[firebaze]

Despite reading quite a lot about astronomy, comets and asteroids and the history of all of the three, I didn't get the distinction between asteroids and comets yet. I understand the composition makes the difference, but I didn't get why we expect exactly two (!) distinct categories of intersolar/interstellar objects, and giving them exactly two distinct names. Why not more, or less (i.e. no distinction at all, just a summary of the probable composition)?

Why is this so? Is there a fundamental reason to make this special distinction, or is it just "tradition"?

[AnimalMuppet]

Asteroids mostly have circular orbits. Comets (at least the ones we see) tend to have very highly eliptical orbits. That I think is the origin of the distinction.

But asteroids also tend to be at lower distances from the sun than comets. That in turn leads to them tending to be composed more of rocky material, whereas comets have more ice.

I am not an astronomer, so any and all details may be in error. Corrections are welcome.

[garmaine]

Mostly tradition. Asteroids have had their volatiles baked off their surface, or never had them due to forming inside the frost line. But it’s not a very intrinsically meaningful distinction—it’s more about what they look like from the vantage point of Earth as they come by on close approach.