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.
To study this far-off solar system, astronomers have been using a technique that measures the gravitational tug planets exert on the local star. The trick is that this planet-hunting method doesn't work as well when you're looking for smaller, Earth-sized worlds, since the gravitational tug they'd exert would be tinier. (For an explanation of the other popular search method, see the video here.) The group thinks 55 Cancri might have smaller planets in its system. We just haven't seen them yet.—Gregory Mone
(Image credit: NASA/CalTech)