* A protostar is a dense core of gas and dust that is gravitationally collapsing.

* As the protostar collapses, it heats up and begins to emit light.

* This stage can last for several million years.

2. Main Sequence

* The main sequence is the longest and most stable stage of a star's life.

* During this stage, the star burns hydrogen in its core.

* The temperature and luminosity of the star remain relatively constant.

* The length of the main sequence stage depends on the mass of the star.

3. Post main Sequence Evolution

* When a star exhausts the hydrogen fuel in its core, it begins to evolve off the main sequence.

* The star's core contracts and heats up, while its outer layers expand and cool.

* This stage can lead to a variety of different outcomes, including:

* Red Giant: The star becomes a red giant, a large, cool star with a low surface temperature.

* White Dwarf: The star collapses into a white dwarf, a dense, hot remnant of a star.

* Neutron Star: The star collapses into a neutron star, a very dense object made up of neutrons.

* Black Hole: The star collapses into a black hole, a region of space with such strong gravity that nothing, not even light, can escape.