There's No Place Like Home? 

Not so fast, Dorothy! It looks as if Earth may not be so special after all. Second in a two-part series.

Page 2 of 6

Twenty years ago, Geoff Marcy bet his career on more or less the same thing. He was a postdoctoral fellow with the Carnegie Institute, stationed at the Mount Wilson hundred-inch telescope near Pasadena. And according to him, he stank. "I could tell I didn't have the right stuff," he says. "I was done, I was over, I was cooked. I couldn't do astronomy."

Convinced that he could do no more than kill time until his fellowship ended and he began his inevitable career change and slide into obscurity, Marcy decided that he might as well kill time while doing something really wild, like trying to find planets.

People thought this was nuts. Unlike stars, planets don't emit light. They reflect a little light from their host stars, but they are a billion times fainter. Nobody knew how to find them with an optical telescope. As Marcy puts it, "There is no way to find a firefly next to a nuclear explosion."

Then one day while standing in the shower and despairing, which Marcy says is the only way he did anything during those years, he came up with a way to find planets without seeing them. He would use the Doppler effect, the same technique a cop's radar gun uses to pinpoint your car's speed. "In my case," he says, "I was going to use the starlight to measure the speed of a star."

Here's how: Even though planets are much smaller than stars, they still exert a tiny gravitational tug on them. That tug makes the star wobble ever so slightly. If you watch a star night after night, measuring the wavelengths of light it emits, you can see a distinct pattern to the wobble that corresponds with how long it takes for the planet to orbit the star.

It was a nice idea, but science is built on evidence, of which he had none. Worse, the concept of looking for planets sounded pretty flaky. Marcy recalls, "When I would tell people, 'Gee, I'm thinking of hunting for planets,' eminent astronomers would look at me for a moment to see if I was serious and then they would look down at their shoes, their feet would kind of shuffle a little bit while they were uncomfortable, wondering if I was serious and whether they should believe me that I'm really going to look for little green men."

Nevertheless, when his fellowship was over, Marcy was offered a professorship in the Bay Area. "San Francisco State had no telescope, no computers, and no money," he says drily, "so we were in pretty good shape for planet hunting." He recalls that his budget for his first year was $900. "I didn't want to embarrass myself by asking for regular funding to search for planets, because you might as well ask the National Science Foundation to investigate pyramid power."

What SF State did have was an eager grad student named Paul Butler, who made a major contribution to Marcy's idea. In addition to measuring changes in the wavelengths of light emitted by a star as it wobbled toward and away from the Earth, they would create a baseline against which to track the changes. Butler's idea was to attach a cell of warm iodine gas to the telescope's optical system. The immobile cell has an unchanging chemical spectrum, and by superimposing its stable spectral image onto the star's changing one, you can measure stellar movements in fine detail.

It wasn't quite as easy as it sounded. "For eight years, from 1987 to 1995, Paul and I worked every day of the week," Marcy says. "We would work evenings. We would quit at 10 p.m. I wasn't married, Paul wasn't married, we didn't have any kids. All we did was work on developing this technique. For eight years until 1995 we found nothing. Not a single planet."

Had this been a cheesy movie, this would have to be the obligatory montage scene: Marcy and Butler slaving away, stealing all the telescope time they could at Lick, refusing to give up. And then, just before the audience ran out of popcorn, the two would finally discover the first known exoplanet and be carried in triumph through the streets in an impromptu tickertape parade.

In reality, someone beat them to it. In 1995, a team from the University of Geneva came out of nowhere to announce that they'd discovered a planet orbiting the star 51 Pegasi. Convinced it was a mistake, Marcy and Butler spent the next four nights at Lick trying to debunk the claim. Instead, they confirmed it.

The ensuing media uproar, which many credit with helping renew public interest in life in space, and ensure NASA funding for astrobiology, only grew louder when Marcy and Butler proceeded to crank out evidence of ten more planets. For the previous eight years, they'd been so focused on honing their technique — and so unaware they had competitors — that they hadn't actually analyzed much of their data. A lot of it was sitting, unexamined, on hard disk. After 51 Pegasi, they finally combed through the data, finding proof of two more planets — around 70 Virginis and 47 Ursa Major — in a single month.


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