Back in 2006, Pluto was demoted from planet to dwarf planet. That was a strange shock, personally speaking. I was still in college, and I’d grown up with a nine planet Solar System. Hearing that some council somewhere had decided to reduce the count to eight sounded ridiculous, though time’s drain has since made that fact rather irrelevant.
Pluto not being a “true planet” holds no bearing on, say, paying my mortgage or making sure my kid does his homework (why do kindergartners have homework!?).
Still, it matters greatly in the scientific community, and firmly defining the nature of planets and extraterrestrial objects that float about the void is crucial to further exploration and discovery. Now, scientists have a proposal to make Pluto a planet again.
Alan Stern, principal investigator of NASA’s New Horizons mission to Pluto, has formed a team charged with redefining what makes a planet a planet. Here’s the genuine definition from their proposal (which you can see sourced at the base of this post).
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.
Below that scientific definition is one that the proposal suggests would be appropriate for, say, elementary school kids. Planets would be “round objects in space that are smaller than stars.”
Under this definition, there would be 110 planets in the Solar System
That’s not me looking up and counting. That’s what the proposal says. They also argue that kids and lay folk would be just fine only learning a few of the planets rather than all of them. Here’s that full bit.
Certainly 110 planets is more than students should be expected to memorize, and indeed they ought not. Instead, students should learn only a few (9? 12? 25?) planets of interest. For an analogy, there are 88 official constellations and ~94 naturally occurring elements, yet most people are content to learn only a few. So it should be with planets
They make a good point. What do you think? Anything round and smaller than a star suited to be a planet sound good to you? Me? Sure, scientists, sounds good.