EVERYDAY SCIENCE

Detailed explanation-1: -Protoplanetary disks are formed almost immediately after the collapse of a molecular cloud. As material further from the protostar with higher angular momentum begins to fall inward, the material will quickly flatten into a disk that surrounds a protostar.

Detailed explanation-2: -The material in the disks is thought to consist mainly of gas (99% by mass), predominantly molecular hydrogen and helium with trace amounts of CO and other molecules, and small dust particles (1% by mass).

Detailed explanation-3: -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-4: -The planets Mercury, Venus, Earth, and Mars, are called terrestrial because they have a compact, rocky surface like Earth’s terra firma. The terrestrial planets are the four innermost planets in the solar system.