Astronomers recently declared that Xena, the object known as 2003 UB313, is bigger than Pluto — over 400 miles in diameter larger. Xena was originally discovered by Mike Brown, a professor of planetary science at the California Institute of Technology, but no one has been able to confirm his original speculation that the object is bigger than Pluto until just recently. Due to the object’s irregular orbit, ocassionally Xena’s orbit is three times as far from the sun than that of Pluto.
The International Astronomical Union is still in heated debate on whether or not Xena is even a planet. The group’s definition, which is currently being re-evaluated, could leave us with either eight planets (omitting Pluto), or expand it to 10 planets.