1. Nebula: A star's life begins within a giant cloud of gas and dust called a nebula. Gravity pulls the particles together, causing the cloud to collapse.
2. Protostar: As the cloud collapses, the core heats up. When the core reaches a certain temperature and density, nuclear fusion begins. At this stage, the object is called a protostar.
3. Main Sequence: This is the longest stage of a star's life, lasting for billions of years. During this phase, the star fuses hydrogen into helium in its core, generating energy that creates outward pressure balancing the inward force of gravity.
4. Red Giant: When the hydrogen fuel in the core is exhausted, the star expands and cools, becoming a red giant. The star begins to fuse helium into carbon and oxygen in a shell around its core.
5. Post-Red Giant: Depending on the star's mass, different paths are taken.
* Low-mass stars: They shed their outer layers, leaving behind a dense, hot core called a white dwarf.
* Medium-mass stars: They may become unstable and pulsate as variable stars, eventually becoming planetary nebulae, with a white dwarf at the center.
* High-mass stars: They go through a supernova explosion, leaving behind a neutron star or, for the most massive stars, a black hole.
6. Remnant: The final stage of a star's life depends on its mass. The remnant could be a white dwarf, a neutron star, or a black hole.
This is a basic outline. The actual processes and stages are much more complex and can vary depending on the star's mass and composition.
