The possible existence of Planet Nine, first broached in January, has become a hot topic of speculation. Just last week, one tabloid announced that comets perturbed (pulled out of their orbits) by Planet Nine would soon lead to the demise of life on Earth! (Astronomer Phil Plait ran an amusing rebuttal in the New Scientist.) But is there actually a Planet Nine?

Recall, an Astronomical Unit (AU) is the distance from Earth to the Sun. From the Sun to Neptune, the farthest known planet, is 30 AU. Pluto is but one of a thousand balls of ice orbiting between 30 and 50 AU.

But in 2003, Mike Brown and his team at the California Institute of Technology, or Caltech as it is usually known, found a body they named Sedna whose orbit comes no closer to the Sun than 76 AU, and which actually arcs out to nearly 1000 AU. It is hard to imagine how it could have been formed out there; more likely it was pushed there by the gravity of some other planetoid.