Legacy Astronomical Images > Miscellaneous Series > Protoplanetary Disks Unit
A protoplanetary disk is formed when an interstellar gas cloud begins to contract or collapse under the force of gravity. The cloud then begins to rotate rapidly and flatten into a disk due to the conservation of angular momentum. This rotating disk may break up into many smaller condensations which form asteroids or protoplanets. The protoplanets then grow into full-size planets by attracting more material from the surrounding interstellar medium.