Good News! Pluto Might Be A Planet Again.
Were you, like me, bummed when back in 2006 when the International Astronomical Union decided that Pluto wasn't a planet? Well, fear not! We may be getting our favorite tiny celestial entity back as one of the official "planets". Maybe.
Originally, Pluto was booted because there appeared to be a bunch of other big rocks just like Pluto in the same general vicinity, and they're all considered too small to be called a planet.
But, not everyone was willing to accept that.
Harvard science historian Owen Gingerich, who chairs the IAU planet definition committee, said at a forum last month that "a planet is a culturally defined word that changes over time," and he also said that Pluto is, in fact, a planet. (I like this guy.)
Unfortunately for those of us who are team "Pluto IS A Planet), another expert named Gareth Williams, who is the associate director of the IAU's Minor Planet Center, said that Pluto is not a planet. He tried to back that up by using the official definition. That definition states that a planet is a celestial body that:
• is in orbit around the Sun,
• is round or nearly round, and
• has "cleared the neighborhood" around its orbit, which means it is not surrounded by objects of similar size and characteristics.
This Williams guy says that Pluto failed when it comes to that third bullet point, because it has several other "dwarf planets" near it and also sometimes overlaps Neptune's orbit. (Whatever. What does that guy know?)
Sure, Pluto is kind of small. It only has a radius of about 750 miles, which is about one-firth of the size of the Earth's radius. But... good planets come in small packages? Or something?
The debate between the two guys mentioned above and a guy named Dimitar Sasselov, who is the director of the Harvard Origins of Life Initiative, took place on September 18. Two out of the three (Gingerich and Sasselov) said that Pluto should be a planet and the audience voted, and the majority of them agreed.
Unfortunately, that wasn't an official vote. So the debate continues.