Summary: In 2006, the International Astronomical Union decided on new definition of a planet--and Pluto didn't make the grade. It was bumped down to "dwarf planet" status. But it's not alone. It's now one of five known dwarf planets in the solar system. One of them, called Ceres, may hold clues to how life formed on Earth. In this podcast, we talked to planetary scientist Mark Sykes about this tiny world. Podcast produced by David Levin. Original interview by Susan K. Lewis. NOVA is produced by WGBH in Boston. Funding for NOVA is provided by ExxonMobil, David H. Koch, the Howard Hughes Medical Institute, the Corporation for Public Broadcasting, and public television viewers. To learn more, go to pbs.org/nova/pluto
