There's a 10th planet? When did this happen?

... and now they are just arguing about how big "UB313" is:

"LOS ANGELES - An icy ball discovered last year in the outer solar system is only slightly larger than Pluto, casting doubt on previous estimates that the so-called 10th planet was significantly larger, scientists reported Tuesday."

"The discovery of UB313, which Brown nicknamed Xena, reinvigorated the debate about what is considered a planet. Some astronomers have questioned whether Pluto should keep its planetary status, while others say UB313 should be the 10th planet because it is bigger than Pluto."

"If it is determined to be the 10th planet, UB313 would be the farthest-known body in the solar system." [more]

Update: everything you ever wanted to know about "2003 UB313" (its full name right now)