How I Killed Pluto and Why It Had It Coming - Mike Brown (2010)


In June of 2002, Chad Trujillo walked into my office and announced, “We just found something bigger than Pluto.” It turned out to be the second-best thing that happened to me that week, and it wasn’t even true.

Chad had recently moved from Hawaii to California to work with me on a brand-new project: using the 48-inch Schmidt Telescope at Palomar Observatory to find planets. Yes, the project sounds familiar, and yes, I had spent three years using exactly the same telescope to find exactly the same planets, and I had thoroughly failed to find anything. Yes, I had even been strongly advised by people who were concerned with my career and who had influence over whether I, a young assistant professor, stayed at Caltech or not, to quit this planet searching altogether and do something more respectable. But really, how could I just stop? Sure, we had looked at a lot of the sky—more than anyone else since Clyde Tombaugh had discovered Pluto seventy years earlier—but we hadn’t looked at the whole sky. So how do you know that you’ve done enough? If there is only one or two or even just three new planets out there waiting to be found, what are the chances that you just didn’t look in quite the right spot? And how could you really convince yourself that there was nothing there unless you looked in every single corner where things might be hiding? Maybe the whales really had just slipped through the net.

In the two years after I finally declared my initial search unsuccessful, every once in a while I would get a phone call or an e-mail from a friend who remembered that I had spent a long time talking about searching for planets, and the friend would invariably say something like “Hey, I just read in the newspaper that someone found a new planet, did you hear about it?” My breathing would stop while my pulse doubled as I tried to casually use my now-shaky fingers to quickly search my computer for the news of the day. “Oh, no, I haven’t heard, so, really, probably it’s nothing. Nothing at all.” At least I hoped. After all these years, the idea that someday someone would call me up and casually tell me that someone else had found a planet that I had missed still haunted me. Each time it happened, I would search the news and find, to the sudden restarting of my breath and calming of my pulse, that yes, indeed, a new planet had been found, but it was not a tenth planet orbiting around our sun, it was a planet orbiting a distant star far removed from our solar system. And I could then quickly tell the person how exciting it was that all of these new planets were being discovered around other stars and about how much we were learning, and how, oh, no, this was not the sort of planet I had been looking for at all. No one else was looking for planets out at the edge of our own solar system—at least that’s what I thought. What I hoped.

Though my first search had come to nothing scientifically, planets were still never far from my mind. I still wanted to find one. I just needed a new way to do it.

Less than a year after the first failure, I was back to work on the sky, and this time I was determined to do the job right. It was 2001, and though perhaps Arthur C. Clarke’s predictions of space tourism and obelisks on satellites of Jupiter had not come true, it was finally time to get rid of the hundred-year-old technology of the photographic plates. To some, it was a sad day when the photographic plate handling system at the 48-inch telescope was dismantled, though anyone who had ever had to work in the absolute darkness of the nighttime dome, moving plates from their holders to the telescope to the darkroom, could not have felt too bad to see it all go. The darkroom was turned into a storage room. The walls of the plate-handling room right next to the telescope were torn down to make room inside the dome. The mini elevator, which Jean had used innumerable times to transfer an exposed plate down to Kevin, who had been waiting in the darkroom, was permanently sealed. All of this was to make way for the new incarnation of the telescope: a modern, digital-camera-equipped, computer-controlled, remotely piloted sky-searching machine.

The difference between the digital camera and the old photographic plates was extreme. With the plates, you would walk upstairs, load the photographic plate, open the enormous shutter on the camera, and expose the film to the sky for about twenty minutes. It would take about ten minutes to unload the exposed plate and load in a new one and start all over again. In contrast, with the digital camera, you never had to walk up the stairs—indeed, you needn’t even be awake! The computer opened the shutter, exposing the digital camera for about sixty seconds, and sixty seconds later you could be looking somewhere else in the sky. It took two minutes for the computer to do what it had taken forty minutes for Jean or Kevin to do earlier.

The digital camera was small, though, compared to the photographic plates, and it covered only about one-twelfth as much of the sky (an area equivalent to about three full moons)—but since it was twenty times as fast, we were still ahead. Even better, in the 60 seconds that the digital camera was exposed to the sky it was able to see stars and moons and planets that were two or three times fainter than the faintest things we had seen on the photographic plates. I had been worried for the past several years that the things for which we were looking lurked just beyond the limits of what we could see. I had stared at many of those photographic plates that Kevin and Jean had taken, and had wondered what we were just barely missing.

But now we were in business. We could run almost every clear night of the year without worrying about overworking anyone other than the computer. We could see fainter things. We could cover more sky. In the first four months, we planned to redo the whole region of the sky that had taken us three years to complete earlier. And then we were going to keep going. Surely, all of this would lead us to the planet that was still out there waiting to be found. I was certain we would find it quickly.

I was so certain that we were going to be finding things immediately that I decided I needed help. I recruited Chad Trujillo, who was just finishing his doctoral thesis—on, conveniently, finding objects in the Kuiper belt—at the University of Hawaii. I wasn’t sure I was going to be able to convince him to come to Pasadena. He was so relaxed from his years in Hawaii that he seemed like someone more likely to live in a tree house than in a city, but having lived in the little cabin up in the woods in my earlier years in Pasadena, I knew where to find the most tree-houselike areas around. That, and the prospect of perhaps finding a planet or two, convinced him, and he moved to Pasadena and immediately set to work.

He knew what he was doing so well and was already so good at it that I essentially handed him the keys to the telescope and stepped out of his way. In a few short months, we’d finished looking at the area of the sky we had previously covered with photographic plates, and, to my great relief, there truly was nothing there to have been seen. Soon we were on to fresh sky. And somewhere in that fresh sky we made our first catch.

I’d love to write more about this very first discovery, about how Chad took pictures of the sky one night and then, while looking through them the next day, spotted a brand-new point of light slowly crawling across the images. I’d love to describe Chad’s excitement as he stepped across the hall into my office and showed me that first discovery. Yes, it was somewhat small—larger things had been stumbled upon in the Kuiper belt already—but we now knew for certain that if we could find this relatively small chunk of ice so quickly, any planets hiding out there were going to be within our grasp. I should have felt quite vindicated after all those years of searching. Perhaps I even did. The only problem is, I don’t remember any of it. When would it have happened? Probably November or December of 2001. Or was it January? Did Chad really come in and tell me? Did I then go across the hall and look at the pictures on his computer? It astounds me that I don’t remember any of it. I could go back and look up the records of that first discovery and perhaps refresh my memory. Instead, I went and looked back at my calendar for that time period to try to remember what else was going on that fall and winter.

My calendar is filled with Diane: trips with her to Hawaii, to the San Juan Islands, to the Sierra Nevada, trips on which I didn’t even check the phase of the moon before going. And when there weren’t trips, there were dinners and coffees and lunches. A year earlier I had worked from 10:00 a.m. until 10:00 p.m. most days of the week; but in 2001–02, for the first time since I had become an astronomer, I was actually leaving work at an almost normal time. I wasn’t even coming into work most weekends. I wonder if that first discovery came on a weekend when I wasn’t there, or when Diane and I were off for a week snowbound in the mountains. I like to think so. I was confident in the future Chad was working on; I was confident in the future I was working on, too.

The distraction of the winter continued into the distractions of the spring. By now Chad was discovering new objects beyond Neptune at a steady rate. One or two were big and bright enough that despite my distracted state at the time, I can still remember their discoveries—though, admittedly, a little vaguely. By the beginning of the summer, Diane and I had planned a long-weekend escape to a small beach town in the Yucatán. Before leaving, I had had a long conversation with one of my Ph.D. students. For some of my students I play multiple roles, including scientific adviser, speaking coach, writing instructor, tool provider, caffeine enabler, and, sometimes, relationship counselor. This student was complaining about the fact that her boyfriend, to whom she was engaged, thought that buying an engagement ring when they were not to be married for several years made no sense. On the airplane ride down to the Yucatán, I told Diane the story, and added the opinion that not only did I agree with the boyfriend, but that I thought engagement rings were a silly waste of money anyway and wouldn’t it be wiser to buy useful things? Like kayaks? Or bicycles? Didn’t she agree? No, she didn’t, actually.

I brought up the subject again at dinner our first night on the beach, and even once the next morning. Secretly, though, I had spent the previous month seeking out and buying the perfect engagement ring, and I had brought it with me. I had a plan. First, I would convince Diane that an engagement ring was the farthest thing from my mind; then I would plan a perfect seaside evening with dinner and a bottle of wine and spring it on her.

As I have since learned, I’m not very good at keeping burning secrets. Rather than waiting until the evening, sometime in the middle of our second day there, while sitting in a little hammock overlooking the water, relaxed and happy and talking about nothing in particular, I quickly went back to our room and came back out with the ring hidden in my pocket. I knelt. I proposed. I then went on for several verbal paragraphs about the symbolic importance of a ring as a combination of a public statement, something akin to earnest money, and a down payment on life. I then produced the ring. Diane was stunned silent. You could almost hear the machinery in her head reprocessing the last few days. Her first words, after a considerable pause, were: “You are such a shit.” She continued processing the days, the conversations about rings, the fact that she’d thought I was hopeless. She wanted to know when I had gotten the ring (on the street right outside the hotel, perhaps?), who else knew (my mother, of course), why it fit perfectly (I had surreptitiously tried on her rings, and they all fit perfectly on my pinky, which I then had measured), how I had managed to pick one she liked so much (I modeled it somewhat after her grandmother’s wedding band, to which I knew she was much attached). Finally I had to remind her that I had actually proposed and she had not, in fact, given me an answer. She looked up and said, “YES!”

•   •   •

The week back on campus was filled with people congratulating me. In the middle of the week, the chair of my department stuck his head in my office and invited me out for a walk. He had known Diane years longer than I had, so I was expecting some sort of congratulations followed by a lecture on how to treat her. “Congratulations,” he started, but surprised me instead with “you now have tenure.”

“Oh,” I remember saying. “Um. Thanks.”

“Thanks? Usually people are a bit more excited to hear this news.”

“Well, it’s only the second-most-exciting news of the week.”

Remarkably, receiving tenure at Caltech turned out to be only the third-most-exciting thing that happened that week. A day after my conversation with the chair of my department, Chad stuck his head in my office, looking no less relaxed than ever (perhaps having just come from surfing across town at Malibu), and said, “We just found something bigger than Pluto in the pictures from last night.”

Bigger than Pluto! This one I remember. Not as calm as Chad, I rushed across the hallway to see the pictures on the computer screen. The night before, the telescope had photographed an anonymous patch of the sky near the Milky Way galaxy, and there amid the thousands of stars was one tiny dot slowly inching across the sky. Chad had determined how far away it was (almost 50 percent farther from us than Pluto), and from that and from the brightness had guessed that the object was probably bigger than Pluto itself. It was certainly the largest new thing that anyone had found in the solar system for more than seventy years. This is what we had been hoping for. Only a dozen people in human history had ever discovered anything bigger going around the sun. It was the second-best thing that had happened to me that week.