The solar system has only eight planets, and Pluto isn’t one of them. That’s the official word from the International Astronomical Union (IAU). On Aug. 24, astronomers at an IAU meeting in Prague, Czech Republic, voted overwhelmingly to demote Pluto from planet to “dwarf planet.” In doing so, the astronomers also approved the first-ever definition of a planet.
Log in
Subscribers, enter your e-mail address for full access to the Science News archives and digital editions.