Sciency Words: Ploonets

Sciency Words: (proper noun) a special series here on Planet Pailly focusing on the definitions and etymologies of science or science-related terms.  Today’s Sciency Word is:


If you’ve ever played Super Planet Crash (cool game, highly recommended, click here), then you know how difficult it is to maintain a stable orbit.  The planets just keep pulling each other this way and that.  It’s gravitational chaos!  Fortunately, Super Planet Crasher doesn’t include moons.  I imagine the game would be way harder if it did.

Recent research (click here) gives us a better idea of what happens to moons that get yanked out of their proper, moonly orbits.  According to computer simulations, many destabilized moons will crash into their planets.  A few will crash into the sun or be hurled out of the solar system entirely.  But a surprisingly large number—almost half of them—will settle into new orbits around their suns, becoming planets in their own right.

The scientists behind this research have proposed a new term for these runaway moons.  They want to call them “ploonets.”  And furthermore, they describe four different kinds of ploonet we might find out there.

  • Outer ploonet: a ploonet orbiting beyond the orbit of its original planet.
  • Inner ploonet: a ploonet orbiting inside the orbit of its original planet.
  • Crossing ploonet: a ploonet that crossed the orbit of its original planet.
  • Nearby ploonet: a ploonet that shares almost the same orbital path as its original planet.

We may even be able to confirm the existence of ploonets in the near future.  All we have to do it look toward so-called “hot Juipters”—Jupiter-like planets that have migrated dangerously close to their suns.  If those computer simulations are correct, hot Jupiters should have shed small, icy ploonets all over the place during their migratory journeys.

I think we can all agree ploonet is an adorable word, but is this actually a useful term for astronomers and astrophysicists?  I’m not sure.  I guess it depends.  How important is it, do you think, to make a distinction between planets that were always planets and planets that used to be moons?