[In Depth] Kepler enlists relativity to find planets
Back in business after a heart-stopping near-shutdown in April, NASA's Kepler space telescope is about to begin an 80-day campaign to search for exoplanets using a novel technique. Called gravitational microlensing, it's based on Einstein's discovery that gravity bends light. That means massive objects in space can act as lenses, focusing the light from objects even farther from Earth. Astronomers have found many cases in which galaxies distort the images of quasars. Microlensing works on a much smaller scale: Individual stars or planets focus the light of more distant stars, making the background star appear to grow brighter and then dim again. By measuring those rising and falling "light curves," Kepler will give astronomers valuable information about planets orbiting other stars—including exoplanets in far-out orbits that other techniques can't detect—and even free-floating planets that don't orbit stars at all. Author: Daniel Clery