Mirror Earth (13 page)

Still, when Seager went out to talk to potential employers, she got mixed feedback. “‘This will never happen,'” she would hear, “this” being transits. “That's what a lot of people said. When there was one transiting planet, and then an atmosphere detected through this method I had laid out, they'd say, ‘Oh, it's just one object, one method, one success.' And I said, ‘Look, we're going to have so many transits we won't know what to do with them.'” But since she was interested in planets many of the people she was talking to were in departments of Earth and planetary sciences. “They're used to holding things in their hands. Like drilling cores and things like that. And they just couldn't believe that it would ever happen.” Nowadays, she said, “you get exoplanet papers that are just … well, I hesitate to use the word
garbage
, but they're not always backed up with serious work. The attitude now is, ‘That's okay, if it's exoplanets it gets the stamp of approval.' ”

When Seager finally got a job offer at the Carnegie Institution of Washington, in Washington, D.C., some people strongly advised her against going, in part because she still had two years to go at the Institute for Advanced Study. “I asked John, ‘What should I do?' And he might have said, ‘You don't have any other offers, of course you should go.' But he thought about it for a while, and he just said, ‘Vera did all right.'” Bahcall was talking about Vera Rubin, an observational astronomer who began working in the late 1950s, when there were very few women in the field. Rubin was one of the first to show that galaxies rotated faster than they had any business
doing, suggesting that the gravity of some unseen matter was influencing their rotation. Many of her colleagues refused to believe her for years. Some even implied she was incompetent. But Rubin's observations eventually forced astronomers to accept the existence of dark matter, a mysterious, invisible, so-far-undetected material that outweighs ordinary stars by a factor of ten to one. It's gravity from the dark matter surrounding them that makes visible galaxies spin so fast. Today, Rubin is widely recognized as one of the most influential astrophysicists of her generation. Vera did indeed do all right.

At about the same time Dave Charbonneau and Sara Seager were blazing their way through Harvard's graduate program in astrophysics, two women were moving more quietly through a similar program on the other side of the country, at the University of California, Santa Cruz. Unlike their Canadian counterparts, neither Debra Fischer nor Natalie Batalha had started out studying cosmology. Neither had even been a hard-core physics geek in college—or in Batalha's case, at least, not when she started out. Her father worked in construction and her mother did accounting. They were convinced that their daughter would have the best shot at a good life if she majored in business, and she'd arrived at UC Berkeley in the late 1980s assuming that she'd do just that. Fischer was an even more unlikely astrophysicist: She'd gotten her undergraduate degree in nursing at the University of Iowa, and worked for several years afterward as a scrub nurse in open-heart surgery and in intensive care units.

Neither Batalha nor Fischer can say enough good things
about the other one. “Natalie is awesome. She is incredible!” Fischer exclaimed once when I mentioned her former office mate's name. “I love Debra!” Batalha said in a similar situation. I've never heard male astronomers talk quite like this. They might praise others' brilliance or technical skill or professional achievements, often with enthusiasm, but they rarely talk about what wonderful people their colleagues are. It would be an unfair stereotype to suggest that women in astronomy are warm and nurturing while men are all about nuts and bolts and pissing matches. But after nearly three decades of writing about astronomy, it's pretty clear to me that the entry of women into astrophysics in large numbers over that time has improved the overall empathy quotient in the field.

If they were unlikely to end up as grad students in astrophysics, Batalha and Fischer were even less likely to end up with such high profiles in the scientific community—Batalha, as Bill Borucki's deputy on the Kepler Mission and a frequent public spokesperson on the project, and Fischer, as a full professor of astronomy at Yale, where she was recruited a couple of years ago to bring some prestige to a department that had long been considered the poor relation of Harvard and Princeton. It's not that either woman's work in grad school was anything but outstanding; it's just that only a few graduate students of either gender, even at a top-rated program like the one at Santa Cruz, go on to be so prominent.

For Batalha, the first step into science came in her freshman year at Berkeley. “I didn't know from a young age that I wanted to study science at all,” she told me one afternoon in her office, right next door to Bill Borucki's at NASA's Ames
Research Center. “I wasn't the kid who read science fiction, I wasn't the kid who watched Carl Sagan's
Cosmos
, I wasn't any of that. And yet I grew up with an innate sense of wonder, I guess is the best way to describe it. And perhaps curiosity, or maybe an eye for the beautiful in nature. I guess that makes it sound a little bit simplistic.” Batalha did find the idea of human space exploration to be romantic. “Being an astronaut—of course, for every kid growing up at that time, it seemed like the most glamorous job ever. I mean all of us thought that.”

It wasn't until she took her first college physics course, though, that things began clicking into place. “Somehow,” she said, “the physics I learned in high school didn't inspire me. I think it's because it lacked the connection between mathematics and science that is so fundamental—being able to write down an expression that predicts what will happen in the future, and just putting the universe in an orderly context. I'm not a math buff by any means, but the beauty of it is what struck me.”

This revelation didn't turn Batalha into a scientist, but an internship she did the following summer at the Wyoming Infrared Observatory, near Laramie, arguably did. It was a pretty small-scale operation, which meant that a summer intern had a chance to do some actual research. Her supervisor was an astronomer named Gary Grasdalen, “a very brilliant man,” said Batalha. “He passed away quite young, shortly after I left.” Grasdalen gave her a problem to solve that had been stumping everyone. “It was just kind of a little technicality thing,” she said, “but I was able to solve it. And that surprised me. And it was fun. And the science that we got out of it as a result was very gratifying.” She decided to stick with astrophysics. “Gary told me that when I got back to Berkeley I should go knock on Gibor Basri's door.”

Natalie Batalha
(Courtesy of NASA)

At the time, Basri hadn't yet begun working directly on exoplanets, although he eventually would; his research concentrated on stars and on brown dwarfs—the objects Michel Mayor was originally interested in as well. But then, this was in the late eighties, when almost nobody was working on exoplanets.
“Geoff Marcy was actually kind of there at the time as well,” said Batalha. “He was a professor at San Francisco State, but he was going back and forth.” Everyone knew Marcy was searching for planets, but, said Batalha, “there was this kind of aura at Berkeley at that time that it was never going to go anywhere. Nobody took it seriously.”

Guided by Basri, Batalha majored in astrophysics, doing her undergraduate research on young, Sun-like stars. She then went on to Santa Cruz. Her thesis adviser there was Steve Vogt, who built the Hamilton Spectrograph at Lick Observatory, the instrument Geoff Marcy and Paul Butler would use to confirm Michel Mayor's discovery of 51 Peg b, and then use to discover their own planets. When the spectrograph was built, it had to go through a commissioning phase, running through a series of test observations to make sure it worked properly. Once it was fully operational, the only way to get access to the device was to apply for telescope time at Lick, but Vogt gave Batalha some of the data from the commissioning run to use in her thesis. “I ended up producing something,” she said, “and was invited to give a talk at a conference in Vienna.”

A week after the talk, there was another conference in Florence, Italy. Since she was already in Europe, and since it was relevant to her own research, Batalha decided to stay on. It turned out to be the meeting where Michel Mayor would announce the discovery of 51 Pegasi b. The title of the Florence gathering was “Cool Stars, Stellar Systems and the Sun”—and in fact, said Batalha, many of the people working in exoplanets today got their start studying stars. “The reason
for that is quite simple,” she said. “The way we find exoplanets is by observing changes in starlight.” This is true whether you're searching for radial-velocity wobbles or transits. “So you have to be a stellar spectroscopist, you have to be a stellar photometrist, you have to understand stellar activity and how it manifests itself on the surface of the stars. You have to have a deep understanding of all of it in order to pull out the exo-planet signal.”

As for Mayor's announcement itself, she recalled, she didn't realize at the time how important it was. Neither, as far as she could tell, did others in the room. “It was kind of nondescript,” she recalled. “We didn't really know what was happening, except there was a camera crew that came in to film it. So I knew it was something kind of important, but I didn't really pay too much attention. And Michel Mayor got up there and gave the talk, and I guess as a young student I didn't appreciate it so much. But there really wasn't a sense of excitement in the room. It just kind of passed. And I am sure there were people sitting there who did appreciate it, but there was no buzz. It didn't really sink in for people until later, the import of it.”

Batalha ended up taking a while to get through graduate school. She'd married one of Gibor Basri's postdocs, a Brazilian astronomer named Celso Batalha. “He was funded by the Brazilian government,” she said, “so he had to go back after his postdoc was over. All during this period, I was moving back and forth between Brazil and the U.S., taking leaves of absence. I actually spent my last year down in Brazil and wrote my thesis while I was there.” She stayed on in Brazil to do her own postdoc after finishing her Ph.D., still working on the
astrophysics of stars. While she was in Brazil, she got an e-mail from her old office mate Debra Fischer. “Debra said, ‘You know, there's this guy at Ames who's building a telescope at Lick to do transit photometry, and they really need help.' “

“This guy” was Bill Borucki. By this time, he'd been working actively on his planet-detection satellite for more than a decade. The first formal proposal had gone up to NASA headquarters in 1992 as part of the Discovery program. Discovery had been designed to accommodate relatively inexpensive missions—in the hundreds of millions of dollars rather than the billions—that would mostly focus on the solar system. According to Borucki, the thinking at NASA headquarters was, “We'll let people who are interested in other solar systems propose too.” So Borucki sent a proposal up in 1992. Back then, Kepler was known by the much klunkier name FRESIP, for FRequency of Earth-Size Inner Planets. NASA's response, in essence: It sounds like a great mission, but the detectors you'd need to pull it off don't exist.

So Borucki and his collaborators went back and built the detectors, and came back in 1994 with another proposal. “They looked at us,” Borucki told me, “and said, ‘This is a space telescope, like Hubble. Hubble cost several billion dollars. You think you can build this for three hundred million dollars?' They just threw the whole proposal out.” So he came back again in 1996. “We priced it three different ways, and showed how we could do it on the available budget. They said, ‘Okay, your price is plausible, but nobody has ever done photometry on thousands of stars at once, so your proposal is rejected. Go out and build an observatory and prove it can be done.'” By
now, Batalha's comment about Borucki starts to make sense: “Bill has this personality trait where negativity just rolls off of him. He doesn't accept it at all.”

So he and his crew went up to Lick Observatory on Mt. Hamilton, outside San Jose, where Geoff Marcy and Paul Butler had spent endless nights searching for wobbling stars. They took over a small, unused observatory building, fixed the place up, and put a telescope inside. Having been rejected so many times already, Borucki had a hard time convincing anyone at NASA to give him funding. “We had a charge card,” he said. “Everything had to be bought on a charge card. We'd buy this part, and that part—I shouldn't say that. You can't do that. It's illegal.” He was clearly not afraid, at this point, of getting in trouble.

“It was a great little telescope,” he said. “Visitors would come by and I'd tell them, ‘Here's the biggest telescope on the mountain.'” They'd look at him blankly, since it had only a four-inch light-gathering mirror—so small that even a half-serious amateur astronomer would sneer at it. The Shane telescope, a short distance away, had a mirror 120 inches across. But while Borucki's telescope couldn't gather a lot of light, its field of view—the amount of sky it could see all at once—was bigger than the Shane's. When you're trying to peer deep into the universe, a narrow field of view is what you want; it lets you get the most possible light out of just a few, very distant, faint objects. Borucki was less interested in the amount of light he could gather. He needed to measure variations in light, not total amounts, and he needed to do it for ten thousand stars at once. “So we did this,” he said. “We showed it could be done.”