just been in the newspapers a week earlier for the discovery of Quaoar, I was a minor celebrity at the party. Being engaged to Diane, though, made me a major celebrity.

  I spent the evening in a conversational loop: “You’re the person who discovered that thing out past Pluto?”

  Yes, indeed.

  “I want to introduce you to my friend—hey, do you know Mike Brown? He’s the guy who discovered the thing past Pluto.”

  “Sure, I know Mike; he’s the guy who is engaged to Diane Binney. Hey Mike, I want to introduce you to my friend—hey, do you know Mike Brown? He’s the guy who is engaged to Diane Binney.”

  “Sure, I know Mike Brown—he’s the guy who discovered that thing out past Pluto. Let me introduce you to a friend who is really interested in planets.…”

  Chapter Six

  THE END OF THE SOLAR SYSTEM

  Even today I spend much of my time exploring the outer edges of the solar system, looking for little worlds that have never before been seen, wondering what else is out there on the outskirts of our solar system. Someday I will have looked everywhere that the telescopes I have are capable of seeing, and then I guess I will have to declare that my days of exploring are finished.

  It will be nice to finally stop fretting every night when I see a few clouds in the sky as the sun goes down, or when the moon is nearing full and I know that the section of sky we wanted to cover this month is not quite done. It might be nice to wake up in the morning and see red-tinged cumulus clouds beautifully strewn across the L.A. basin and not have to wonder what we missed last night. And even though the computer does most of the hard work of looking at all of the data and finding the things that move, something always goes a bit wrong and I am always fixing a little bit of computer code or making slight improvements. The computer even sends me text messages on my cell phone when something goes really wrong. More often than not, it seems, trouble occurs on Saturday mornings wh
ile I am sitting drinking my coffee.

  Still, the fact that on any morning I might walk into my office and see something moving across the sky that no one has ever seen before, something bigger than anything found in perhaps a hundred years, adds an element of excitement to my life. I will be sad to be done, and what will I do after that?

  I did almost quit once, a little more than a year after the announcement of Quaoar. I thought, at the time, that we had reached the end of the solar system.

  Chad had moved back to Hawaii by then, eventually to marry, buy a house on the rainy, steamy, jungly northeast side of the Big Island, and work on telescopes. He and I (though, really, mostly he) had spent two long years staring at the sky night after night, and by the end of the two years we had covered 12 percent of the whole sky. While this might not seem like a huge amount, this time we really had covered a wide swath of the parts of the sky where we expected anything big to be. If we looked farther north or farther south, we would be looking away from the region where all of the planets are. The only things that we would find in the regions farther north and south would be things that went around the sun in orbits even more tilted than Pluto’s. The chances that something like that was out there seemed remote.

  I don’t mind taking bets on remote chances. Perhaps you could have said that our chances of finding something as big as Quaoar were remote, too, but there it was. The chances I would meet the person that I was going to marry in the basement of the 200-inch Hale Telescope were even more remote, but by now Diane and I had been married almost six months. Remote chances lead to good things, as far as I can tell.

  So in the fall of 2003, just as Chad was leaving and our two-year project to use the little telescope at Palomar to scan the skies for planets was ending, I began a new project about which I was quite excited. I was going to use the same telescope to scan the skies for planets. For the third time. This time, though, I wasn’t going to concentrate on the most probable places, I was going to concentrate on some of the least probable. The project was going to be even better than before, too, because other astronomers had become interested in using the telescope to look at vast areas of the sky for very rare quasars flickering at the edge of the universe, and they had built an even bigger camera—the biggest astronomical camera in the entire world!—to look at even bigger areas of the sky at once. This seemed, at least at first, like great news for us. We would sweep through the unsearched regions of sky faster than ever before.

  Right before Chad moved back to Hawaii, he modified all of the computer programs he had written over the previous three years so that they would work with this new supercamera. He automated everything as much as possible so that the project could continue in his absence. I was a little nervous about this, because it meant that I was stepping in to be the one in charge of the night-to-night workings of the project. I had been letting Chad take all of the major responsibility for years now, and in that time, I’d had many other projects going on to worry about and spend my time on. But things looked good. It looked as though with just a little bit of babysitting from me everything would run smoothly, the skies would be ours, and I could keep my day job.

  The new camera arrived about a month after Chad left, and it spent its first night taking pictures of the sky. At the end of the night, I set Chad’s computer programs to search once again for distant planets, for things that were moving in the sky. The computer worked all day long, as I carried on with all of the nonplanet-searching projects that were supposed to be occupying my time. Finally an automated e-mail informed me that the program was done. I opened up the file to see if the program had found anything. It had! Not only had it found things moving in the sky, it had found thirty-seven thousand of them!

  My heart sank.

  There could not possibly be thirty-seven thousand real moving objects in pictures from that night. In fact, I now know that there was precisely one.

  The computer was confused. But it was not Chad’s program that was the problem, it was the fancy new camera. To make the biggest astronomical camera in the entire world at a price that was not astronomical, the builders had had to compromise a bit on quality. One of those compromises had led to an incredible number of smeared spots, dark blemishes, light dots, black streaks, and bright blots showing up in each and every picture of the sky. The computer doesn’t do a good job of distinguishing between bright blots or light dots caused by the camera and those caused by something actually in the sky. Those thirty-seven thousand moving objects were almost all camera junk.

  I had not expected the computer or the camera to be perfect. I had anticipated that every morning I would have to look through some of the pictures to sort out the real objects from the fake ones. I had even taken the time to write a quick computer program to make this sorting extremely efficient; I could simply sit at my computer, press a single button, and a little postage-stamp-sized bit of the pictures from the previous night would appear on my screen. Three images would blink through in succession, and by eye, I would quickly be able to see what the computer had thought was moving. The eye is really good at finding the computer’s mistakes or verifying true finds. After some practice, I could look at perhaps as many as twenty different candidate objects in a minute. But to look at thirty-seven thousand would take me thirty hours straight for every one night’s worth of data. This was potentially a disaster.

  I sent an e-mail to David Rabinowitz, an astronomer at Yale University, describing the problems. David had helped build the new camera and had joined Chad and me as the third member of our planet search team; if anyone knew any clever solutions to the problem, it would be David. He quickly responded: There was nothing that could be done to fix the camera’s problem.

  The only plausible solution I could think of was to somehow make the computer program much, much smarter. But Chad was on to a new job and new responsibilities and couldn’t spend the next two years writing new computer programs the way he had for the previous camera. And even if he was working on this project, I couldn’t think of an obvious way to make the computer program smarter. Everything that I could think of doing to get rid of the thirty-seven thousand camera-junk objects had a chance of getting rid of the real objects, too.

  There was one solution: I could quit. Shut the project down. Declare an end to the solar system. In fact, it almost seemed like a good idea. Our chances of finding new objects were remote. The effort to find them was going to be extreme, if not impossible. If ever there was a time to cut our losses, now was it.

  I needed a second opinion. I walked up the road to my favorite café with Antonin Bouchez, one of my graduate students at the time and someone whose opinion I greatly trusted.

  “I’m done,” I told him. “We’ve looked at enough sky; if there was anything else out there, we would have seen it by now. The new camera is low quality, and I don’t think there is really any way to move forward.”

  I laid out all of my reasoning. I outlined the regions of the sky we had covered. I talked to him about the very slim probability of finding anything else. I showed him data on the new camera.

  “You’re crazy,” he said.

  “No no no,” I told him. I went through the arguments again. Look at the problems with the camera! Look at how well we’ve already done with the sky!

  “No, really, you’re crazy.”

  We drank more coffee. I described how I believed the solar system was laid out and why it now seemed clear that there was nothing larger than Pluto out there to be seen. And thirty-seven thousand moving things to look at in one night? Impossible!

  “Do you really believe there’s nothing else out there?” he asked.

  “I do,” I said.

  “So how are you going to feel when you pick up a newspaper one morning and read about someone discovering something right where you didn’t look?”

  I was reaching for the coffee again but stopped short. “Uhhhhhh. But it’s not going to happen since we’ve reached the end of the solar system.”

/>   “What if you’re wrong?”

  What, indeed? Ten years earlier almost no one had thought that there was anything to be found beyond Pluto at all and that anyone spending all of his time looking was crazy. Even just two years earlier almost no one had thought that something as big as Quaoar would be found and that anyone spending all of his time looking was crazy. I hadn’t bothered believing what most people thought back then, so why was I bothering to believe what most people thought now?

  “Do you really know there is nothing else out there?” Antonin asked again.

  Well. Okay. No. I really didn’t.

  “Then why exactly do you want to quit?”

  Because it was going to be hard work. Because I didn’t have help anymore. Because I wasn’t certain I’d be able to pull it off alone. Because I had been working on it for a couple of weeks and had hit what felt like insurmountable roadblocks.

  Looking back from a perspective of more than half a decade later, I think of this conversation as being as momentous as the moment when Diane walked through the door of the 200-inch Hale Telescope that first time that I saw her and my life irrevocably changed. A decade of floundering had ended that moment. This time the floundering had been for only a few months, but I had been floundering nonetheless. I can now even identify what the problem was, though I couldn’t have done so at the time. My biggest problem was not that the camera had specks or that the software was not up to the task. My biggest problem was that I had let myself become a normal person instead of an astronomer. I was believing what most people thought, because “most people” now included me.