List the steps of the nebular theory of Solar System formation

List the steps of the nebular theory of Solar System formation

1. planetesimals begin to form in a disk
2. protoplanetary disk forms
3. some planetesimals grow into protoplanets by incorporating other solid materials into their orbits
4. differentiation occurs when a protoplanet has grown to a diameter to at least 400 km
5. some protoplanets are able to clear orbits of other debris and become planets.

The correct answer and explanation is :

Steps of the Nebular Theory of Solar System Formation

1. A nebula collapses – A vast cloud of gas and dust (solar nebula) collapses due to gravity, possibly triggered by a nearby supernova or other external forces.
2. A protostar forms – The center of the collapsing nebula accumulates mass and heats up, forming a protostar (early Sun).
3. A protoplanetary disk forms – Surrounding gas and dust flatten into a rotating disk around the protostar.
4. Planetesimals begin to form in the disk – Small solid particles collide and stick together, gradually forming planetesimals (objects a few kilometers in size).
5. Some planetesimals grow into protoplanets by incorporating other solid materials into their orbits – Through accretion, some planetesimals continue to grow by gathering nearby dust and smaller objects.
6. Differentiation occurs when a protoplanet has grown to a diameter of at least 400 km – The internal structure of the protoplanet starts to differentiate into a core, mantle, and crust as heavy materials sink and lighter materials rise.
7. Some protoplanets are able to clear orbits of other debris and become planets – The largest protoplanets continue growing, eventually dominating their orbits and becoming planets.

Explanation

The Nebular Theory explains how the Solar System formed about 4.6 billion years ago from a massive cloud of gas and dust. As this nebula collapsed under gravity, it spun and flattened into a protoplanetary disk, with the forming Sun at its center. Small dust grains within the disk stuck together, creating planetesimals, the building blocks of planets. Over time, planetesimals merged to form protoplanets, growing larger by accreting more material.

When protoplanets reached a diameter of at least 400 km, internal heat caused differentiation, with heavy elements (like iron and nickel) sinking to form cores while lighter elements formed the crust. The largest protoplanets cleared their orbits of debris, officially becoming planets. This process led to the formation of the eight planets we see today, along with moons, asteroids, and other celestial bodies.