Astronomers Find a Near-Earth-Size Planet in the Habitable Zone of a Very Sunlike Star

One of the biggest goals in the search for exoplanets--alien worlds--is finding an Earth-size planet orbiting its star in the "habitable zone," where liquid water might exist on its surface. In other words, finding another Earth. So far, a dozen such planets have been found. All of those planets may be very much like Earth (we can't be sure, as I'll get to in a sec), but they orbit smaller, cooler stars than our Sun. On Thursday, astronomers announced they have found another planet in its star's...