According to the Big Bang theory, the universe began as an extremely hot and dense point known as a singularity, approximately 13.8 billion years ago. As the universe expanded and cooled, matter and energy started to separate and form various structures.
The formation of the solar system, however, is a separate process that occurred much later within the universe's timeline. It is thought to have occurred about 4.6 billion years ago through a process known as stellar nucleosynthesis and planetary accretion. Here's a brief overview of the formation of the solar system according to the prevailing scientific model:
Stellar Nucleosynthesis: Prior to the formation of our solar system, there were earlier generations of stars that formed and eventually ended their lives in supernova explosions. These supernovae released heavy elements and enriched interstellar space with elements beyond hydrogen and helium, such as carbon, oxygen, and iron.
Protostellar Disk Formation: A nearby supernova explosion or a shockwave from a passing star may have triggered the collapse of a region within a molecular cloud, causing it to contract under the influence of gravity. As the cloud collapsed, it began to spin, forming a rotating disk called a protostellar disk or a protoplanetary disk.
Condensation and Accretion: Within the protostellar disk, the central concentration of matter gave rise to a protostar, which became the Sun. The disk itself consisted of gas, dust, and other solid particles. These particles began to collide and stick together through a process called accretion, gradually growing larger over time.
Planetesimal Formation: Accretion continued, leading to the formation of planetesimals—small bodies ranging from centimeters to kilometers in size. These planetesimals further collided and accumulated more matter, eventually becoming protoplanets.
Planetary Formation: Through continued collisions and gravitational interactions, protoplanets continued to grow, attracting surrounding material and forming larger bodies. The protoplanets went through a process called planetary differentiation, in which denser materials sank to the core while lighter materials formed the outer layers.
Clearing the Nebular Disk: Over millions of years, the protoplanets interacted with the remaining gas and dust in the protostellar disk. The gravitational influence of the protoplanets caused the gas and dust to either be accreted by the growing planets or be pushed away, clearing the disk.
Formation of the Solar System: Eventually, the remaining protoplanets in the disk settled into stable orbits around the Sun, forming the planets, moons, asteroids, and comets that make up our solar system today.
It's important to note that while this is the prevailing model for solar system formation, ongoing research and observations continue to refine our understanding of this process.