Digital Sprocket

Planet, dwarf planet, Plutoid… What a mess. I was fortunate enough to hear Dava Sobel speak shortly after Pluto’s initial demotion. She was part of the committee that was tasked with developing a definition for planet. Let’s just say that the formally announced definition was not what the committee recommended. Further more, over half the astronomers had left the convention before the definition came up for a vote. With a large number of scientists feeling left out, and disgruntled after the last debacle, it’s no real surprise that they are once more tackling this issue.

What is surprising is that the scientific community is not taking a scientific approach to labeling Pluto and other bodies in our solar system. Here’s what I mean. If you call Pluto a plutoid, it is a label that really only makes sense in our solar system. We are in the middle of a great hunt for extra solar planets. Let’s take a page from Launius and create a system to describe these bodies wherever we find them in the universe. A good system should describe both the origin of the body, and its relationship to the system in which is exists. Let’s take a stab at creating one such system.

First, if it’s round by it’s own gravity, let’s call it a planetoid. If not, we could call it an asteroidal body. How about composition? Is it mostly solid, liquid, or gaseous? We should probably add a tag line for with crust. We might want to describe the primary composition of the body as well. Is it mostly water, iron, methane, etc? We should also consider their size. Anything smaller than 3000km in diameter could be micro, while anything up to 20,000km is dwarf, bodies up to 80,000km are large, and over 80,000 is a giant. Thus the Earth might be a planetoid, iron liquid (with crust), dwarf body, while Mars is a planetoid, iron, solid, dwarf body. These could easily be abbreviated PILD, and PISD. The system is also useful, because as soon as you look at the descriptors for Mars and the Earth, it’s obvious that the two are similar, but not identical.

Next, we need to describe the relationship between our objects and their orbital system. If it orbits a star, it’s Solar centric. If it orbits a planetoid or asteroidal body, then it’s body centric. Next we have eccentric orbit vs. round orbit. Maybe we need to distinguish between highly eccentric like comets and more moderately eccentric. We should probably include a comment for objects that periodically change what body they orbit. I’m not sure it matters if they’ve “cleared their orbit” as it’s described in the planetary definition, but we can include a cleared or shared orbit. Then we also need to label how closely the body orbits its center. There are many ways we could do this. We could list the orbital period, or average orbital diameter. My initial proposition is that for solar centric bodies we break them down by inner, habitable, outer, and far outer zones. Others may disagree with that designator, but it’s a nice human-centric designator. So the Earth might be designated cleared orbit, habitable, solar centric body, or CHS for short.

Now that we have a meaningful system, when an astronomer speaks, his fellows will immediately and accurately know what he is talking about. If, at a conference, he proposes a new space telescope to search for extra solar PCHILDS, the other astronomers will nod their heads sagely, the media will complain that we need spend our money on P-children in this solar system, and the congressmen will ask if it can be built in their district.