It’s no secret that Alan Stern and other scientists who led the New Horizons mission were extremely dissatisfied with Pluto’s demotion from planet status in a 2006 general meeting 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 annoyed Pluto people have a plan. Stern and several colleagues have proposed a new definition for planethood. In technical terms, the proposal redefines planetship by saying, “A planet is a substellar mass body that has never undergone nuclear fusion and that has sufficient self-gravity to assume a spherical shape adequately described by a triaxial ellipsoid, regardless of orbital parameters. of it.” More simply, the definition can be formulated as “round objects in space that are smaller than stars”.
Here’s the problem with the new definition: Many solar system bodies fit the criteria. Pluto does, of course, but so do many moons, including ours around Earth. Dozens of objects have also been discovered in the Kuiper Belt, beyond Pluto’s orbit, that fit the definition. In fact, the number of “planets” under the new definition is now 110 and rising. (Obi-Wan Kenobi would also be right. The Death Star would indeed be no moon but rather also a planet.)
And what about the poor college students who have struggled to remember the eight planets of the solar system, with statements like “My college-educated mother just served us nachos?” Stern and his colleagues counter: “Certainly 110 planets is more than students can be expected to memorize, and indeed they shouldn’t.” They also bring up a good point, which is that students don’t learn science by memorizing things, but rather by understanding how things work.
“Understanding the natural organization of the solar system is much more informative than memorizing it,” the proposal states. “Teaching the zones of the solar system from the sun outward and the types of planets and small bodies in each may be the best approach.”