The Long Shot

Feature / by Lee Billings /

Two rival scientific teams are locked in a high-stakes race to discover other Earth-like worlds—and forever change our own.

Debra Fischer. Courtesy of Debra Fischer.

“One night we were talking and I told her I wanted to do more science stuff,” Walp recalled. “I’ll go to my grave remembering her response: ‘Oh, well, let’s fix your job! Pack a bag, tomorrow night we’re going to Lick Observatory!’ I fell in love with the mountain, the telescopes, and the people—ended up applying for a job and working there…. Debra had not only fixed my job, she’d fixed my life.”

For Walp, astrophysics is a communal embrace, not like the solitary work of mathematics or the faceless, overlarge collaborations of particle physics. “In astrophysics, even if you’re just a student, you’re encouraged to find new ways of doing things,” he said. “Build a piece of equipment, drive it to the observatory, bolt it on the telescope, get some data, write it up. I find that very attractive. In politics it was all turf, a zero-sum game. You just don’t have that in this environment. Everyone helps each other.”

He paused, eyes sparkling and fixed on something distant. When he spoke again his voice was soft, quiet. “My wife died kind of tragically last year…. I decided it was time for a change, and left Lick to go to Mount Wilson to be closer to my family. Debra needed help setting this up and invited me. I graciously accepted.”

Walp is just one of a small army of friends and colleagues Fischer relied on to get the venture off the ground. It needed dedicated equipment—a telescope, a spectrometer, and a photon detector—all either custom-built or leased from existing facilities. It needed improvements to Fischer’s planet-hunting software, the computer code that extracts RV signals from massive influxes of data. Most of all, it needed funding. Fischer began methodically obtaining each piece of the puzzle, sometimes calling in old favors. In late 2007, along with Laughlin and another astronomer, Paul Butler, she applied for an NSF grant and received nearly $100,000 for a one-year “design study.” This was enough to pay for telescope time on a 1.5-meter telescope at CTIO that was on the verge of being mothballed. Andrei Tokovinin, an astronomer at the observatory, offered to refurbish a decommissioned spectrometer for Fischer and provided an old, outdated detector. The cutting-edge observations would take place on vintage equipment from the 1960s and ’70s.

“Andrei’s been a lifesaver,” Fischer said as we approached the 1.5-meter telescope’s white dome housing. “We don’t really have money for anything other than telescope time. We can’t afford a salary for me or stipends for my students. It’s like being in a sinking ship, throwing everything else overboard just to keep moving forward.” When the NSF funds run out in November, Fischer plans to ask for only one more year’s worth of money for what may be a project spanning several years; such a modest request may be more difficult to turn down. She’ll be relying on any promising, early signals in her data, hoping they strengthen from one year to the next to provide further incentive for financial support.

The dome’s interior was cavernous, cool, and dark, reverberant with hushed echoes. Walp turned on the lights in the control room, revealing the 1.5-meter as a hulking cylinder in an equatorial mount with a multi-ton, cast-iron counterweight, hovering in the center of the room above the corrugated metal floor. Fischer, laughing, said it’s the smallest telescope she’s worked with, and walked me through the tortuous path photons follow through the experiment.

Imagine a hundred photons leaving Alpha Centauri almost four and a half years before my January visit to CTIO. Back then, George W. Bush was winding down his first presidential term, the Summer Olympics were underway in Athens, the stock market was soaring, and the Cassini-Huygens mission had just arrived at Saturn. After years of continuous interstellar travel, that light entered the dome at CTIO. It bounced off the large primary mirror, back toward the sky, only to be reflected by a secondary mirror into a Cassegrain focus, a small hole in the primary mirror’s center. For every 100 photons from Alpha Centauri that hit the primary mirror, 20 were lost en route to the focus. From the focus, the light entered a long, winding fiber-optic cable, stabilized by duct-tape, running into the spectrometer in the basement below. Another 20 out of 100 photons dropped out in the fiber. The light passed from the fiber through an iodine cell used for calibration, into the cryogenically cooled spectrometer, where a labyrinth of prisms, mirrors, and gratings scattered, split, and chopped the light into its constituent wavelengths. Of the 100 photons we’ve followed from Alpha Centauri, only one managed to navigate the obstacle course of the telescope, the fiber, and the spectrometer to strike the detector, where it was logged into Fischer’s data.

From there, the rest of the work takes place on computers. For each one of the hundreds of thousands of observations, Fischer’s custom-coded software must model and counteract the various transient distortions caused by the instruments, fluctuating weather and temperature, cosmic rays striking the detector, even the Earth’s motion through space. The software compares the observed spectra of Alpha Centauri A and B to a spectrum from the calibrating iodine cell, then to a high-resolution spectrum of both stars taken through a larger telescope with a newer spectrometer. This comparison provides the wavelength shift, which is calculated and plotted for each observation. With enough time and sufficient numbers of observations, any planets around either star should manifest as tiny periodic shifts in the light’s wavelength.

Fischer wrote the code that makes the data analysis possible, but she still expressed amazement that the technique actually works. “Take our Sun. It’s a quiet star, but look at it in ultraviolet, and you’ll see all these flares boiling, wild coronal loops that break and spray out particles, plasma flowing across its surface at kilometers per second,” she said. “We can measure the Sun’s dynamical motion to a thousandth of that because, by some miracle, these surface motions average out over the disk. But at what point this stops, we don’t know. The sensitivity floor for this technique is unknown.”

The afternoon was gone, eaten by the hike and discussing the experiment. Fischer decided to take a break. We emerged from the dome into a still evening awash in molten, honeyed light. Long purple shadows twisted like veins through the craggy valley below, and the russet pinpricks of sodium lamps from a small mining town sparkled in the distance. Beside a few battered pickup trucks in the asphalt parking lot, Christian Nitschelm, a jovial, frizzy-haired Franco-Chilean astronomer, was watching the Sun. He was waiting for the “green flash,” the brief instant immediately before the Sun wholly disappears beneath the horizon, when its rays pass through so much atmosphere that they refract to a vivid emerald hue.

Nitschelm held an index card several centimeters in front of the eyepiece of a small hobby telescope, catching the Sun as a featureless, diminishing disk, judging when it would be safe to view directly. He chatted idly as he waited. “The Sun is quiet now. No one knows why. It should’ve already started its next cycle; sunspots should have appeared months ago. But I see none.” After a moment he motioned me to the eyepiece—it was time. A green tint appeared around the upper edge of the Sun’s wavering face, traveling inward until the entire final glimpse was the color of chlorophyll. Then we were in twilight.

Like people, stars are statistically predictable, but as individuals they often flout forecasts. The Sun’s 11-year cycle of activity is inexplicably late this time around—we still have much to learn about our very own host star. Similar cycles with periods of months or years on Alpha Centauri A or B could scuttle Fischer’s hopes for finding planets around either star. This possibility is what most worries Geoff Marcy, Fischer’s mentor and a professor at the University of California, Berkeley. As one of the founders of RV planet discovery, Marcy is a de facto leader of the American planet-hunting effort.

“We have global circulation patterns on Earth,” Marcy told me via telephone. “Trade winds, tropical winds, and so on. Similarly, our Sun and other stars have their own circulation patterns. These cyclic motions of a star’s surface could easily masquerade as the motions caused by an Earth-like planet. Debra is one of the very rare astronomers capable of marshalling all the necessary resources for this project—telescope time, funding, and collaborators. But she can still be fooled. We could all be fooled!”

Or, Marcy fretted, a competing team of researchers could find Alpha Centauri’s planets first.

Tags data research space theory

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