If Jennifer Aniston's ring seems depressingly huge to you, maybe you could use a little perspective. For example, that rock is nothing compared to the planet discovered recently that is twice the size of earth but "made largely out of diamond." Reuters reports that a "U.S.-Franco" team of astronomers estimate that at least a third of 55 Cancri e's mass, the equivalent of about three Earth masses, could be diamond. And it's only 40 light years away. Unfortunately, “it is also incredibly hot” — 3,900 degrees or so.