Dust grains form within a protoplanetary disk because:
A) binary accretion begins.
B) the interstellar cloud collapses and heats up.
C) gas accretes onto large protoplanets, clearing out the medium.
D) the disk cools through radiation.

Question

Quizplus · Accepted Answer

Dust grains form within a protoplanetary disk because the disk cools through radiation, allowing atoms and molecules to come together and form dust particles. This process is called condensation, and it is the first step in the formation of planets. Gas and dust in the disk can then continue to accrete onto these particles, gradually building up larger and larger bodies.

Dust Grains Form Within a Protoplanetary Disk Because