An Astrophysicist in Search of E.T.
Sara Seager of MIT thinks we could be able to detect life on other planets in just 20 years
Sara Seager Bob O'Connor for The Wall Street Journal; Hair & Makeup by Bryan Lynde
Sara Seager, an astrophysicist at the Massachusetts Institute of Technology, is on the hunt for aliens. She thinks we might be able to find them within the next 20 years. In a new report in the journal Proceedings of the National Academy of Sciences, she argues that we may soon have the capability to detect life on other planets, a realization she calls "The Awakening."
She admits that she's excited. "Sometimes the anticipation of something rivals the actual discovery," she says in an energetic staccato in her office overlooking the Charles River in Cambridge. "Just the excitement that we can actually do it is phenomenal."
But she doesn't think we'll be chatting with extraterrestrials any time soon, and carefully qualifies her predictions. Those alien life-forms would need to be relatively close to our solar system, she says, and would need to fit particular criteria. "If there's some weird type of underground life, or if life is like a computer that doesn't give off a gas, we're not going to see it," she concedes. What we will detect, she says, with the help of improved telescopes and devices, is the gas that life as we know it emits.
Prof. Seager, 43, thinks there's something out there, "just by the sheer numbers of planets," she says. "Every astronomer knows that every star out there has at least one planet, and we have over 100 billion stars in the galaxy, and upward of hundreds of billions of galaxies in our universe."
The problem is that the bright light from the stars makes it nearly impossible to see the surrounding planets. (Earth, for example, is 10 billion times fainter than our sun.) That has made it difficult for even the Hubble Space Telescope, launched in 1990, and the Kepler spacecraft, launched in 2009, to find signs of life.
Prof. Seager is working with NASA to develop a "Starshade" to help block the light of stars so telescopes can better see exoplanets (planets outside our own solar system), which have become her specialty. The shade is a spherical disc with sharp points going around it, somewhat resembling a sunflower. She has a miniature, foot-long version of the 100-foot-diameter device, which is being designed to go up into space with a separate telescope at a total projected cost of $1 billion to $2 billion. The Starshade, which will have thrusters to move it into position, will help the telescope better see planets by blocking the light of nearby stars. Prof. Seager is leading a team that is studying how to start building it in 2017 for a 2023 launch. (See an animation of a starshade and a demo of how it will be deployed.)
Meanwhile, astronomers are looking forward to NASA's new James Webb Space Telescope, planned for a 2018 launch into space. It will be able to see infrared wavelengths, which is useful for detecting a wide variety of molecules. It will focus on stars that are smaller than our sun. "We haven't been able to find the true Earth twin yet because it's so very hard to find," says Prof. Seager. "It's like finding the proverbial needle in a haystack—first you'll find a bowling ball, then a ping pong ball and eventually figure out how to find the small thing." She expects the latest telescopes to get us closer to that goal.
"The James Webb Space Telescope will be a 'fast track' to very hopefully finding and identifying habitable worlds…. It will study super Earths—i.e. planets larger than Earth—going in front of small stars. I call this studying Earth's cousins instead of searching for Earth's twins. So the James Webb Space Telescope won't have to block out starlight but will actually use the starlight as an advantage: The starlight that shines through a planet's atmosphere can be measured such that the light that doesn't make it through tells us what gases are doing the absorbing in the planet's atmosphere. There is an MIT mission called TESS (Transiting Exoplanet Survey Satellite) to be launched in 2017 that will find the pool of transiting Earth-sized and super Earth planets that the James Webb Space Telescope will follow up [with] atmosphere study. In other words, TESS will discover and the James Webb Space Telescope will characterize. This is different from the Starshade and telescope system, or other similar mission concepts, that will do both the discovering and characterizing."
Where did you get your drive and motivation?
"My father was really hard on me. He really pushed me to accept this job, and I said, 'OK, it's the best I can do, to be tenured at MIT,'—which is really good the by the way—and he said, 'What? I never want you to be limited by your own internal thinking!' How many people have a parent like that? That's why I'm here and that's why I'm at the top of my field and I think big and carry it out—because he taught me how to do it…Things worked out really well for me. I think my dad would be really happy with where I am now."
For a planet to have life on it, the temperature can't be too hot or too cold. "I personally subscribe to the concept that some kind of liquid is needed—it doesn't need to be water—but you want a liquid so molecules can react and form other molecules," she says. If the molecules can't bond, she says, they can't give rise to life.
What might these extraterrestrial beings look like? Prof. Seager says she has imagined the possibilities just for fun, since we wouldn't be able to see exactly what any life we find looks like—whether it's a "slime world" or an intelligent species. Those planets would be so far away, she says, that we'll just be able to identify byproduct gases that point to the existence of living things. "If there are aliens looking back at us—we hope there are—they'll see our atmosphere has 20% oxygen by volume, and they'll know that oxygen is a highly reactive gas and shouldn't be there at all, and they may be able to imagine that there's life here," she says.
In turn, she has imagined what life would be like on different kinds of planets, such as one with a heavy atmosphere, where the density of air is similar to the density of water. "You can imagine some type of flying fish that can transition between water and air," she says. On a planet that has a dense atmosphere where light doesn't reach the ground, she pictures giant photosynthetic birds that have leaves as wings.
Born in Toronto, Prof. Seager first became interested in astronomy at age 5, when she peered out of a telescope at a star-viewing party. On camping trips as a child, she was amazed by the night sky. "There are so many stars that it's like they're going to fall on you," she says. When she told her father, a doctor, that she wanted to be an astronomer when she grew up, he disapproved. He was worried that it wouldn't be a financially stable career path and told her, "You have to be able to support yourself. You can't rely on any man," she remembers. But Prof. Seager wasn't deterred.
After high school, she went on to the University of Toronto, where she says she was good at math and physics but was "never the super-genius who always got the perfect score." She went on to Harvard University, where she earned a Ph.D. in astronomy in 1999. That is where she learned about the emerging field of exoplanets, a new, risky area because at the time, scientists didn't know whether exoplanets were really planets. Now scientists have confirmed close to 2,000 exoplanets, and they have thousands more candidates. Last year, Prof. Seager was awarded a MacArthur Foundation "genius grant" of $625,000 for her research.
She has been on the faculty at MIT since 2007. When she got the job, "my father was so proud because finally he thought I succeeded," she says. It was bittersweet timing, though. He died of cancer the year she got her job. She lives in the Boston area with her two sons, ages 9 and 11.
They already share her excitement about what scientists might find in space in the coming decades. Twenty years may sound like a long time to wait, she says, "but not considering the thousands of years we've been waiting."