Astronomers have revealed new evidence that there are not just one but four tiny planets circling around Barnard's Star, the second-nearest star system to Earth. The four planets, each only about 20 to 30% the mass of Earth, are so close to their home star that they zip around the entire star in a matter of days. That probably means they are too hot to be habitable, but the find is a new benchmark for discovering smaller planets around nearby stars. "It's a really exciting find -- Barnard's Star is our cosmic neighbor, and yet we know so little about...