What is the process behind star formation?

Star formation is a process where dense parts of molecular clouds collapse under gravity, forming a protostar that eventually becomes a star.

Star formation begins in molecular clouds, which are dense regions of gas and dust in space. These clouds are primarily composed of hydrogen molecules, along with helium and trace amounts of heavier elements. When a part of this cloud becomes particularly dense, it begins to collapse under its own gravity. This collapse forms a hot, dense core known as a protostar.

As the protostar continues to gather mass from the surrounding cloud, its temperature and pressure increase. This process is known as accretion. The protostar remains in this stage for around 100,000 years. During this time, it is not yet hot enough for nuclear fusion to occur, but it emits light due to the heat generated by the gravitational collapse.

Eventually, the core of the protostar becomes hot and dense enough for nuclear fusion to begin. This is the process where hydrogen atoms combine to form helium, releasing a large amount of energy in the process. This energy creates an outward pressure that balances the inward pull of gravity, preventing further collapse of the star. This stage marks the birth of a new star.

The star will remain in this stable state, known as the main sequence, for several billion years. During this time, it will continue to burn hydrogen in its core, producing light and heat. The star's size, colour, and temperature during the main sequence depend on its mass. Larger stars are hotter and bluer, while smaller stars are cooler and redder.

After the star has exhausted its hydrogen fuel, it will undergo various stages of evolution, which may include expansion into a red giant, collapse into a white dwarf, or explosion as a supernova, depending on its initial mass. This marks the end of the star's life cycle, but the material expelled in these final stages can contribute to the formation of new stars, continuing the cycle of star formation.