Stellar Evolution

The stellar evolution cycle is the evolutionary process by which stars themselves change over time. This process is somewhat laid out on Hertzsprung-Russell Diagrams but this section serves to go more into depth on the processes occurring throughout the evolutionary cycle.

However, it is important to note that stellar evolution is not linear. This means that not every star follows the exact same evolutionary process in its lifetime.

This makes the process of stellar evolution very intriguing because there are multiple ways for stars to proceed in their lifetimes.

Here are the pages for this section:

Protostar

T-Tauri Stars

Main-Sequence Stars

Giant Stars

Planetary Nebulae

Supernovae

White Dwarfs

Neutron Stars

Black Holes

The formation of stars is quite simple. Stars form from molecular clouds themselves due to two main factors: density and temperature. The centers of molecular clouds are very cold, as the atoms within them have little to no kinetic energy, on average. Remember that the temperature of a system is mainly just a measure of the average kinetic energy of that system. However, molecular clouds are also extremely dense, with extremely high densities. These two factors are essential in star formation. The density of molecular clouds means that their inward forces of self-gravity towards their cores are extremely strong. The low temperature however means that the cloud doesn't have much outward thermal pressure counteracting gravity. This causes gravity to dominate and form large clumps which eventually lead to stars.