Now researchers at the Harvard-Smithsonian Center for Astrophysics have adapted a relatively young laser technology to discern the once undetectably faint gravitational influence such planets exert on their home stars' light output.

Their system increases the precision of spectrographs--optics used to analyze light from distant stars--by a hundred times, and it should make it possible to detect Earth-like planets. Large planets, called hot Jupiters because of their resemblance to the one in our solar system, can affect the motion of their stars by tens of centimeters per second. But the effects of small planets like Earth on the motions of their stars are much more subtle, on the order of a centimeter per second, and the shifts in wavelength are correspondingly tiny. "Current techniques have reached a wall at one meter per second,"

Walsworth says that it will still be a few years before new Earth-like planets are detected using this technique. His group is currently adapting the frequency-comb system for transport from Massachusetts to Arizona, where it will be used to calibrate the spectrograph at the Multiple Mirror Telescope. In 2010, the system will be installed on a state-of-the-art spectrograph in the Canary Islands. "The ultimate goal is to find planets of Earth mass with a one-year period around a Sun-like star," says Walsworth. But he notes that the first discoveries using the new system will be rocky planets orbiting more closely to dimmer, cooler stars.

But until now, no one has been able to figure out how to adapt this technology for astronomy: the fringes of light in an unmodified optical-frequency comb are too closely spaced together. To solve this problem, Walsworth and Li coupled an optical-frequency comb with a filtering chamber called a Fabry-Pérot cavity that uses a series of mirrors to cancel out most of the fringes.

Apparently a key stumbling block is that they can't get started because nobody can figure out how the hell to pronounce "Fabry-Pérot". I feel their pain.