The 4 Percent Universe

by Richard Panek

  Suntzeff and Schmidt recognized that their team would have to reflect the reality of increasing specialization. As the project evolved from the back of a sheet of computer paper in the spring of 1994 to actual astronomers chewing antacid tablets at observatories, they had to consider not only who would work hard but who possessed what areas of expertise and who had access to the right telescopes. The team's first foray into legitimacy, the September 1994 proposal for observing time at Cerro Tololo the following spring, cited twelve collaborators at five institutions on three continents. After the team confirmed that they'd found their first distant supernova during that run, in early April 1995, Schmidt sent around a reminder of who they were: fourteen astronomers at six institutions. The paper announcing the discovery in the ESO Messenger that fall carried seventeen authors at seven institutions.

  Yet even as the collaboration grew, Schmidt and Suntzeff wanted to preserve the dexterity afforded by old-fashioned astronomy—and to turn their familiarity with that tradition to their advantage. They were, after all, playing catch-up.

  "We can only do it if we're fast," Suntzeff said. "The only way we're going to get this done is if we recruit as many young people as possible." Young astronomers. Postdocs. Graduate students.

  They also wanted the collaboration to be fair. "I'm tired of seeing people get screwed by the system," Suntzeff said—the system where the postdoc did the work and the senior astronomer who had tenure would be first author, getting the credit and going to conferences, while the postdoc wound up without a job.

  By the time Schmidt and Suntzeff gathered their collaborators at Harvard in the late summer of 1995, they had formulated a strategy for delegating responsibilities in a way that would move the project forward quickly and fairly. Each semester, one of the sponsoring institutions—Harvard, or Cerro Tololo, or the European Southern Observatory, or the University of Washington—would be in charge of gathering the data from all the collaborators, reducing it, and preparing a paper for publication. And whoever did the most work on the paper would be the first author.

  Unlike an anarchy, a democracy—even a revolutionary one—needs a leader. In one sense, Kirshner was the obvious choice. But he was also the embodiment of what Schmidt and Suntzeff wanted to avoid; in addition to Go fast and Be fair, they had framed a corollary: No big guns. Back in La Serena in the spring of 1994, when they had made the initial list of potential participants in the distant supernova search, they hadn't even included Kirshner. In his doctoral thesis, Schmidt had used Type II supernovae to derive a Hubble constant of 60, then watched Kirshner crow about it at conferences. Although they'd eventually recognized that sidelining one of the world's most prominent supernova authorities, and a mentor to many in the group, probably wouldn't be wise either scientifically or politically, Schmidt and Suntzeff remained wary of big-gun syndrome.

  And with good reason. At the January 1994 AAS meeting in Washington, Mario Hamuy had given a talk about the Calán/Tololo survey; he was working on an elaboration of Mark Phillips's discovery of the relationship between light curves and absolute luminosity. Afterward, at Kirshner's invitation, Hamuy continued on to Cambridge to give a colloquium on the subject at the Center for Astrophysics. After the talk, a graduate student had invited Hamuy to his office. Adam Riess, not yet twenty-five, radiated the kind of confidence that comes from being the younger brother of two adoring sisters. When he got into the supernova game, he saw no reason why he shouldn't solve the biggest problem out there—how to standardize Type Ia's. Now he wanted to show Hamuy a technique he was developing. Like Phillips's method, Riess's light-curve shape (LCS) allowed you to determine the intrinsic brightness of a supernova; unlike Phillips's method, LCS also provided a statistical measure—a way to refine the margin of error. It quantified the quality of the result.

  Hamuy examined it and told Riess he thought it was, as scientists say by way of praise, "robust."

  Riess, however, said he had a problem. So far he hadn't been able to test the LCS method on real data. Could he see Hamuy's?

  Hamuy hesitated. Your data was your data. Until you published it, it was yours and yours alone. But Riess was persistent, and Hamuy was a guest (at Harvard, of Bob Kirshner), and he relented. Hamuy agreed to show Riess his first thirteen light curves, though not before exacting a promise: Riess could use them only to test his technique, not as part of a paper about the technique.

  A few weeks later, Hamuy got an e-mail from Riess. The technique was working. Riess was excited. Could he publish the results after all?

  That, Hamuy reminded Riess, wasn't part of the deal. But again he relented, though not before exacting another promise: that Riess wouldn't publish his paper using Hamuy's data before Hamuy published his own paper on the thirteen supernovae. Riess would have to wait until Hamuy's paper had cleared the referee stage at the Astronomical Journal. When it did, in early September 1994, Hamuy let Harvard—meaning Riess and Kirshner, as well as William Press, who provided mathematical guidance—know that they were free to submit their own paper.

  They did. But they submitted it to Astrophysical Journal Letters, a publication that, as its name suggests, traffics in shorter papers—and, therefore, briefer lead times.

  Hamuy had to work hard to convince the Astronomical Journal to rush his own paper into print. In the end both papers appeared in January 1995. Both papers used the data to derive a value for the Hubble constant. And both arrived at a Hubble constant in the 60s—Hamuy's "62–67," and Riess's "67 ±7." Forevermore, Hamuy understood, the two papers would be cited side by side, as simultaneous publications.

  "How could I be stupid enough to say okay?" Hamuy moaned to his colleagues in Chile. "'Mario! Mario! Mario!'" he wailed, mocking himself as much as Riess's entreaties.

  Nick Suntzeff could see Kirshner's clumsy thumbprints all over the handling of the timing of the Riess et al. paper. Besides, he was already suffering from his own brush-with-astronomy-greatness fascination. Allan Sandage had encouraged Suntzeff to use CCD technology on Type Ia supernovae to find the Hubble parameter, and Suntzeff had helped his team do so, but the value the Calán/Tololo collaboration derived was on the "wrong" side of 60. Astronomers had estimated that the oldest stars in globular clusters were around sixteen to eighteen billion years old. A Hubble constant of 50 would correspond to a universe that was maybe twenty billion years old; a Hubble constant over 60 corresponded to a universe that was maybe ten billion years old—a universe younger than its oldest stars.

  Suntzeff knew Sandage's reputation even as he was befriending him in the early 1980s. Everyone in astronomy knew Sandage's reputation. Even Sandage knew it. But he couldn't help himself; he took the Hubble parameter personally. He had inherited the program from Hubble himself, he had pursued it for four decades, he had wrestled the value down from the ridiculous mid-three-digits to the realistic mid-two. In the 1970s Gérard de Vaucouleurs had taken it upon himself to challenge Sandage's methodology and assumptions, and he'd arrived at a Hubble constant of 100. Other astronomers had begun finding values that roughly split the difference between 50 and 100. Sandage wouldn't budge. The Hubble constant had to be less than 60, he insisted; the age of the universe demanded it. "The answer will come," Sandage once sneered, "when responsible people go to the telescope."

  And now Suntzeff had joined the ranks of the irresponsible. He had received a note from Sandage, accusing him of having fallen prey to unsavory influences. Suntzeff tried to contact Sandage. Then Phillips tried. But Sandage was done with them.

  Suntzeff, however, wasn't done with Sandage. Having helped derive a value for one of the two numbers in cosmology, he was now mounting an assault on the other. Suntzeff could tell himself that the "competition" with Sandage was in Sandage's head; it was just Uncle Allan being avuncular with a vengeance. He had always known that Sandage might one day turn on him, just as Sandage had turned on other acolytes and colleagues once he thought they'd turned on him. But this business with Hamuy and Kirshner was something else. It wasn't j
ust personally disappointing. It was professionally dangerous.

  Actually, the battle line, as Suntzeff saw it, wasn't Hamuy versus Kirshner. It was Calán/Tololo versus Kirshner. You could hardly blame Riess, an overall affable guy, a graduate student presumably wilting under the will of a powerful mentor. But Kirshner should have known better. Did know better. And didn't care. José Maza, the University of Chile astronomer who had served as Hamuy's mentor, resigned from the collaboration even before the initial observing run in February 1995. Hamuy himself, disgusted and disillusioned, decided that now would be a good time to go back to school for his doctorate; he would be heading for the University of Arizona in the fall of 1995. Suntzeffs colleague at Cerro Tololo, Mark Phillips, adopted a "We have to get past this" attitude; Kirshner had served on the advisory board at Cerro Tololo, and it was Kirshner who told Phillips about 1986g, the supernova that had launched Phillips's and Suntzeffs careers in the supernova game. Yet even Phillips readily acknowledged feeling that what Kirshner had done was "improper."

  And then it got worse, at least from the point of view of the Chilean part of the collaboration. Even before the Hamuy et al. and Riess et al. papers made their simultaneous appearances in January 1995, Riess and Kirshner had submitted another paper using Hamuy's data, this time to study the local motions of galaxies. The Calán/Tololo collaboration felt, as Suntzeff said, "as if blood was shooting out of our eyes." Shouldn't the guys at Harvard have known that it was a subject Hamuy was likely to pursue? Shouldn't they at least have contacted him and offered to collaborate?

  And now, only a month after that paper appeared in the Astrophysics Journal, Suntzeff had to help decide whether Kirshner should lead the team he and Schmidt had created.

  Suntzeff wouldn't be team leader; he had known that from the start. While he wanted to be sure that the Chilean contribution was recognized, he also understood the reality of his situation.

  "I'm a staff astronomer in Chile," he told Schmidt. This kind of project would take a 100 percent commitment, and he already had a full-time job—and that job was in a place that left him "really isolated." But there was an even more important consideration, he argued: The post would need someone who could bridge both worlds—or both hemispheres, anyway. It needed Schmidt.

  In terms of leading the team, Schmidt was equal to Kirshner in all ways except seniority. He'd helped found the group. He'd led the charge in Chile. Perhaps most important, he was no longer at Harvard; he'd moved to Australia earlier in 1995 (a fourth continent!). And over the past several years, both as a postdoc and now on his own as an astronomer, he'd been in Chile often enough to know everyone there well and for everyone there to trust him.

  Schmidt was reluctant. But he was also the guy who thought he could write code in two months.

  "Yeah," he finally told Suntzeff, "I can do it."

  Suntzeff campaigned quietly on Schmidt's behalf. Brian, he argued, had the personality to hold the group together, and he had the drive to get the job done. Eventually Suntzeff talked to just about everyone in the collaboration. Everyone except Kirshner.

  Kirshner campaigned on his own behalf. His argument was that he knew the supernova game better than anyone. To a large extent, over the past quarter of a century he had made the supernova game what it was. He had a long history of writing proposals, securing support, keeping collaborators together. He reminded the team members that having all this young talent together in one place—the Harvard Center for Astrophysics—was "not an accident." He was the one who identified the promising graduate students; he was the one who hired the postdocs. "That's something," he told them, "that has to do with making a place where this subject is being done at the highest level."

  The more he talked, the more he sounded like a big gun.

  The team met in a seminar room in the basement of the Center for Astrophysics. Kirshner and Schmidt waited outside. After a short while, the door opened.

  The Big Gun was out. The Young Turk was in.

  Schmidt had learned his lesson: This time he went to Chile.

  And not only did he go to Chile for the fall 1995 observing season, he got there nearly a week early to test the new code he'd written. He immediately discovered that it didn't work. He was still at the mercy of the observatory's computers; if aspects of the computers had changed since he wrote his code back home in Australia, then he'd have to rewrite his code. The first day in Chile he worked ten hours trying to fix it. The second day he worked twelve or fourteen hours. Third day, sixteen or eighteen. Fourth day, twenty, and then twenty hours the next day, and twenty the day after that. When he started running a fever and having heart palpitations, Schmidt figured it was time to sleep.

  Given the standard scheduling logistics at telescopes, his team had had to apply for time at Cerro Tololo the previous spring, even before they'd found their first distant supernova. If they hadn't discovered 1995K, who knows if they would have received the time? If they hadn't satisfied themselves that it was a Type Ia, who knows if they would be using the time, or at least using it to search for distant supernovae? But they were a true team now; they'd even put the idea of distant supernovae in their name: the High-z team (z being the symbol for redshift). It had all worked out, though when Schmidt had told the team via e-mail that they'd gotten time on the telescope, he'd added, "The bad news is that Perlmutter has more nights."

  The two teams had applied for time during the same observing season, and the Time Allocation Committee at Cerro Tololo had taken the Solomonic approach of assigning the teams alternating nights. To make the situation even more awkward, one of Nick Suntzeffs duties at the observatory was to provide technical assistance to visiting observers. On nights that he wasn't participating in his own team's search for supernovae, he was, grimly, watching over Saul's. The objective astronomer in him found the Berkeley team's work "quite impressive." Personally, though, he could only shake his head and deliver his verdict to his collaborators: "They're well ahead of us."

  The corks were still popping, one for each supernova, but now most of the champagne was going down the drain.

  During that observing run at Cerro Tololo in the fall of 1995, the SCP team discovered eleven more supernovae, in one run doubling the number they had gathered over the preceding three years. They had mastered the technique. Astronomers gathered data in Chile, forwarded it to their colleagues in Berkeley, who passed along the information to colleagues at the new 10-meter telescope at the W. M. Keck Observatory in Hawaii, where the team had already secured time because they knew, months in advance, that they would have supernovae to observe on that date. For the astronomers at the telescopes, the observations still contained drama: corrections to code, struggles with weather, decisions on what to target, bouts of diarrhea, and, in Chile, the occasional earthquake. But back in Berkeley, the overnight delivery of data was becoming routine. After all, in a universe full of billions of galaxies, stars were exploding all the time. Supernovae were out there by the thousands, by the millions, every night, waiting to be harvested. The Berkeley team had refined their collaboration, turning it into the kind of assembly-line operation that Alvarez and Muller had foreseen nearly two decades earlier. They were producing the intuitively paradoxical and once unthinkable: "supernovae on demand."

  Somewhere in the universe, a civilization died. In Berkeley, they yawned.

  In January 1996, at the AAS meeting in San Antonio, Saul Perlmutter sought out Robert Williams, the director of the Space Telescope Science Institute—the scheduling headquarters for the Hubble Space Telescope. Perlmutter wanted to talk about the "batch" method.

  "I think with this technique," he said, "we now have the possibility, for the first time ever, of applying for HST time to follow up these very high-redshift supernovae." He explained that by now the SCP team had discovered twenty-two distant supernovae—mostly Type Ia—through the batch method. They had proven that they could predict the date they would find supernovae: whenever they got telescope time. And they could predict where:
among whichever thousands of galaxies they chose to scour. They could guarantee the discovery of supernovae. The choice of when and where was now theirs, not the night sky's.

  HST required just that level of certainty. It wasn't like earthbound telescopes. You couldn't just submit a proposal and six months later show up with a finding chart. The instrument required extremely complicated programming; you had to have your metaphorical finding chart in hand months in advance, with very little leeway for last-minute (actually, last-week) adjustments. Perlmutter's argument was that this kind of preparation was what the batch method allowed. The combination of confidence and specificity could meet the intricate dance of demands that came with booking time on the Space Telescope.

  The logistical details would still be daunting, but they'd be worth it. The Hubble Space Telescope didn't see a lot; its field of view was minuscule compared with the old 200-inch or new 10-meter behemoths on terra firma. But what it saw, it saw with a clarity that no other telescope could approach. Through a CCD camera on an earthbound telescope, a very distant galaxy appeared as a smudge of pixels. Subtracting the light of the galaxy to isolate the light of the supernova was difficult work; witness the four months Leibundgut needed to figure out that the "very faint" 1995K was a Type Ia. The high resolution of HST, however, would make a supernova pop out of its host galaxy. Subtracting the light of the galaxy would be not only easier but far more precise.