It is a huge understatement to say that there has been some controversy about how astronomers have handled the status of Pluto and the definition of a planet in recent years. The 2006 decision by the International Astronomical Union that defined a planet and created the new term "dwarf planet" confused and angered some members of the general public. Many astronomers were not pleased either.
It has been two years and the controversy has not gone away. It is manifesting itself this week in the form of The Great Planet Debate. Astronomers Mark Sykes, director of the Planetary Science Institute, and Neil deGrasse Tyson, director of the American Museum of Natural History, will square off on Thursday, August 14 from 1:30 to 2:45 p.m. (PDT) in a debate that will be carried live over the Internet. To watch the event you must register online in advance.
Sykes is proposing that our solar system has 13 planets (Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Charon, Eris, and Makemake), while Tyson, as you might imagine has a different idea (just 8 planets like the IAU put forward). No matter which side of the debate you come in on, this is an interesting time where people can see how the scientific process moves along and how new discoveries can make us re-think our ideas.