Quote:
Originally Posted by mr_sir  I can understand classifying rocks as moons if they orbit a planet, but how do they decide if something that orbits a star is actually a planet? It must be a pretty hard thing to classify. |
Um, that's what this discussion is all about.
Quote:
Originally Posted by Chimaera182 mr_sir: if a mass had life on it, it wouldn't change its classification. The presence of life doesn't change whether a planetary body is a planet or a moon... The guidelines are based on the physical make-up of the "rock" itself... |
That's not correct. The previous guidelines that dealt strictly with an object's physical characteritics (namely, having enough mass to make it round) never settled the question of whether Pluto or other Kuiper Belt objects should be called "planets". Under the old guidelines, even some of the moons out there were big enough to be called "planets". That was the whole problem. The new guidelines also include the stipulation that a "planet" is an object that "has cleared the neighborhood around its orbit". That has nothing to do with the physical make-up of the "rock" itself.
The way I read it, we're also talking about the
location of the "rock" and its proximity to neighboring bodies, since only "rocks" that were lucky enough to be close enough to the sun to end up by themselves in their own "neighborhoods" can qualify as "planets". (For some reason, moons don't count as "neighbors".)