The search for Earthlike, habitable planets beyond the Sun has been something like a boulder rolling downhill ever since the Kepler space telescope went into orbit in 2009. Before that, ground-based astronomers had been finding so-called exoplanets one or two at a time, here and there in the cosmos, and pretty much all of them were far too large to be hospitable, or much close to the fires of their parent stars, or, usually, both. -snip- Nobody quite imagined what the Kepler team has just announced, however. Writing in Nature, William Borucki, Kepler’s principal scientist, along with dozens of collaborators,...