As Earth orbits the sun, it exerts a gravitational pull that makes the sun “wobble” to and fro at a rate of up to nine centimeters per second. This so-called radial velocity variation is what astronomers often measure to find exoplanets. Yet their instruments are only sensitive enough to turn up large exoplanets—some of them many times more massive than Jupiter—that can exert a tug of more than one meter per second. A group of researchers at Germany's Max Planck Institute for Quantum Optics has developed a calibration technique using a device called a laser-frequency comb to make radial velocity searches more sensitive. It will make it easier to find smaller, potentially Earth-like planets that may be hospitable to life.

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