The Life in Our Stars
One spring day in 2011, Sara Seager, an MIT professor of planetary science and physics, invited 14 of the world’s most influential astronomers to a birthday party of sorts. In an auditorium at the glistening MIT Media Lab in Cambridge, Seager stood before her distinguished guests, including Harvard’s Dimitar Sasselov, David Charbonneau, and Lisa Kaltenegger, and Berkeley’s Geoff Marcy, dressed entirely in black, a hue that matched her raven hair and dark eyes. The only dashes of color were her red-and-pink scarf, red lipstick, and scarlet fingernails.
In lieu of presents, Seager challenged her guests to bring her a new world. And not simply any world, but a planet just like ours, what scientists like Seager call an Earth twin—a small, rocky planet with liquid oceans and an oxygen-rich atmosphere, orbiting its sun at a comfortable, Earthlike distance. As recently as 25 years ago, this ambition would have been considered the stuff of science fiction. Back then, the idea that there were any planets beyond our solar system was merely theoretical; no one had ever seen one. Our observational powers were limited to the universe’s brightest lights: its stars. A planet located beyond our solar system—what’s known as an exoplanet—would be so dark as to be invisible. Yet as astronomers gazed into the universe, they were constantly haunted by the odds—with all those billions of stars, there were bound to be more planetary systems out there. We just didn’t know how to find them.
And yet just two decades later, we now seem to be on the brink of answering one of mankind’s greatest questions: Are we alone? Scientists like Seager are convinced that we will find signs of an Earthlike planet—soon. “I believe that in our lifetime,” Seager said during a Cambridge TEDx conference in 2013, “we will be able to take children to a dark sky. And point to a star and say, That star has a planet with signs of life in its atmosphere. That star has a planet like Earth.”
When that discovery is made, it will almost certainly involve a group of scientists who work in the Greater Boston area. In fact, the astonishing progress made in what we know about other planets in the universe can be traced largely to this pioneering group. Though they don’t have the world’s biggest telescopes or the most advanced equipment, these Cambridge scientists—among them Harvard’s David Latham, 74, and David Charbonneau, 40; and MIT’s Seager, 43—make up one of the highest concentrations of exoplanet experts in the world. And they reached the vanguard of the field by repeatedly defying prevailing scientific wisdom: They pursued seemingly outrageous theories, painstakingly chasing the unknown. Their story is a tale of brave thinking, impossible odds, and relentless optimism.
Last November, I went to see Seager at her Kendall Square office, which overlooks the Charles River. Though she was technically on sabbatical, that very morning she’d been in New York City with a team of people she’s leading— including scientists from NASA and the Jet Propulsion Laboratory—who are working on a giant gadget that should help our space telescopes see distant planets more clearly. (It’s a star shade—essentially a huge flower-shaped umbrella with very precise notches where the petals join—that’s designed to unfold in outer space and block the glare from a distant star, allowing scientists to see orbiting exoplanets.) A few days after our conversation, she would meet with fellow MIT and Harvard astronomers working on the next exoplanet-hunting satellite, which will scan the entire sky to find potential new Earths for telescopes in space and on the ground to study. And in a couple of weeks, she’d be off to NASA’s Jet Propulsion Laboratory, in Pasadena, California, to hear updates from a former student who is developing a small exoplanet-hunting “nanosatellite,” which could be launched on the cheap and in a hurry.
At that birthday conference four years ago, Seager had pronounced her own life “half over,” and told her audience she believed that her generation of researchers was destined to leave a legacy that would be celebrated thousands of years from now, when human beings might set sail across the final frontier. “Hundreds of thousands of years from now, when people look back on our generation, they will remember us for being the first people who found the Earthlike worlds,” she said. “We are on the verge of being those people.”
Now, as we spoke in her office, Seager unpacked a brown-bagged soup and salad and apologized for eating lunch as she talked. Answering the question of whether we’re alone seems tantalizingly close, she said, hence the urgency in her voice. This moment is “the first time we have the capability to find life,” she said. “It’s within reach.”
In the beginning, we listened.
In September 1959, two Cornell physicists published a paper in Nature suggesting the best radio frequency for transmitting interstellar messages. If aliens were out there and trying to communicate, the thinking went, we’d hear them—if we just put up the right antennae. Thus began the official search for extraterrestrial intelligence (SETI). “The probability of success is difficult to estimate,” the scientists concluded, “but if we never search, the chance of success is zero.”
Over the next two decades, increasingly sensitive listening posts were built around the country, and by the late 1970s, SETI researchers even convinced NASA to back some of their efforts. But year after year, decade after decade, the aliens refused to oblige them. Meanwhile, our own solar system proved to be excessively harsh: Satellites and telescopes, lunar landers, and Mars flybys turned up only dead rocks, poisonous atmospheres, and dust—along with incinerating heat and blood-freezing cold. In the mind-boggling vastness of space, it seemed there was nothing remotely like life to keep our collective psyches company.
Eventually, Congress began to treat the search for extraterrestrial life as a grand folly. In 1992, NASA earmarked $100 million over 10 years to search the 1,000 nearest Sunlike stars—but the very next year, Senator Richard Bryan, a Democrat from Nevada, helped kill the funding, then danced on its grave. “The great Martian chase,” he said, “may finally come to an end.” He was right. From then on, NASA stayed away from the search for extraterrestrial life, and most astronomers followed suit. Instead, serious astronomers focused on solving other mysteries: how the universe was born, how it evolved, where it was headed.