Using NASA's Spitzer Space Telescope, astronomers have confirmed that Earth's nearest known rocky exoplanet neighbor is HD 219134b at just 21 light-years away. "Most of the known planets are hundreds of light-years away. This one is practically a next-door neighbor," said astronomer and study co-author Lars A. Buchhave of the Harvard-Smithsonian Center for Astrophysics. The super-Earth is too close to its star, HD 21913, to sustain life which it orbits around in three days.