NASA/JHUAPL/SwRI

It's no secret that Alan Stern and other scientists who led the New Horizons mission were extremely displeased by Pluto's demotion from planet status in 2006 during a general assembly of the International Astronomical Union. They felt the IAU decision undermined the scientific and public value of their dramatic flyby mission to the former ninth planet of the Solar System.

But now the positively peeved Pluto people have a plan. Stern and several colleagues have proposed a new definition for planethood, which they intend to submit for consideration at the next general assembly of the IAU. The final arbiters of astronomical definitions will next gather in Vienna in August 2018.

In technical terms, the proposal redefines planethood by saying, "A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters." More simply, the definition can be stated as, “round objects in space that are smaller than stars."

Here's the thing about the new definition—a lot of bodies in the Solar System meet the criteria. Pluto does, of course, but so do many moons, including our own around Earth. There are also dozens of objects discovered in the Kuiper Belt, beyond Pluto's orbit, that meet the definition. In fact, the tally of "planets" under the new definition is now 110 and rising. (Also, Obi-Wan Kenobi would be proven correct. The Death Star would indeed be no moon but rather a planet, too.)

And what of the poor students who have struggled to memorize the eight planets of the Solar System, with sayings such as "My Very Educated Mother Just Served Us Nachos?" Stern and his colleagues counter: "Certainly 110 planets is more than students should be expected to memorize, and indeed they ought not." They also raise a good point, notably that students don't learn science by memorizing things but rather understanding how things work.

"Understanding the natural organization of the Solar System is much more informative than rote memorization," the proposal states. "Teaching the zones of the Solar System from the Sun outward and the types of planets and small bodies in each is perhaps the best approach."