Tuesday in the journal Nature, NASA announced the discovery of Kepler-20e and Kepler-20f, two exoplanets -- planets outside the Solar System -- that are about the size of Earth and orbit a star similar to the sun.
"This is a most important milestone," Francois Fressin, the lead author of the paper describing the planets, told HuffPost. "It demonstrates for the first time that Earth-sized planets exist around other stars, and secondly that we are now able to detect them."
Scientists detected the new planets using data from the Kepler spacecraft, a space telescope with a mission to "search for habitable planets."
