Johnny has to learn a new mnemonic, Planet Definition Committee about to make studying a little harder.

The International Astronomical Union may have to tell children to stop using “My Very Easy Method Just Showed Us Nine Planets” as a technique to memorize the planets. If the Planet Definition Committee’s proposal is accepted those same kids may have to learn something the length of The Canterbury Tales.

A group of seven individuals comprised of astronomers, writers and historians have presented the IAU with a unanimous consensus for a proposed new definition of the word “planet”. The word originally comes from the Greek word for “wanderer”; the new definition just has people wondering.

For an object to gain the status of planethood it must meet two conditions. First, the object must orbit a star, but may not be a star itself. Second, the object must be massive enough to have become rounded as a result of its own gravity.

If this new definition stands up then the addition of at least three more planets will be included in our solar system. From there the floodgates could open. Astronomer Mike Brown of CalTech has labeled the newly proposed definition as “leave no ice ball behind.” Brown actually has a vested interest in the new definition. He was part of the team credited with discovering the object beyond Pluto’s orbit, Xena, “the tenth planet”; its scientific name has been recognized as 2003 UB313. Dismissing the discovery of a new planet would be difficult Brown admitted “but I’d get over it.” According to Brown the new definition could lead to over fifty new planets.

With the new definition proposed, two classes of planets are possible.

The “classic planets” consist of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. These eight will be known simply as planets.

Left off the list is Pluto which would fall into the same class as Xena, and Charon (Pluto’s large moon, slightly smaller than Pluto itself). This class would be labeled as “plutons.” Plutons reside in orbits around the Sun that take longer than 200 years to complete. Plutons typically have orbits that are highly tilted, they have orbits that are far from being perfectly circular, and they are considerably smaller than “classic planets.”

Fear not fans of Pluto, plutons are still considered planets. 

The 12th object to be recognized as a planet would be Ceres. Located in the asteroid belt between Mars and Jupiter, Ceres enjoyed planet status when it was discovered in 1801. Several decades’ later astronomers had compiled a growing list of objects similar to Ceres. Instead of granting them planet status, Ceres was demoted to an asteroid. It has been called a “dwarf planet” because it is smaller than Mercury, but a planet nonetheless. 

Astronomers are to vote on the proposal next week.