The reason Borucki hadn’t announced any new results at the Washington press conference was that he’d already presented everything he had just two weeks earlier, at a press conference at NASA headquarters, in Washington. There was plenty to say: In just the first six months’ worth of observations, Kepler had come up with no fewer than 1,235 possible planets, about 90 percent of which were almost certainly real. Kepler had barely warmed up, and it had identified at least twice as many planets as all the astronomers in the world had found in the previous sixteen years. “Astronomers have cracked the Milky Way like a piñata,” Dennis Overbye wrote in the New York Times, “and planets are now pouring out so fast that they do not know what to do with them all.”
After he gave reporters the number of new planets—or, rather, “planet candidates,” in the very careful language Kepler scientists prefer to use—Borucki explained, like a pollster projecting the outcome of an election based on just a small sample of voters, that Kepler is looking at only about 1/400th of the sky. If the spacecraft had been able to monitor the whole, he said (or if NASA had sent up four hundred identical Keplers, pointing in all different directions), they’d be talking not about twelve hundred planets, but about the more than four hundred thousand the probe would undoubtedly have seen.
It was a terrific story—two weeks earlier. The talk at the American Association for the Advancement of Science meeting was pretty much just a replay. For a science reporter—especially a reporter for the Associated Press, where late-breaking news is a specialty—that just wasn’t good enough. Borenstein couldn’t write a story that said, in essence, “The Kepler results announced two weeks ago are still true.” So, while the editor of Discover magazine and I stood by, looking on in comradely amusement, Borenstein kept pushing the Kepler team leader to say something new. Borucki was clearly reluctant to be pushed.
“Okay, so if I understand you correctly,” the reporter asked, “you said you’ve found 1,235 planet candidates, right?”
“That’s right,” said Borucki. He’d said this two weeks earlier. Borenstein knew it. But like a prosecutor in a courtroom, Borenstein was building his case.
“And of those, fifty-four are in the habitable zone of their stars?”
“Yes, that’s correct.”
Again, this news was two weeks old, but it was really important. The habitable zone is the orbital band surrounding a star where the temperature allows water to exist as a liquid rather than as ice or vapor. It’s sometimes called the Goldilocks Zone, even by astronomers—even on NASA’s website—since like the porridge in the fairy tale, it’s not too hot and not too cold, but just right. Biologists have long insisted that water is essential for life, because nutrients can dissolve in it easily, to be distributed to every part of an organism. That’s what blood does for most animals, and blood is mostly water. Life on Earth wouldn’t be possible, says the conventional wisdom, if most of our water boiled off into the atmosphere or froze solid. Earth is inhabited because we live within the Sun’s habitable zone.
If you’re interested in finding life on other worlds—and that’s what just about every scientist who hunts for planets is ultimately looking for—planets in the habitable zone are what you want. Planets about the size of Earth in the habitable zone are even better. The question of whether life exists beyond Earth is one of the oldest mysteries of nature, dating back at least to the ancient Greeks, and probably even further. At some times in history, the notion of alien life has been considered heretical; at others, learned men took it as a given that planets, both within and outside the solar system, were home to intelligent beings. The eighteenth-century astronomer William Herschel, who discovered the planet Uranus, was convinced that even the Sun was inhabited (he had a handy explanation for why the Sun creatures weren’t incinerated).
Kepler isn’t capable of answering the question of whether life exists on other worlds, but it can take the first step by finding an Earth-like planet, a Mirror Earth, where life could be thriving, at least in principle. Kepler was designed with several scientific objectives in mind, but number one on the list that appears on the mission website is this: “Determine the abundance of terrestrial [that is, Earth-size] and larger planets in or near the habitable zone of a wide variety of stars.”
“So, as I understand it,” continued Borenstein, pressing his interrogation, “there are about 300 billion stars in the Milky Way. If you’re looking at 150,000 stars, and found 1,200 with planets, and 54 of those in the habitable zone … that means …” The reporter stared at the ceiling, wheels turning in his mind. Borucki looked on, politely. “… there should be something like 50 billion planets in our galaxy, right? And 500 million should be in the habitable zone.”
Borucki thought about that for a moment. “Yes, that sounds right,” he answered.
Two weeks earlier, Borucki had talked about a hypothetical four hundred thousand planets that could be detectable from Earth. Now, under intense, though friendly, questioning, he was admitting to five hundred million overall. Borenstein had his story. Later that day, the Knight Science Journalism Tracker, a blog that aggregates and reviews science stories, described it this way:
Seth says 50 billion planets, minimum, in Milky Way. Nobody said that at the press conference. Minor consternation ensued among other reporters after he filed. How’d he get that angle? Explanation: Seth missed the press conference. Saw Borucki afterward talking with a few reporters including Michael Lemonick of Time. “Just a nice chat where you riff together,” Borenstein says. Borucki says one in two stars has planets, Seth says let’s do the math, Borucki complies and double checks, and that’s why it can pay to be there in the flesh.
This remark about the flesh may well have been a dig at media outlets that are no longer willing to pay for reporters to go to conferences. The author of the blog post, Charles Petit, covered science for the San Francisco Chronicle for years, and takes a dim view of how his profession has been downsized. Still, the calculation done by the AP reporter was so simple and obvious that Borucki could easily have done it for the other reporters who were present, and for the hundreds more who get NASA press releases by e-mail. He could have done it for the press conference two weeks earlier.
The fact that he hadn’t says a lot about Bill Borucki. Some astronomers are showmen—Neil deGrasse Tyson is a good example. Tyson, the director of the Hayden Planetarium in New York, is a serious and highly respected scientist, but he’s also a frequent guest of both Jon Stewart and Stephen Colbert on Comedy Central. When he taught at Princeton (he had a part-time appointment to the faculty there for many years), his dynamic lectures drew students by the hundreds. Tyson is a tall, powerfully built man in his forties, a former athlete and dancer who once told me that “in high school, I was a nerd, but a nerd who could kick your butt.” I once saw him at an astronomy conference striding across the hotel lobby in a form-fitting black workout outfit, complete with weightlifting gloves—a ninja astronomer heading for the gym. Every eye in the place followed him.
That makes Bill Borucki the anti-Tyson. He’s in his early seventies, below average in height, with thinning hair and wire-rimmed glasses. He speaks softly where Tyson booms, and he pauses before he answers a question, where Tyson fires rapidly. Borucki wouldn’t do well on The Colbert Report. His talks are generally delivered in a thoughtful, measured tone, without laugh lines or oratorical fireworks. Bill Borucki would look ridiculous in a black workout suit. Wearing a coat and tie, as he was when Borenstein cornered him after the Washington press conference, he could be mistaken for an accountant. In the more relaxed atmosphere of a recent astronomy conference, he ambled through the Washington State Convention Center in Seattle in a green windbreaker, looking like someone Hollywood might have cast as the clerk at an old-fashioned hardware store. Tyson grew up on New York’s Upper West Side; he has an undergraduate degree in physics from Harvard and a Ph.D. from Columbia. Borucki grew up in Delavan, Wisconsin, in the space-happy 1950s. He built model rockets and, as head of
the high school science club, organized the construction of a transmitter to contact UFOs. His undergraduate degree in physics comes from the University of Wisconsin, in Madison, and he has no Ph.D. at all—just a master’s in physics, which he also got at Madison, in 1962.
Bill Borucki (Courtesy of NASA)
Borucki’s temperament is cautious enough that any calculation he might do for a press conference would tend to involve as little speculation as possible. When he came up with the figure of four hundred thousand planets across the entire sky, he was talking about planets that Kepler could in principle have detected if it was pointed in their direction. When Borenstein came up with five hundred million, he was talking about planets anywhere in the Milky Way, most of which couldn’t be found by Kepler, or, for that matter, by any other telescope that could conceivably be built.
Beyond that, it would be easy for the general public to leap to premature conclusions about what Kepler had actually found. The fifty-four planets Borucki had announced in the habitable zones of their stars weren’t necessarily anything like Earth. Many of them were much bigger—as big as Neptune or even Jupiter—and therefore not a place you could easily imagine finding life. Also, they didn’t orbit stars like the Sun. They orbited red dwarf stars, which are significantly smaller and dimmer, and whose planets might not be good places for life to take hold. Sixty-eight Earth-size planets he’d also talked about, conversely, weren’t in their stars’ habitable zones, so there wasn’t much chance of life there either.
In other words, the true story was a little complicated and a little subtle. There’s often a tension between the reporter’s need to have the most exciting story possible and the scientist’s need to avoid too much hype. Borenstein walked that line like a tightrope. The story that came out of the Borucki-Borenstein encounter was absolutely accurate, but while it might have seemed otherwise to a lay reader, there was no new science in it—just a small victory for a reporter in his respectful but relentless tug-of-war with a scientist.
Talking to the press wasn’t a problem Bill Borucki had to deal with much in the early part of his career. His master’s degree was enough to get him a job in the early sixties at the Ames Research Center, at Moffett Field, near Mountain View, California. His first assignment there: to help design heat shields to protect space capsules from burning up as they reentered Earth’s atmosphere. The only breaking news on heat shields happened when Mission Control feared that the shield protecting John Glenn’s Friendship 7 capsule had worked its way loose during his first orbital flight, in 1962. If it had fallen off he would have been incinerated—but it wasn’t loose after all. Even if it had fallen off, the heat shield itself wouldn’t have been to blame.
During a visit to Ames in October 2010, I suggested to Borucki that the Kepler project was probably a lot more exciting than this first project must have been.
“Oh, my God,” he said, his eyebrows rising with either dismay or pity, or maybe a little of both. “You don’t know anything about heat shields, do you?”
“But … planets orbiting other stars,” I protested feebly. “It’s something the human race has dreamed of for thousands of years …”
“But imagine this reentry vehicle coming in,” he protested back, “heating the shock wave in front of it to many thousands of degrees hotter than the surface of the Sun. That is interesting! Hotter than the surface of the Sun, and we’ve got to calculate the heat radiation on this shield—otherwise the astronauts die on their way back. That’s a pretty impressive thing to work on.” It was also a challenge: At the time, nobody had a very good idea about how to calculate what happens to air when you heat it up to tens of thousands of degrees. So Borucki and his colleagues began studying lightning, which does exactly that—taking images of the flashes and analyzing the light for evidence of what was happening to air molecules at these temperatures.
At the end of the 1960s, Borucki left the exciting world of heat shields. “After the day we were successful getting to the Moon,” he said, “I moved over to the theoretical studies group at Ames.” It wasn’t as drastic a move as you might imagine, however, because he was still studying lightning. Except this time, the lightning was on Jupiter. Scientists using radio telescopes had detected bursts of static coming from the giant planet and suspected that lightning was the cause. Borucki and his colleagues wanted to understand how lightning on Jupiter might differ from lightning on Earth.
At first they were stuck with building laboratory experiments to simulate Jovian lightning, since at that point nobody had gotten a close look at the planet itself. They created miniature Jupiter atmospheres inside what amounted to huge test tubes. Then they fired lasers into them, which triggered electric sparks. And then they studied the flashes, just as they’d done with real lightning a few years earlier. In both cases, they had to build detectors that could measure changes in light with extraordinary precision. “You’re trying to understand the fundamental measurements, you’re trying to understand their time dependence, you’re building photometers that people generally don’t build that are running on the nanosecond level,” said Borucki. When space probes finally detected the real thing during flybys of Jupiter in the late 1970s, the work Borucki had done helped planetary scientists understand what was happening on the giant planet itself.
At about the same time Borucki was trying to understand lightning on Jupiter and the nature of the atmosphere that gave rise to it, he said, “there were seminars here at Ames. People would come and talk about future projects, going to Mars and finding life and things like that. Those were very inspirational, and I began to think about whether what I knew could help solve the problem of whether there’s life in the galaxy.”
His experience with model rocketry notwithstanding, Borucki didn’t know much about going to Mars or designing experiments to look for life. He didn’t know much about SETI, the Search for Extraterrestrial Intelligence, which his colleague Frank Drake had been working on since the early 1960s. Drake’s idea was to listen with radio telescopes for the broadcasts, deliberate or inadvertent, that might be coming from alien civilizations. SETI is what Jodie Foster was doing in the movie Contact, although, naturally, with a little more drama and romance than the real thing.
In thinking about the search for life on other worlds, Drake had quickly realized that if alien civilizations really existed, they probably needed planets to live on. Not just any planets: They needed, as far as anyone knew, planets that were at least vaguely Earth-like, orbiting in their stars’ habitable zones. In the 1960s nobody knew how many of these there might be in the Milky Way, if any at all. But Drake went ahead on the assumption that they must exist, given the vastness of the Milky Way. By the 1980s, astronomers still didn’t know. They didn’t even know if planets of any sort existed, Earth-like or not. A tiny handful of planets had been “discovered,” starting in the 1960s, but every one of them had been undiscovered later on. The original detections had simply been mistakes.
Borucki thought maybe he could do better. He knew there was no way to see planets around other stars directly. Everyone knew they would be too faint, hidden in their star’s much brighter glare. The astronomers who had made those earlier, false detections had used another method entirely. They’d looked at the stars themselves, hoping to see them wobble in place as the gravity of an orbiting planet tugged them just a tiny bit—first one way, then the other, as the planet circled from one side of the star to the other. This technique is known as astrometry, meaning “star measurement.” The motion would be tiny, thus very difficult to see, because a planet is tiny compared with a star. It’s not a huge surprise that those early discoveries were mistakes.
Partly as a result of these false detections, and partly because any sort of detection was impossible with any existing telescope, the search for planets around other stars had become a scientific backwater. There wasn’t much point in looking until someone—NASA was the obvious choice—provided astronomers with powerful new instruments. If you can’t
see a tiny motion with an ordinary telescope, went the reasoning, build a gigantic telescope—or, since that’s really expensive and impractical, use a group of smaller telescopes at one time to simulate a single, huge one. “People had sketched out systems that might do this,” said Borucki, but it turned out to be a lot more difficult and expensive than anyone thought. (It wasn’t until 2009 that two astronomers, using technology far more sophisticated than anything available in the 1980s, finally announced they’d found the first planet ever discovered with astrometry. NASA put out a press release with the headline PLANET-HUNTING METHOD SUCCEEDS AT LAST. But it hadn’t. That discovery, like the earlier ones, is now widely considered to have been a mistake.)
Borucki had no expertise in measuring the positions of stars in the sky, but he did know how to measure light. “I said to myself, ‘Here’s another way to do it. It’s a rather simple way. It doesn’t require the kind of extreme equipment you need for astrometry.’” So in the summer of 1983, he sat down with a colleague named Audrey Summers and wrote a paper titled “The Photometric Method of Detecting Other Planetary Systems.”
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