Pluto, Planet or Plan Not?

Since Pluto's discovery in 1930, there have been nine planets in the solar system, but a year ago, scientists at the California Institute of Technology said there were ten. An object they called Xena turned out to be bigger than Pluto and was also orbiting around the Sun. That set off an astronomical controversy that wasn't resolved until today, thanks to the International Astronomical Union. Planetary scientist Mike Brown led the Cal Tech Team that discovered Xena.