The Smallest Lights in the Universe

by Sara Seager

  Concord is the home of Walden Pond, where Henry David Thoreau sat in his cabin and stared across the water, reflecting on the values of a well-lived life. One day, Mike and I stood together on the edge of that same body of water, the first hints of ice forming around its edges, a dusting of snow in the otherwise empty trees. The death of my father and the start of my academic career had coincided so closely, I couldn’t help feeling as though, from then on, there would be our lives before, and our lives after. I was looking over the edge of a precipice.

  CHAPTER 6

  The Law of Gravity

  A scientist’s greatest fear is missing something obvious. Not making a mistake, because in science, the greatest advances sometimes come from trial and error. The danger is in not recognizing the opportunity you have in front of you. In 2007, the National Research Council published a report titled The Limits of Organic Life in Planetary Systems. It contained a single line that has haunted me since the day I read it: “Nothing would be more tragic in the American exploration of space than to encounter alien life and fail to recognize it.”

  When we imagine life on other planets, we tend to imagine life as we know it. We see trees and birds and rain feeding into rivers. We imagine that we need to find a planet with oxygen in its atmosphere, because for us oxygen is the essence of life. But for half of Earth’s existence, there was no detectable oxygen in its atmosphere. For a long time, no oxygen was produced, and then the world absorbed whatever oxygen that bacteria pumped out until, after many tens of millions of years, molecule by molecule, a little oxygen managed to accumulate. On our planet alone, life has taken, and continues to take, so many different forms. Germs are life. Birds are life. Elephants are life. Imagine that there is a planet out there with dinosaurs still prowling across its surface, but we miss them because we’re too busy looking for little green humanoids. Even thinking of dinosaurs is too Earth-centric an approach. Maybe there’s a planet that’s only ocean, but that ocean is filled with schools of alien fish. Maybe there’s a supremely intelligent life-form that lives for millions of years. Maybe it’s become some kind of post-biological intelligence with hard drives embedded for better memories, and organs that self-replicate.

  That all might sound far-fetched, like science fiction, but space affords us almost endless possibilities. We can’t be intent on finding some version of us, or only some version of us. We might miss something different. Because we still can’t really see an Earth-like planet around a sun-like star, some in our community believe that we should try to find any planet that might have liquid water on its surface. Venus has no life on it because it’s too hot and its oceans have evaporated; Mars has no life because it’s too cold and its only water has frozen into ice. The relative heat that a planet receives from its star is an important dictator of its capacity to host life. So what if we expanded our search to include super-Earths—exoplanets with a mass larger than Earth’s but substantially smaller than ice giants—that orbit close to red dwarf stars, or stars that are smaller and cooler than the sun? They would be easier to see in nearly every way: They’re bigger than Earth and closer to their dimmer stars. Could somewhere like that sustain life?

  During my first days at MIT, I walked around campus and felt like I was inside a beehive. If I found a quiet spot, stood still, and closed my eyes, I could almost feel its collective energy rising through me. In one building, someone might be learning how to splice human genes. In that one over there, a new kind of robot would be taking its first tentative steps. New computers were being built. New materials were being engineered. Behind every door was another playground. It was a factory that turned imaginations into bigger imaginations. If clouds didn’t exist, someone at MIT would be inventing them.

  It felt like an entire city had been custom-built for someone like me. It wasn’t just the dreaming going on there that made me feel that way; it was the quality of the dreamers. I wouldn’t say there is an MIT “type,” exactly, because people there love so many different things. But I had spent my entire adult life among academics and scientists, at places dedicated to mining the most from their talents, and still I had never been surrounded by so many single-minded people, the best kind of obsessives. The objects of their affection couldn’t have been more varied, but the intensity of their affection burned at the same impossibly high temperatures. There would be no way to measure such a thing—if there were, someone at MIT would have figured out how—but I would guess that nowhere on Earth has a larger population of people who blink less. I’ve walked along the Charles River to get some air and seen dozens of people sitting on the benches that line the shore, together looking out at the water with the same unbroken gaze, seeing some crazy dream come to life in the wakes of sailboats. The rest of us will one day see their dreams come true. People at MIT build things, turning abstraction into practical magic. That’s what struck me most when I arrived: This was a place where I could make something, something miraculous that I could hold in my hands.

  I settled into my office in the Green Building. At twenty-one stories, it’s a landmark in Cambridge. My office is on the seventeenth floor. Today my desk is piled high with journals and stacks of research. There are shelves lined with books: Optics and Asteroids III and How to Build a Habitable Planet. A blackboard hangs on one of my walls, and it’s usually covered in scribbles. There are times when my office looks like a scene from A Beautiful Mind. Although I prefer chalk to grease pens, there are days when I blur the very fine line between advanced mathematics and abstract art.

  On that first morning, my office was still empty except for the light that poured through its long wall of windows. I took in my sweeping view of downtown Boston and the ever-changing angles of its shadows, and I remembered one of the last conversations I had with my father, when I told him that I’d finally decided to accept the job at MIT. “At my age, it’s the best I can do,” I had said. It was probably the best I could ever do, full stop. I would be starting at MIT with tenure at thirty-six and deep into a stable academic career, and life, at forty. Progress in increments.

  He glared at me. He might have been happy that I’d be taking the job, but he didn’t like how I was approaching it. “I never want to hear you say that something is the best you can do,” he said, surprising me with his passion. “I never want you to be limited by your own expectations.” It had been his last lecture.

  Sitting in my new office, I decided to think big, to try to make my brain like the universe, forever expanding. The whole point of tenure, after all, was to feel safe to pursue risky long shots. I affirmed the sense of purpose, the mission, that I’d spent my whole life searching for: I wanted to find another Earth, and then I wanted to find signs of life on it. That search had been considered most seriously under the Terrestrial Planet Finder mission, which was now on tragic, indefinite hold. Without it, I needed another way to see.

  Years earlier, an astronomer had suggested that we might be able to use a new piece of hardware, the in-development James Webb Space Telescope, to read the atmosphere of a transiting exoplanet just a bit bigger than Earth, orbiting a star just a bit smaller than the sun. A planet like that would also be rocky. Something like us.

  When I arrived in Cambridge, another fantastic new piece of space hardware was being developed: a telescope named Kepler—a new Hubble, a new Spitzer. It was the singular creation of Bill Borucki, a physicist who had embarked on an almost spiritual quest to build a space telescope designed to find transiting exoplanets. It was named for Johannes Kepler, the German mathematician and astronomer who became enraptured with space when, as a young boy, he saw the Great Comet of 1577. Bill wanted to give us that child’s fresh eyes, seeing for the first time new lights in the sky. I didn’t help get Kepler built, but I made a successful proposal to NASA to receive early access to its data, and I began counting down the days until its launch in March 2009, a little more than two years away.

  At MIT, something called the Tr
ansiting Exoplanet Survey Satellite, or TESS, was also in the dreaming phase. A third promising instrument. I was asked to take part in its development. Like Kepler, TESS would search for transiting exoplanets, but it would take aim at different targets. New ways to perform the Transit Technique were being developed all the time.

  The massive Kepler would look for Earth-size planets in Earth-like orbits around sun-like stars, thousands of light-years away. Unfortunately, its discoveries would be too far away for meaningful follow-up, for us to know if those Earth-size planets were also Earth-like. The smaller TESS would search around closer stars instead, favoring red dwarf stars that are “only” tens or hundreds of light-years distant. Because those planets would be nearer to us than anything Kepler might find, and because red dwarf stars are smaller than the sun, perhaps we would be able to monitor them with our next generation of telescopes to study planet atmospheres for signs of life. In other words, Kepler would give us potentially thousands of small worlds, helping to determine how common our potential doppelgängers are. If TESS became a real mission, its exoplanet haul would reveal fewer Earth-size planets, dozens at most, but it would give us greater odds of recognizing a rocky cousin with the potential for water rippling across its surface—and whoever might call it home.

  I closed my eyes and tried to imagine what it would be like to live on such a different world. For an exoplanet orbiting a red dwarf star to receive enough heat to sustain life, it would have to be so close that it wouldn’t spin on its axis nearly as quickly as Earth. It would be “tidally locked” like the moon, with one face forced to look always at its star, bathed in perpetual light, and the other always cast in darkness. With a star so huge in the sky, maybe the best place to live wouldn’t be where it’s always daytime. The planet’s proximity to its star would mean bombardment with intense ultraviolet radiation and frequent, powerful stellar flares. Maybe, for alien astronomers, the best place to live would be where it’s always night. Or maybe it would be somewhere along the line between the light and the dark, where it’s always sunrise or sunset.

  None of that seemed hospitable to me, at least within our species’ narrow definition of “home.” I understood why our community was investing in finding habitable planets around red dwarfs, but I wondered whether my fellow astronomers were looking at those planets only because it was easier, not because they might actually find something—like a person searching for her lost keys under a streetlight because that’s the only place she can see. Deep down, I didn’t want an approximation of Earth. I wanted to find an equal, better than the best.

  Even with James Webb and Kepler on the horizon and TESS in our dreams, I couldn’t shake the feeling that we were going to miss something. With my father’s voice echoing in my head, I found myself thinking constantly about signs of life. I always came back to atmospheres, to gases, to the air that we, and someone or something else, might breathe. I reminded myself that alien air wouldn’t necessarily look or taste or smell anything like our own. To find it, maybe we’d have to develop new senses.

  * * *

  ●

  My work verged on all-consuming. I felt a constant internal pressure to perform—to be the first, to be the best. I received accolades for my efforts. I won the American Astronomical Society’s Helen B. Warner Prize for accomplished young astronomers not long after I arrived at MIT. (I was the first woman to be awarded it in more than fifty years, even though it was named for one.)

  Mike received far less recognition for his supporting role. Nobody gives you prizes for getting your kids to school on time, or for making sure there are always diapers on hand. Whenever I took a moment to look down instead of up, my divided focus found Max and Alex. The boys weren’t old enough to take with us on adventures, and they were still too young to leave for long stretches with somebody else. At work, I was a star. At home, only a whisper below the idyllic surface of things, Mike and I had begun a slow drift apart, as though Mars had released its hold on its two moons. We both knew it. That kind of divide can sneak up on you, but once it’s there its existence is hard to deny.

  Mike blamed me, mostly. He said that he was the same person he always had been. He still liked to put a canoe on the roof of his car and find a foamy spring river to run. I was the one who had changed. Mike just wanted his canoe partner back, the person who spent her winters with him planning our next adventure and her summers in the same boat. Now, more often than not, he did the dreaming and doing alone.

  My immediate answer was to hire help. Not long after we had settled in Concord, I scoured the online classifieds and saw one that stopped me with its sweetness: Hi, my name is Jessica, and I’m 17 years old. I am a high school student in Waltham. I love kids, and…She was looking for work after school. The boys immediately fell in love with Jessica. She was great with them, a warm bundle of energy, and I thought Mike would appreciate the lightening of his load. I’m sure he did, but it wasn’t just more time that Mike wanted. He wanted more time with me.

  I couldn’t see a remedy. I never felt like I had enough hours in the day. Money was tight, too. Years earlier, I had set my sights on a new white-water canoe—a beautiful Dagger Rival. We had more boats than just Mike’s Old Town Tripper by then, but I had become infatuated with the Dagger Rival. I looked for a used model with no luck, so I splurged on a new one, painted teal, its hull clear of even the faintest scratch.

  Mike told me that it was a dumb boat, too big and flat for us. It was built for novice paddlers, he said, not for expert white-water canoeists. But only one of us was an expert anymore. He paddled most weekends; I joined him less and less, until eventually it was rare that I did. I had grown out of wanting to be cold and wet all the time, and someone had to look after the boys. There were springs when Mike and I hardly saw each other. I worked long hours during the week, caught up in the end-of-term rush, and he was gone on the weekends, chasing the melt, often in my Dagger Rival. We both had our passions. Unfortunately, as with too many married couples, the person with whom we had pledged to share our lives was no longer principal among them. It could feel as though we were misapplying our love.

  There is a phase of your life when you’re building toward something, when your entire existence can feel like a construction project, a to-do list that you’ll spend years crossing off. Young kids, ascendant career. The universe is so enormous. But one day we’d be finished with our respective searches and we could find each other again. “We’ll have time someday,” I told Mike. “We’ll have money someday. We’ll have time and money someday.”

  I meant it, too. I meant it like a promise. Mike and I settled into an uneasy peace, pretending that the promise was enough.

  * * *

  ●

  Kepler was ready for launch in March 2009. Mike and I went down to Cocoa Beach, Florida, just south of Cape Canaveral. We brought along Max and Alex. I had some meetings to attend, but we made a vacation around them. We stayed in a hotel on the ocean with other space families. While the boys played in the water, I looked up the coast and thought I could see Kepler’s Delta II rocket on the pad, shining like some distant skyscraper. It was hard for me to believe it was real.

  The launch was scheduled for late at night. I found a babysitter for the boys. She came to our hotel, and she watched closely as I brushed their teeth after they were tucked into bed, using just a little bit of toothpaste so they wouldn’t have to spit it out. She thought that was some trick, and I smiled at her apparent awe. I was about to watch a rocket launch a telescope into deep space, with which we might find thousands of new planets, but I agreed—brushing teeth in bed was a kind of miracle, too.

  Mike and I headed for the Kennedy Space Center, where we waited in the Rocket Garden with hundreds of others, mostly scientists and engineers, a few of them with proud and buzzing families. The skies were clear but it was a little windy, the gusts blowing in the wrong direction. Instead of being able to watch the launch f
rom the bleachers set up three miles from the pad, we were bused to a different viewing area, five miles away. I spotted Bill Borucki with his children and grandchildren, so near the end of one journey and the beginning of another. The rocket was bathed in spotlights, and it was all any of us could see. Even from our distance, it looked made of polished stone. It looked to me like a sculpture, like a monument to everything good.

  We heard NASA’s mission control over loudspeakers, making their way through their final system checks. We heard the word “nominal” again and again. At NASA, that’s the word you most want to hear. Nominal means go. The rocket was a go for launch.

  Bill and his colleagues had put decades of energy and effort, not to mention hundreds of millions of dollars, into Kepler. Now they risked being consumed by nerves and that ill-timed wind. Not long before, a different NASA mission had suffered a catastrophic failure, and a new satellite had plummeted into the Indian Ocean. There isn’t a lot of middle ground with rockets. Every launch is all-or-nothing: Rockets either go to space or explode trying.

  This rocket’s engines sparked to life. Light covers five miles a lot faster than sound, and for an anxious second or two, there was only a bright, silent burst. Then a low rumble made its way through the swamps and into the balls of our feet. Our ears filled with the noise that fire makes. The rocket lifted off the pad, slowly at first, picking up speed as it climbed higher and higher, out of gravity’s clawing reach. The solid rocket boosters detached on schedule, and we saw them glow red hot as they started their long fall back to Earth.