Astronomers Find 2 Giant Exoplanets Locked in an Endless Dance

The two newest planets spied by the Kepler space telescope are locked in a forever back-and-forth. When Kepler's scientists saw a star 2,000 light years away dim slightly, they knew there was the chance it was the telltale signature of a planet passing in front. But when the calculations were done and the confirmation came in, they found a surprise—what they'd seen was actually two planets transiting in front of the star. NASA says it's the first time they've ever caught such a sight, and today the scientists officially announced the finding with a study in Science. While other studies have found multiple planets around a single star--in fact, it happened earlier this week--those studies have used different planet-detection techniques like the wobble method. The two worlds, both gas giants, do more than orbit the same star on the same plane, though. They push and pull each other in a motion that keeps the two exoplanets close to arithmetic celestial perfection. Kepler-9B, the larger, orbits the star in 19.24 days on average, the astronomers saw. Kepler-9c, the smaller, completes a revolution in an average of 38.91 days. But every time the scientists checked, 9b's orbit was getting 4 minutes longer, while 9c's shrank by 39 minutes.