Pluto Not a Planet
CNN is reporting that the International Astronomical Union (IAU) has stripped Pluto of its planethood.
It has been a contentious week at the IAU's General Assembly in Prague. An initial proposal for a definition for the word planet would have kept Pluto and added at least three others. A counter proposal stripped Pluto of its title. After much debate, the IAU voted today.
Pluto will now be called a "dwarf planet" and Charon will remain its satellite. Other applicants for the title planet, Ceres and Xena will also be dwarf planets. Currently, only the other eight "classical" planets fill the requirements for the definition, “a celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a ... nearly round shape, and has cleared the neighborhood around its orbit.”
Image Credit: Dr. R. Albrecht, ESA/ESO Space Telescope European Coordinating Facility; NASA