It was only a decade ago that astronomers confirmed that there are planets around other stars. Since then, nearly two hundred extra-solar planets—or exoplanets—have been identified. Most are giant balls of gas, like Jupiter, that would not support life as we know it. But within the next decade, Matthews predicts, “we will find an Earth-like planet.” That discovery will likely be made using a method he and his team are pioneering at the University of British Columbia. “To point to a star and say, “That star has a planet around it that is about the mass of the Earth and is in an orbit at which liquid water could exist,’” he says, lowering his index finger to his face. “You only need to find one of those.”
Matthews’ bus arrives and the stocky planet hunter squeezes aboard among the throng of clerks, students, and other commuters. Sporting a black T-shirt and blue jeans, he looks more like an aging roadie than a rocket scientist. But Matthews is leading the only team in the world currently capable of discovering an Earth-like planet. His crew operates a small satellite telescope launched by the Canadian Space Agency in 2003. In just three years, the tiny spacecraft—dubbed most (Microvariability and Oscillations of STars)—has overturned much of what astronomers thought they knew about stars and solar systems.
most is about to get some competition. In October, a French-led consortium plans to deploy a similar satellite telescope called corot. And the Americans intend to launch a much larger planet-hunting spacecraft called Kepler in the fall of 2008. These are just the first among a half-dozen serious planet-hunting missions in the works, part of an international adventure the likes of which this planet has not witnessed since the era of Magellan and Drake: a race to determine whether or not we are alone in the universe.
“And so there are innumerable suns, and likewise an infinite number of earths circling about those suns, just like the seven near to us which we see circling about the sun.” —Giordano Bruno, De l’infinito universo et Mondi (1584)
Four centuries ago, attempts to expand our knowledge of the universe could be met with charges of heresy. Astronomer and philosopher Giordano Bruno, an advocate of the Copernican solar system, was burned at the stake by the Roman Inquisition, for example. But by the time Matthews launched most, a Life magazine poll had found that 54 percent of respondents believed intelligent life exists on other planets, 30 percent thought aliens had already visited Earth, and 1 percent claimed to have met an extraterrestrial. “A good fragment of the population believes The X-Files was a documentary series,” Matthews chuckles.
The bus lurches into traffic. Its windows are so splattered with mud and grime that streetlights are difficult to see clearly—mosquitoes would be impossibly so. Likewise, the Earth’s rich atmosphere, which makes this little blue planet so hospitable, makes it impossible for Earth-based astronomers to “see” planets outside this solar system. But while exoplanets cannot be seen, they can be detected indirectly. Because stars are affected by the gravity of other objects, they will wobble if a planet is nearby. Measure the wobble accurately, and you can infer the mass of the planet, as well as the size and shape of its orbit.
Astronomers began looking for wobbles in the mid-twentieth century, attaching cameras to the first generation of large refracting telescopes and arduously plotting the small movements of nearby stars. In 1963, prominent American astronomer Peter van de Kamp announced that he’d discovered a planet orbiting Barnard’s Star. Van de Kamp’s claim appeared credible, and his discovery was hailed in the media. But later scrutiny found problems with his results, and his peers concluded that it was not yet possible to track star position with sufficient precision to find planets.
A new approach emerged in the 1970s. As a star wobbles toward or away from its observer, the light it emits shifts slightly to the blue and red ends of the spectrum, respectively. Armed with this knowledge, Canadian astronomers Bruce Campbell and Gordon Walker fitted a telescope with a tube of hydrogen fluoride gas (used to measure tiny changes in wavelengths), creating an interstellar spectrometer. In 1982, after tests at the Dominion Observatory in Victoria, they took their big tube of poisonous gas to the Canada-France-Hawaii Telescope on the summit of the Mauna Kea volcano. There they began monitoring twenty-three nearby stars.
Campbell and Walker’s technique “called the precision radial-velocity method” soon detected what appeared to be several large planets. But within a few years, the astronmers realized that the stars they were observing were far more turbulent than the sun. They were simply detecting movement within the stars themselves. By 1992, the only star they were still fairly certain was under the sway of a planet was Gamma Cephei, relatively close by at only 52 light years away. Seeking to avoid the kind of embarrassment that befell van de Kamp, Campbell and Walker published a paper in the fall of 1992 with the circumspect title, “Gamma Cephei: rotation or planetary companion”
