HarvesteR

An asteroid is a randomly created celestial body usually in orbit around Kerbol or Dres. Asteroids appear and disappear frequently so that there are always a few scattered around the vicinity of Kerbin. Asteroids first appeared in the game with the release of the Asteroid Redirect Mission update, or 0.23.5.

Asteroids can be found and monitored via the tracking station and come in various sizes, ranging from class A (at most 3 meters across and weighing tens of tons) to class E (at least 30 meters across and weighing thousands of tons). Their coloration ranges from light to dark grey, with patches of black and white dispersed over the surface.

Unlike the true celestial bodies in the game, asteroids are fully under control of the physics system. They can be rotated or accelerated by the application of torque or thrust, and moved into a different orbit or another body's sphere of influence with correct maneuvering. They do not have SOIs of their own or produce gravity to affect nearby objects; they may not be landed on by craft, stood on by kerbals on EVA, or have flags planted on them, but may be docked with through the use of the Advanced Grabbing Unit.

Asteroids are procedurally generated; each new one is a unique shape and size. The part configuration file used as a prototype for each procedurally-generated asteroid can be found in GameData/Squad/Parts/Misc/PotatoRoid/part.cfg. It is a C class asteroid that can be attached to any spacecraft after editing the part's config file, allowing it to be under any part category entered.

Some celestial bodies such as Gilly are often referred to as captured asteroids; this is merely an astronomical classification as they are not fundamentally different from the larger moons and planets in the way that asteroids are.