Sara Seager's search for Earth-like planets

"Nature gave us so many planets we never anticipated originally," MIT physics professor and AAAS member Sara Seager told AAAS MemberCentral. Seager specializes in exoplanet atmospheres and interiors, with the goal of detecting an Earth-like planet with rocky ground and breathable atmosphere. (Photo: Justin Knight)

Sara Seager's office is located high above the Charles River in the tallest building on the Massachusetts Institute of Technology's Cambridge campus. Even on a gray and soggy day she boasts an impressive view. But Seager is usually too busy looking up to enjoy the scenery. 

"Everyone really just wants to know... Are we going to find planets that have life on them? That part is still far off, but we're getting closer and closer, and I think that is partly what has captured the public's interest," she said. 

Seager is speaking of the recent burst of interest in exoplanet research, or the search for planets that orbit stars other than our own sun. One way astronomers can detect them is when their orbits take them directly between their star and our telescopes- like the Kepler and Hubble space telescopes - which scan patches of sky to detect the slight dips in a star's brightness that could indicate a planet passing by. When a dip is detected the telescope takes a closer look. While it is sometimes easier to detect large planets, like Jupiter-style gas giants, the diversity of exoplanets has encouraged researchers like Seager to keep looking. 

"Nature gave us so many planets we never anticipated originally," Seager said. "There's planets that have a fraction of a day for their period. They are really hot,  hotter than hell." 

Seager currently works as the Ellen Swallow Richards Professor of Planetary Science and a physics professor at MIT. Along with distinguished company such as director James Cameron and astronaut Thomas D. Jones, Seager serves as an advisor to Planetary Resources Inc., a privately funded company that plans to develop the technology to mine asteroids.  

Seager was born in Toronto,  Ontario, and earned her bachelor's at the University of Toronto before moving to Cambridge to get her Ph.D. in Astronomy at Harvard in 1999. She specializes in exoplanet atmospheres and interiors, with the goal of detecting an Earth-like planet with rocky ground and breathable atmosphere. Since over 400 exoplanets have been discovered, including many rocky worlds, her goal seems achievable. In 2009 NASA launched the Kepler Spacecraft, the first satellite used exclusively for exoplanet research. Naturally, Seager is actively involved in the Kepler research. 

Once astronomers find exoplanets,  the next step toward determining if it is anything like earth is to measure its size, speed, and whether or not it has an atmosphere, which can be glimpsed when the light from a planet's home star passes through the gasses surrounding the planet.  

So far, the easiest atmospheres to detect belong to large, hot planets, something like a super-sized Jupiter. The light passing through their atmospheres gives off a spectrum of light that astronomers use to discover the chemical makeup of the atmospheres. Two planets in particular have yielded good quality spectra,  HD 189733b and HD 209458b. They are both hot Jupiters with tight, fast orbits of just a few days. HD 189733b was the first exoplanet to be discovered with carbon dioxide in its atmosphere, and Seager and her colleagues wrote a paper describing infrared light detected from HD 209458b. 

But exoplanets are not Seager's only interest. She recognizes the importance of mentorship for scientists of all levels, especially female students. While working as a postdoctoral fellow in Princeton, New Jersey, Seager met her mentor John Bahcall. She remembers him as the sort of mentor who encouraged his student's more outlandish ideas as long as they were based on solid physics and were achievable within their lifetime, and would subtly guide students towards good work habits. He "mentored without mentoring." 

"It's a massive insecurity that plagues all women. But it comes in such different forms with each person, that it takes a one-on-one special type of program to help them overcome these problems," she said. "Some people don't realize that its okay to think big and its okay to be phenomenal." 

Seager doesn't limit her support to her students, and she is not the only member of her family who looks upward. Her two sons keep her busy, especially after she introduced them to hiking. 

"One of the kids is seven years old now, and he's a super ambitious hiker," she said. "He only likes going straight up. I think this might be the year I can't keep up with him."