EVERYDAY SCIENCE

Detailed explanation-1: -A protoplanetary disk is a rotating circumstellar disk of dense gas surrounding a young newly formed star, i.e. a TTS. If the disk is massive enough, the runaway accretions begin resulting in the rapid-100, 000–300, 000 years-formation of Moon-to Mars-sized planetary embryos.

Detailed explanation-2: -Planetary system The nebular hypothesis of solar system formation describes how protoplanetary disks are thought to evolve into planetary systems. Electrostatic and gravitational interactions may cause the dust and ice grains in the disk to accrete into planetesimals.

Detailed explanation-3: -The solar nebula was the rotating, flattened disk of gas and dust from which the solar system originated  4.6 Ga ago (Figure 1).

Detailed explanation-4: -Our Sun has several circumstellar discs: the asteroid belt, the Kuiper belt and the Oort cloud.

Detailed explanation-5: -Wikipedia: The Kuiper belt is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune (at 30 AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger-20 times as wide and 20 to 200 times as massive.