An asteroid is a randomly created celestial body with sizes between 20 and 30 meters. It is going to be released in version 23.10.
This is the first type of celestial body that is not on rails to change their orbits. This means that they can be captured by other bodies or collide with them. The current Kerbol System is designed to prevent any SOI change which would disturb their orbit. Unlike the other celestial bodies, asteroids are too light to have any gravity. This makes them more like a non-player created craft.
Asteroids should not be confused with captured asteroids, as they are on rails and have gravity.
NASA asteroid capture
Along with asteroids, an official mod will be released which is a mission to tug an asteroid into Kerbin orbit to investigate it. To allow this, the asteroids need to be lightweight and not on rails, to allow the orbit to be altered.
- “KSP-TV: Squadcast, back and later than ever!” interview of HarvesteR by Maxmaps (19:40)