Pluto: No Longer a Dwarf, But Still Not a Planet

Pluto and its satellite, Charon, in happier times. Image credit: Dr. R. Albrecht, ESA/ESO Space Telescope European Coordinating Facility; NASA.

It looks like it is time to revise those astronomy textbooks once again. For the second time in as many years, the world’s astronomers have reclassified Pluto. The International Astronomical Union has issued a statement saying that small bodies such as Pluto would be known by a new name: plutoid.

Two years ago, the IAU sparked a major controversy by reclassifying the distance world as a dwarf planet. The decision seemed especially upsetting to many schoolchildren, who identify with the tiny world that hovered forever on the periphery of a Solar System populated by much larger, grown up planets.

Whether this latest decision will mollify or mystify children is yet to be seen. However, it doesn’t really remove the confusion over why the IAU just didn’t leave well enough alone two years ago. Pluto orbits the sun, has an atmosphere, and possesses three satellite (including one, Charon, that’s half its size). In other words, it seems to fit most people’s definition of a planet. Why the change?

What was really confusing, however, was why astronomers would tempt fate by demoting a planet named after the Roman god of the underworld. One assumes they’re not very superstitious. Otherwise, they might be a tad worried that Pluto will exact his revenge on them, if not in this life then definitely in the next.