Planetesimals

Hypothetical solid celestial body that accumulated during the last stages of accretionAccumulation of smaller objects into progressively larger bodies in the solar nebula leading to the eventual formation of asteroids, planetesimals and planets. The earliest accretion of the smallest particles was due to Van der Waals and electromagnetic forces. Further accretion continued by relatively low-velocity collisions of smaller bodies in the. These bodies, from ~1-100 km in size, formed in the early solar systemThe Sun and set of objects orbiting around it including planets and their moons and rings, asteroids, comets, and meteoroids. by accretion of dust (rock) and ice (if present) in the central plane of the solar nebulaThe primitive gas and dust cloud around the Sun from which planetary materials formed.. Most planetesimals accreted to planets, but many – such as the asteroids– never combined to form large bodies. The very largest asteroids can be considered protoplanets.

Bodies ranging in size from a few meters to a few hundred kilometers that accreted early in solar-system history.