Pick your favorite image of an extraterrestrial. Perhaps it's a stumpy green guy with red eyes and purple antennae. Maybe it's that sleek alien with a huge forehead and black eyes that earthlings put on bumper stickers and key chains. It could be Jabba the Hut or Marvin the Martian. Doesn't matter. Imagine he's sitting on, say, the third rock from some star 30 light-years away (the distance of 7 trillion marathons) and peering at the light from our own sun through a powerful telescope. The question is: Can he see us?
No, no and no. He cannot see us. To him, the sun is just a pinprick of light, and the Earth and its eight fellow planets are too dim and too close to our star to resolve. The kind of vision needed to see us would be equivalent to us being able to see someone on Neptune drop a quarter; our green friend Marvin would need a telescope the size of his solar system to actually see the Earth.
So the fact that Berkeley, Calif., astronomer Geoffrey Marcy has been able to detect planets around other stars is, simply, amazing -- both as a technological feat for modern earthlings and as a cosmological double take. Scientists once assumed Earth was a unique locus for life in the universe, but the more planets Marcy finds, the more likely it seems that there are real extraterrestrials out there sitting on them. Forget the science fiction; they may soon be fact.
Marcy isn't the only astronomer finding "extrasolar" planets -- as planets orbiting other stars are called -- nor did he announce the first discovery. A Swiss team scooped him on the first one in 1995. But since then, he's been racking up planets like Mark McGwire racks up homers -- except there's no Sammy Sosa to threaten his lead. His gangbusters team has the credit for two-thirds of the planets found (19 of 29 at last count) and the only known system of planets -- the three giants orbiting Upsilon Andromedae, which they announced last April.
With his boyish eyes and ruler-straight nose, Marcy needs a goatee to help him look older than his graduate students. He is only 45 -- young for a scientist at the top of his game. He talks about extrasolar planets with an energy and clarity not unlike Carl Sagan's. Astronomers don't appreciate that comparison; they think Sagan sold out the field with overwrought predictions and reflexive self-aggrandizing. Marcy is more humble -- always making sure the team gets credit. He is also contributing more to astronomical knowledge than Sagan did with his suppositions. And Marcy isn't a missionary for the cosmos the way Sagan was; he simply has a passion for planets. So he's in the right job; he's the study of a man well fulfilled.
And of a man well vindicated. There are two hot pursuits in astronomy these days. One is figuring out the fate of the universe -- a hand-waving mix of supernovae, equations and guesswork pronouncements. Will it expand or collapse? Where is the dark matter, or is it dark energy? The other is the question of life beyond our planet.
In 1982, Marcy left the University of California at Santa Cruz with a Ph.D. in astrophysics and took a postdoctorate position studying the magnetic properties of stars. Mindful of the need for advancement in academia, he published papers such as "The Magnetic Field on the Late-Type Dwarf Xi Bootis A," in respectable if dry scientific journals. But he wasn't happy. The work was good for the career, but bad for the soul.
He had fallen in love with the universe as a 14-year-old boy when his parents bought a telescope. "It vanished into his room immediately," Marcy's mother says, "and the only sign we had that he was alive was that his alarm would go off at 2 in the morning, and he would go outside and look up at Saturn or something." Marcy recalls these nights, too. He loved Saturn and its rings and its moon Titan; he spent months charting Titan's orbit around the planet.
Star magnetism had no such draw for him, and he found himself moping through his postdoc years in chronic depression. "I was wondering whether I could continue as a research astronomer," he recalls. "I had to find some work in astrophysics that appealed to me on a gut human level. I asked myself, What would appeal to me even if I wasn't an astronomer?"
One morning, he stood in the shower for 45 minutes, wondering if he should quit, when the answer came to him in the form of a question: Is there life elsewhere in the universe? Are there other worlds out there, sites for biochemistry and biology? He decided to go find some planets.
That was 1983, the year that NBC aired "V," a miniseries about alien lizards that come to Earth to eat us, and the year after Steven Spielberg gave us E.T. and his magic finger. Life beyond our solar system was great entertainment, but it was lousy science. Marcy's pursuit of planets didn't win him a grand appointment. He landed a job at San Francisco State University, a school with no special reputation for astronomy. He remembers telling people at cocktail parties that he was looking for planets around distant stars. Some laughed, some looked at their shoes and some -- this being California -- thought it was a groovy idea.
His colleagues were less enthusiastic. One night at the Lick Observatory, in the hills east of San Jose, he ate dinner with the other astronomers sharing telescope time that evening. He told them he was looking for planets. One choked and expectorated to keep from laughing. The rest returned to their boiled broccoli and their legitimate academic conversation. To the scientists, extrasolar planets were an open question; they didn't have the public's sense that looking for planets was like looking for debris at Roswell. But they knew that they couldn't see someone drop a quarter on Neptune, and they knew that Marcy would never see a planet around another star.
If Marcy was insulted, he wasn't daunted. The promise of finding a planet had all the gee-whiz factor a scientist could ask for, enough to keep him on task for 12 years without a payout. And the work was hard. He had to make his astronomical instruments 1,000 times more sensitive than those his colleagues were using.
Think back to Marvin the alien on his planet 30 light-years away. He's looking at the sun, and for the sake of simplicity imagine that the only planet around our sun is Jupiter, the massive gaseous giant, 318 times the size of our little rock. He can see the star (our sun), but he can't make out Jupiter. So his challenge -- like Marcy's -- is to find a convincing but indirect way of proving that Jupiter exists.
Gravity connects Jupiter to the sun. Jupiter travels around the sun because the sun is much larger: Its huge gravitational pull keeps the planet sailing around it. But Jupiter has a gravitational pull, too, and it exerts a force on the sun. The sun doesn't move much, but it does lean slightly toward Jupiter as the planet revolves. Our alien astronomer 30 light-years away cannot see the planet, but maybe he can see the sun move a bit.
That's exactly what Marcy has done. He developed a technique to catch stars leaning toward their planets as the planets revolve. Marcy calls this motion a "wobble," and he uses the light coming from the star to detect it.
It works like this: When an ambulance passes you on the street, the pitch of its siren changes; it's pitched higher when it's coming toward you and lower when it's moving away. This Doppler-shift phenomenon happens because the sound waves bunch up against each other like a compressed Slinky on the approach, and then spread out like an extended Slinky on the retreat. Light waves do the same thing. So as our sun wobbles because of Jupiter's pull, it moves toward our alien Marvin some of the time, and away from him some of the time -- ever so slightly. If Marvin has a light analyzer as sensitive as the one Marcy uses, he'll be able to pick up that back-
In late 1995, Marcy was scooped by Michel Mayor, a Swiss scientist who used the same technique of looking for the Doppler shift and found the first confirmed extrasolar planet, orbiting a star called 51 Pegasi in the constellation Pegasus. Marcy and his colleagues started racing through their own amassed data -- they had been collecting light from stars for years while they worked on their analyzing software. When they crunched the numbers, they saw evidence of several planets -- they could have been first. Nevertheless, Marcy's years of persistence collecting light and improving his instruments quickly set him ahead. He announced two planets in early 1996, giving him two out of three on the planet chart. Four years later, he still holds the lead with the same ratio and no chance of being overtaken.
Most of the astrophysics community accepted the wobble-
Marcy's friends and advisors remember how much trouble academic colleagues gave him in the '80s, but today no astronomer seems to recall deriding him for his work. That would be a tough thing to admit these days, similar to a biologist forswearing evolution. Marcy's planets have essentially shifted the focus of astronomy, and astronomy has rewarded him. This summer, the University of California at Berkeley appointed him the head of its new Center for Integrative Planetary Studies, an interdisciplinary group of chemists, biologists, physicists and astronomers combining their efforts to look for life beyond our solar system.
Marcy doesn't gloat, and he hasn't slowed down. Throughout his apotheosis, he has kept his eye on the technique and on the data, determined to keep finding planets. Since he knows the planets' appeal on a "gut human level," he is conscientious about making himself accessible to the public. Through the most recent announcement of the planet dimming the star (which many reports misconstrued as "photographic" evidence of a planet), Marcy answered so many press calls that he didn't eat until 11 at night for days on end.
But that's OK, says Marcy's wife, Susan Kegley, a chemist who works for Pesticide Action Network in Berkeley: He's happy. "He has kept that childlike wonder of his science -- the curiosity that put him on the roof at the age of 14 with his little telescope," Kegley says. "He just loves it; to him, it's play."
Stay tuned for more results of Geoff Marcy's play. He promises more solar systems soon, and more attention to smaller Earth-like rock planets, which are harder to find than huge gas giants like Jupiter.
Rocks are of special interest. They're where the little green men should be.