Mirror Earth (14 page)

The telescope was named Vulcan. “No”—Batalha would say a decade later, seeing my eyebrows go up—“it had nothing to do with
Star Trek.
” Vulcan was a hypothetical planet orbiting between Mercury and the Sun. The French mathematician Urbain Le Verrier proposed its existence in 1859. This wasn't the first time Le Verrier made such a prediction. In 1846, he suggested that irregularities in the orbit of Uranus could be explained by the gravity of an unseen planet. He told observers where to look for it. When they looked, there was Neptune. Mercury also had an odd orbit, so Le Verrier invented Vulcan, named for the Roman god of fire. Things didn't work out so well this time. Despite extensive searches, Vulcan was never found. It turns out that the irregularities in Mercury's orbit come from a different source. The tiny planet is so close to the powerful gravitational field of the Sun that Newton's version of gravity, which is normally sufficient to describe planetary orbits, doesn't work. You need Einstein's general relativity to explain it, and that theory wouldn't be published until 1916.

Still, it was a good name for a planet-hunting telescope. When Debra Fischer first told Natalie Batalha about the Vulcan telescope, Batalha noted it with no more than mild interest. But over the next year or so, she said, “it cogitated in my brain,” and, after about a year of cogitation, she e-mailed Bill Borucki. Her special area of expertise in stellar astrophysics was starspots—sunspots on stars. “I said, ‘You know, I'm really interested in how you can disentangle a transit signature from spot signature.” It's a good question: If you see a tiny, repeating, regular dip in starlight, how do you know it's a
planet moving in front of the star and not a dark starspot on the surface, rotating along with the star? “As luck would have it,” she told me, “or maybe
luck
isn't quite the right word, that was one of the weaknesses in an earlier Kepler proposal. Ed Weiler at NASA headquarters, whose specialty is magnetic activity in stars, had expressed doubt about Kepler's ability to disentangle these two signals, and so I proposed to Bill that I come think about this problem. And he invited me to come, and I came in February of 2000.”

In part, she came because she was following the money. NASA was getting more and more interested in exoplanet searches during the late 1990s; it was clearly something the public was interested in, and the public ultimately paid the bills. The agency had honed its public relations machinery during the 1960s, when it successfully painted the race to land men on the Moon as a grand adventure for humanity and a quest for scientific knowledge. In the 1990s, NASA's PR apparatus was geared up once again, this time to tout the International Space Station. Just as with the Moon landings, this project was a geopolitical maneuver. Its real function was to keep Russian rocketeers usefully employed after the downfall of the Soviet Union, so they wouldn't be tempted to sell their expertise to Iran and other dangerous clients. What the public mostly heard, however, was that it was a major step forward to living and working in space, and an orbiting platform for amazing science.

In fact, the space station has turned out to be a lousy platform for science, as scientists had said all along that it would be. But the agency did do spectacular science, with the Hubble
Space Telescope, the Spitzer Space Telescope, and other orbiting observatories; with its probes to Mars, Jupiter, Saturn, and other planets; and with satellites such as COBE and WMAP, which tuned in to the ancient light from the Big Bang. As Bill Borucki and Geoff Marcy knew all too well, the agency had also been interested in planet-hunting for decades. It had even funded a number of studies, but had always concluded that a search for extrasolar worlds would have to wait for advances in technology.

In 1995 and 1996, however, Michel Mayor and Geoff Marcy had shown that we didn't have to wait after all. NASA officials quickly realized that the American public—their ultimate bosses—were captivated by the search for planets and for life. So the agency scrambled to repackage several of its existing projects, including its planned “Next Generation Space Telescope,” into a program titled Origins. In January 1996, at the same meeting where Geoff Marcy stood up to announce his first two exoplanets, NASA administrator Daniel Goldin gave a talk about the Origins idea. It wasn't just a space-based program, he said. Origins would also include research on the origin of life on Earth, for example, and on the range of environments in which life could conceivably survive. And it would include ground-based searches for exoplanets. When Geoff Marcy went to the Keck II telescope a month or two after the conference to look for planet wobbles with the world's most powerful telescope, he used telescope time NASA had purchased from the Keck Observatory.

NASA's newfound commitment to funding planet searches and related research had also made a big difference to Bill
Borucki's Kepler project. “We'd been pushing this mission before people had found planets,” he told me. “When they found planets, that helped our proposal.” The Vulcan telescope on Mt. Hamilton had proven that Borucki and his collaborators could successfully monitor the brightness of tens of thousands of stars at once, and he'd gone back to NASA again in 1998 to propose Kepler. This was now the third time. “They said, ‘That's just great that you can do that,'” Borucki recalled, “‘but nobody has ever built a system that could maintain the required precision in orbit.'” What they meant was that the spacecraft has to rotate in order to keep its gaze focused precisely on its target stars. You do that with reaction wheels: The wheels turn in one direction and the spacecraft responds by turning in the other direction. But, he said, “reaction wheels aren't perfectly round, okay? Plato is the only one who believed in perfect circles, and he died a long time ago. Ours aren't Platonic wheels, they're real, and they shake, and so the satellite will shake, and the stars are moving across your pixels.”

“So, of course, they rejected the proposal,” he said. Again. NASA told him to go into the lab and build a test facility that proved it could be done. This time, at least, Borucki didn't need to use his credit card to build the test facility. “They gave us five hundred thousand dollars. That's nowhere near enough money, but Ames lent us another five hundred thousand dollars. Which was sort of scary because you have to pay five hundred thousand back. But it was progress.” That funding made it possible for Natalie Batalha to join the project. But it wasn't just about following the money for her. “It's more than
that,” she said. “For me, this is such a profound quest. It's exploration in the very fundamental source of the word, right? Human beings have that seed in them to always search for new horizons—humanity in general, not just scientists. I think about that a lot. It drives me and it motivates me, and it makes me particularly interested in this area. And for me just as a career in general, I couldn't do anything that didn't have some kind of profounder meaning. Perhaps scientists all have that in common as well. I don't know.”

Natalie Batalha decided to become an astrophysicist after she took a freshman physics class and spent a summer at an observatory in Wyoming. For her old office mate Debra Fischer, it didn't happen until she was in her late twenties; astrophysics was her second career. “I don't like to tell anyone about the earlier part of my life,” she told me in her office at Yale. “It's just—I don't know why, because now it shouldn't matter. I'm tenured at Yale, what difference does it make? But I got my first degree in nursing, it turns out.” This may not sound like such a terrible thing, but it's possible, although at this point in her career highly unlikely, that some of her colleagues would take it as showing a lack of seriousness. Even Carl Sagan, an astrophysicist and a professor at Cornell, was looked at suspiciously, and even denied admission to the National Academy of Sciences, because he also wrote popular books, appeared frequently on
The Tonight Show
, and hosted the
Cosmos
series on PBS.

After Fischer got a degree in nursing at Iowa, she wound up at the hospital at Case Western Reserve University in Cleveland, Ohio. “The whole time,” she said, “I was much more
fascinated with the instruments and the way things worked, the defibrillators and everything, and less focused on the poor sick people, actually.” Even so, she was so immersed in the world of health care that when she decided to take her next career step, the plan was to go to medical school. Her boyfriend at the time—now her husband—was a medical student at Case; when he went out to San Diego for his residency in internal medicine, Fischer enrolled at San Diego State University to fulfill her premed requirements. “It was kind of a luxury,” she said, “to go back to school and know that I could sort of play around a little bit. I had time to take a course on the history of jazz or classical music or art history.” She'd always loved mathematics, so she also took some math and physics and, just for fun, an astronomy class. “I realized that astronomy was this amazing study of everything,” she said, “with the insignificant exception of Earth. If you look at Earth compared to the universe it's nothing. It seemed so exciting.”

By the time her husband moved on to a second residency, in cardiology, in San Francisco, Fischer had given up on medical school. She enrolled at San Francisco State University to do a master's in physics. “They had just hired Geoff Marcy—I think it was 1984 or something like that. I went observing with him at Lick,” she said, “and just fell in love with the whole observatory and the process of looking out into the universe. It was a great opportunity.” The obvious next step was to apply to a Ph.D. program, but Fischer wasn't so sure. “I thought, ‘I'm too old, I'm already thirty, I shouldn't go back to school.'” So she taught some undergraduate physics courses at San Francisco State for a couple of years, but, she said, “I couldn't
stop thinking about going back.” She applied to several schools without a huge amount of confidence. “I remember Geoff saying, ‘It's not up to you whether they accept you. It's out of your hands. If they decide you're too old, that's the way it is.” Of the five schools she applied to, she got into four. She picked Santa Cruz, partly because it was the closest to San Francisco, where her husband was now a cardiologist, and where they now had a child. “Actually,” she said, “two children, by the time I started.”

Debra Fischer
(Tony Rinaldo)

Like Natalie Batalha, Fischer worked on stars, not exoplanets. There simply weren't enough groups working on the topic yet to provide grad students with good research projects, and money hadn't yet poured into the field. Fischer's thesis was on using the element lithium as a marker for stars' ages. But at one point in 1997, she went to an International Astronomical Union symposium in Boston. Geoff Marcy had been there too. “It was a really exciting time,” she said, “because Geoff was talking about the first three exoplanets, which was all they had at the time.” She was sitting in economy, in a middle seat at the very back of the plane, and suddenly Geoff Marcy was standing there. “He'd come back from first class [so clearly
some
money was flowing], and he said, ‘I've been thinking. Paul Butler has this great opportunity to go start an exoplanet project at the Anglo-Australian Telescope, so we'll need another person on my team. What do you think?'” As best as Fischer can recall, her answer was, “Are you kidding? This is so exciting! I will put my whole heart into this project.”

And she did, driving up to Lick late in the afternoon some eighty days a year, taking data all night, then driving back down for her day job, first as a postdoc and then as a research astronomer at Berkeley. “It would be absolutely insane,” she said, “but back then, every planet was a big deal.” It was an even bigger deal when the team found signs of a second planet around the star Upsilon Andromedae, where they had found one already. At this point, no star had yet been shown to have a second planet.

Fischer's job was to take measurements of the star's radial
velocity over many different nights and try to see if they fit a curve. This was how Mayor and Marcy and Latham had been doing it for years. You can't simply aim your telescope on a star and watch it move; you take a reading every so often and plot it on a graph. Today, the star is moving toward you at such and such a speed. Another day it's moving away. Another day it isn't doing much of anything. (This is an oversimplification: Stars are
always
drifting toward or away from Earth as they bobble along in their independent orbits around the core of the Milky Way. The motions Mayor and the others were looking for were on top of that constant, steady drift.)

Over time, those measurements should trace out a curve representing a repeating forward and backward motion—the signature of a planet. If you expect the curve to move leisurely up and down on your graph over years, you wouldn't bother making a measurement every day. That's how Marcy and Butler missed 51 Peg; a planet with a four-day orbit isn't going to show any sort of obvious pattern if you look at it randomly once every few weeks or months.