Two months shy of turning 40, the MIT astronomer Sara Seager decided to throw herself a highly unconventional birthday party. She rented a wood-paneled auditorium in the university’s Media Lab. She invited a few dozen colleagues, including an influential former astronaut and the director of the Space Telescope Science Institute. In lieu of presents, she asked 14 of her guests to respond to a challenge: help her plot a winning strategy to find another Earth, and do it within her lifetime.
“Hundreds or thousands of years from now, when people look back at our generation, they will remember us for being the first people who found the Earth-like worlds,” Seager began. She paced tightly, dressed all in black except for a long red-and-pink scarf, and spoke in her distinctive staccato voice into a hand-held microphone. “I’ve convened all of you here because we want to make an impact and we want to make that happen. We are on the verge of being those people, not individually but collectively.”
By the time of Seager’s birthday non-party on May 27, 2011, she figured that her life was “half over,” she told her audience. She had believed the discovery of other Earths was inevitable, but she now realized she would have to fight to make it happen. There was also an unspoken reason for her newfound sense of urgency: Her husband, Michael Wevrick, was gravely ill. With those thoughts in mind, she called her event “The Next 40 Years of Exoplanets,” videotaping and posting the talks online as a lasting astronomical manifesto.
So far, those next 40 years are off to a great start, at least from a planet-searching perspective. This past February, Kepler space telescope scientists announced the discovery of 715 new planets around other stars; the current total stands at 1,693. (In the 4,000 years from the emergence of Mesopotamian astronomy until the 1990s, scientists found a grand total of three new planets—two if you are a Grinch and don’t count Pluto.) There may be tens of billions of Earth-size worlds in our galaxy alone. NASA recently approved TESS, the Transiting Exoplanet Survey Satellite, to identify other worlds around the nearest stars. Seager has signed on as a project scientist. She is also working on an innovative way to bring small, rocky planets like our own directly into view.
Faint light from those worlds is trickling down on us right now. It contains the information about whether the cosmos is full of life: microbes, plants, perhaps even intelligent civilizations. “I have only one goal in life now, besides my kids,” she says, “and that is finding another Earth.”
If this is the part where you expect to hear about how Sara Seager always felt drawn to the stars, expect again. “You meet people now who say, I wanted to be a scientist since I was 5, I wanted to go to MIT since I was 6, but I was never like that,” she reflects. “It wasn’t on my radar.”
We are sitting in the atrium of the Gaylord National Resort, just outside Washington, D.C., at a meeting of the American Astronomical Society. It is 7:30 a.m. and Seager is fully focused, oblivious to the milling crowd of astronomers. “I knew I was different from other people from day one, I just didn’t know how the difference would manifest,” she says. “I spent more time daydreaming than anybody I know, and I was such a risk taker. I felt like I always had to live on the edge.”
Seager’s parents divorced when she was in elementary school. From then on she lived a divided life in her home city of Toronto: weekdays with her mother and stepfather, weekends and summers with her father. She had a difficult relationship with her stepfather and felt angry and abandoned. “I don’t know if I would be successful if I hadn’t been so beaten down. After that, I had a real lack of respect for all authority. And that actually was a very valuable trait, right?” she says. “It’s so liberating not to care about what other people are thinking.”
Her father, a physician who became an expert in hair transplants, instilled his own lessons on independence, telling Seager that she needed a career that would make her self-sufficient. He suggested medicine. But when Seager was 16 she attended an Astronomy Day open house at the University of Toronto’s St. George campus. She took a tour, picked up pamphlets and got hooked. “In retrospect it was one of the top ten days of my life,” she says. Her father was dubious of a career in astronomy. “He gave me a long, harsh lecture, ‘You can’t do that, you need a real job.’ But after that, every few months, he’d ask, ‘So what does a physicist do?’ He couldn’t get his head around the idea, what is their job?”
After an undergraduate degree in math and physics at the University of Toronto (where she worked with the same professor who had been handing out the pamphlets), she continued on to grad school in astronomy, coming under the guidance of Dimitar Sasselov at the Harvard-Smithsonian Center for Astrophysics. He directed her to an obscure but important problem in cosmology, modeling how radiation ricocheted off hot gas in the aftermath of the Big Bang. “Believe it or not,” she says, “that remains my most highly cited work.”
While Seager was focused on the edge of the universe, a quiet revolution was breaking out closer to home. In 1995, researchers found the first known planet orbiting another Sun-like star. Dubbed 51 Pegasi b, it was about as massive as Jupiter but circled so close to its star that it must have baked at a temperature of almost 2,000 degrees Fahrenheit. Over the following year, Geoff Marcy, an astronomer at the University of California, Berkeley, and his collaborator Paul Butler discovered six more exoplanets, three of which were also big and broiling. Humanity finally had hard proof that the universe is full of other solar systems, something that until then had been an act of Star Trek-style faith.
Sasselov realized the models he and Seager were applying to hot gas in the early universe could be used to study the hot gas in the atmospheres of these overcooked planets, if only someone could get a clear look at them. At the time, the known exoplanets had all been detected indirectly by their gravitational tug on their stars. Picture a black dog at nighttime, yanking on its owner’s leash. The only way you can tell the dog is there is by the owner’s herky-jerky movements.
Detecting starlight streaming through the air of an alien planet? Far more difficult. If it were possible, though, it could reveal all of a planet’s key details: temperature, composition, even the local weather.