Pluto's Not a Planet so How Many Planets Are There?

Back in 1995, as Bill Clinton was gearing up to run for his second campaign and Bill Gates was about to release his new operating system, the first "exoplanet" was discovered. An exoplanet is a planet that exists outside our solar system. Since then, more than 400 such planets have been discovered in our galaxy, Bill Clinton has gone on to become the Secretary of State's husband, and Bill Gates and company are about to release a new operating system. (See The Washington Post story about "exoplanets." You can Google the two Bills, if you really want to.)