Astronomers have discovered an unprecedented fifth planet orbiting a Sun-sized star. Located 41 light years from Earth, the star, dubbed 55 Cancri, is roughly the same size and age as our own Sun. Previously, they knew about four of the planets looping around it, but the latest find is particularly exciting. It's 45 times more massive than Earth, and about 72.5 million miles from its star. More exciting, though, is the fact that its existence implies that there could even be more planets nearby.