A Lonely Stargazer, With A Lot Of Help From His Friends

Although a five-member international team of astronomers recently took credit for identifying what appears to be a previously unknown planet, the thrill of first noticing the heavenly body belonged to a single individual, Robert Stefanik. Working in solitude late one night at the Oak Ridge Observatory 30 miles outside of Cambridge, Mass., Stefanik, using a 55-year-old telescope, detected an almost imperceptible wobble in the motion of a star some 90 light-years from Earth. It was this lone scientist’s vigilance in staring at a star 522 trillion miles out in space that set the Smithsonian Astrophysical Observatory’s team onto its path toward achievement. The loneliness of the long-distance stargazer has always been a part of the astronomer’s discipline, observes one of Stefanik’s teammates, Tsevi Mazeh. “In the end,” Mazeh says, “there is only one person or a couple of persons sitting through the whole lonely night behind the telescope. In a sense, astronomy is still a life for people who like to be alone.” As it turned out in Stefanik’s case, the minute periodic variation that he noticed in the radial velocity of the star—listed as HD 114762 in the Henry Draper catalog of stellar spectral types—was subsequently determined to be caused by the gravitational pull of a low-mass companion, probably a massive planet, with an orbital period of 84 days. At the time he noticed the wobble in the star’s rotation, however, Stefanik didn’t realize he might be seeing the effect of a “new” planet until someone on the Smithsonian team performed a statistical analysis of his observation. This fact, according to David Latham, the astronomer who heads the Cambridge-based team, reports the idea that, in modern astronomy, team efforts away from the telescope are increasingly necessary. “You’ll still find some astronomers that are quite traditional, working almost by themselves,” says Latham. “But there’s a trend, especially with observational astronomy, to have more people on the team because so many skills are required. You need the instrument makers and the people who know how to do the statistical interpretation of the ob- servation, and the people who work on the theoretical interpretation.” The team’s recent discovery, he notes, required international cooperation, diligent observation by a staff with a dedicated telescope, and a little luck. “It isn’t like we just went out one afternoon and said, ‘Well, let’s discover a planet,’” says Latham. “We’ve put together people with different experi- ences and talents, and the combination is more powerful than the individual components.” The Smithsonian team began taking on its current shape and focus four years ago, when Mazeh, professor of physics and astronomy at Tel Aviv University, approached Latham to find out if he could spend his sabbatical year working at the Cambridge facilities. He suggested using the velocity measurement instruments already in place at SAO to look carefully at selected stars for evidence of low-mass companions. Latham agreed to the planet search project, and was pleasantly surprised by how well the data accumulation and analysis projects progressed. As the low-mass companion work advanced, team members began developing a new instrument with improved precision in the measurement of very small variations in stars. Stefanik, director of the Oak Ridge Observatory, worked on the instrumentation with Latham and with SAO physicist John Geary. To test the new instrument for the first time, the astronomers wanted to observe something very bright and something that did not vary. Coincidentally, for seven years the team had been observing a set of standard stars as a service to the astronomical community. The standard stars are intended to provide a yardstick by which astronomers worldwide can compare data and test new instrumentation. As director of Smithsonian’s Oak Ridge facility, Stefanik had accepted primary responsibility for the project and performed or supervised almost all observations of standard stars. “Not many places go to the trouble of making these boring and rather unrewarding observations,” says Latham “And Robert [Stefanik] took charge of the service operations without anticipating the kind of payoff that eventu- ally came out of it.” Stefanik’s unexciting but altruistic efforts did not go unrewarded, however. The standard stars were just what the team needed to test the instrumentation, and the data he had accumulated proved crucial to verifying its planetary identification. On an evening late last March, he made his first observations using the new piece of equipment, and while he was pleased, he was also a bit puzzled: The data from six of the seven stars he looked at on that first night fit in with previous findings—but he wasn’t quite sure what was going on with the seventh. Then, in the early hours of April 1, Latham—using a software program developed by Mazeh—was reducing the data from Stefanik’s first observations with the new instrument. When he saw that one of the stars had a big deviation, he was concerned. “I wanted to believe the new instrument that we spent a whole year developing, was working right,” Latham says. “I wanted to blame the star.” The only way for Latham to implicate the star and vindicate the instrument was to go back through the seven years of data the SOA had accumulated on the standard stars to see if the same wobble in HD 114762 had been present, although undetected, in the past. It had been, he determined. “It was probably one or two in the morning, and I immediately called to Stefanik, who was working at the telescope that night,” says Latham. The two have been friends and colleagues since 1961, so Latham decided to play a little trick. “I said something like, ‘Robert, you screwed up! What the hell’s wrong with HD 114762?’” But when they discussed Latham’s finding, the two were excited and agreed that they might finally have found a low-mass companion—exactly what they’d been searching for. Even so, they had learned to be cautious and decided to double the number of observations they already had with independent data. “That was the beauty of this thing,” says Latham. “It has an 84-day period, so we could do it in just three months. A lot of these things take thousands of days, so you have trouble living long enough to check them out.” In the meantime, in search of additional confirmation, Latham contacted Michel Mayor at Switzerland’s Geneva Observatory, which has been collecting data on the standard stars for 10 years. “I sent my results to Michel Mayor on April 1 without a moment’s hesitation, saying ‘Here’s the period, here’s the object, what have you got?”’ says Latham. When Latham’s sister, a molecular biologist, found out how freely he shared his data she was appalled. But that’s the way Latham operates. “The chemistry has to be right, though,” says Latham of his unusually trusting attitude. “You can’t just put any people together—there has to be a kind of unspoken, unwritten matching of the personalities with sharing and trusting of each other.” Based on Mayor’s data taken with colleague Gilbert Burki both in France and Chile, the Swiss astronomers were able to confirm the variation. “I looked in my files,” he recalls, “and I discovered 64 observations with exactly the same period of the star as Dave [Latham] had looked at. I arrived at the same amplitude with the same phase for variation. This was a very good thing—that we discovered exactly the same phenomenon with two independent observer instruments.” The most exciting extension of their work, Latham says, would be to discover planetary systems—to find a system analogous to our own solar system where a star has a whole family of low-mass companions. “That’s really important, because if you have a whole flotilla of these things, spaced out at different distances from the star, then it’s very likely that you’re going to have one at just the right distance for the temperature to have liquid water—and we have a prejudice that you need liquid water for life.” In search of evidence for more low-mass companions, and perhaps even life, Latham’s team plans to continue collaborating with Mayor and will carefully review some of the other standard stars that both groups have been studying. And what about Mazeh? After completing his sabbatical, he has remained a member of the Smithsonian team and a major contributor to the theoretical understand- ing and numerical processing on the project. Mazeh has returned to Cambridge at least once a year since his year-long stay, most recently for the International Astronomical Union meeting in Bal- timore where the team announced its findings. For Stefanik it’s back to the telescope. “We’re just plugging along. It [the recent discovery] makes us feel some of this routine stuff is worth doing,” he says of his standard star observations.

A Lonely Stargazer, With A Lot Of Help From His Friends

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