What are two reasons why the terrestrial planets formed closer to the Sun after the supernova event that initiated the formation of the solar system?

The formation of the terrestrial planets closer to the Sun in our solar system is attributed to the conditions and processes that followed the supernova event. Two key reasons are:

Temperature Gradient in the Protoplanetary Disk:

After the supernova explosion, a rotating disk of gas and dust, known as a protoplanetary disk, formed around the young Sun. This disk had a temperature gradient, with higher temperatures closer to the Sun. As a result, solid particles in the inner regions were more likely to be composed of refractory materials (substances with high melting points) that could condense and solidify in the hotter environment. This favored the formation of solid rocky bodies, leading to the development of the terrestrial planets (Mercury, Venus, Earth, and Mars) closer to the Sun.

Accretion and Clearing of Inner Disk:

The inner regions of the protoplanetary disk experienced higher temperatures and stronger solar winds. This created conditions where the solar wind and radiation pressure could efficiently sweep away lighter volatile materials, such as hydrogen and helium. The terrestrial planets formed through a process of accretion, where small planetesimals collided and stuck together to form larger bodies. The clearing of volatiles in the inner regions allowed the terrestrial planets to accrete and retain primarily rocky materials, contributing to their composition as dense, rocky bodies.

These factors combined to favor the formation of the terrestrial planets closer to the Sun, while the outer regions of the protoplanetary disk, being colder and with a higher abundance of volatiles, favored the formation of gas giants like Jupiter and Saturn.