A planet hunter powers down
After nearly a decade in orbit, more than half a million stars observed, and 2,662 planets discovered, the NASA space telescope Kepler has finally run out of fuel. Named after the 17th-century German astronomer Johannes Kepler, the probe was launched in 2009 to hunt for exoplanets—planets outside our solar system. It spent its first four years studying the same swath of space, during which time it helped astronomers establish that up to 50 percent of visible stars are likely have rocky, Earth-size planets that could potentially harbor alien life. After technical troubles forced engineers to alter Kepler’s mission, the telescope was tasked with examining new parts of the sky every few months. In total, the mission lasted twice as long as originally planned and dazzled astronomers with its finds, including worlds orbiting binary stars, inferno-like gas giants, and, last December, an eight-planet system. “Kepler has truly opened a new vista in astronomy,” William Borucki, a former mission leader, tells The New York Times. A planet-hunting Kepler replacement, the Transiting Exoplanet Survey Satellite, launched in April; another, the James Webb Space Telescope, is scheduled to go into orbit in 2021.