Stages in the Development of Stars and Planets

Formation of Protostar
- The process begins with a dense region within a giant molecular cloud collapsing under its gravity.
- As the cloud collapses, it forms a protostar, a hot core that will eventually become a star.
- The protostar is surrounded by a rotating disk of gas and dust.

Birth of a Star
- The protostar continues to gather more mass from the surrounding disk.
- When the core temperature reaches millions of degrees, nuclear fusion ignites, and the protostar becomes a main-sequence star.
- The star begins to shine and emit light and heat.

Formation of Planetary System
- Within the protoplanetary disk surrounding the star, dust grains collide and stick together to form planetesimals.
- These planetesimals further collide and accrete to form protoplanets.
- Over time, these protoplanets evolve into planets, moons, asteroids, and other celestial bodies.

Evolution of Stars and Planets
- Stars continue to fuse hydrogen into helium in their cores, releasing energy in the form of light and heat.
- Planets undergo various processes such as differentiation, geological activity, and atmospheric evolution.
- Both stars and planets evolve over millions or billions of years, influenced by factors like mass, composition, and environment.

Conclusion
The development of stars and planets is a complex and fascinating process that involves the interplay of gravity, nuclear fusion, and various physical and chemical interactions. From the formation of protostars to the evolution of planetary systems, each stage contributes to the diversity and beauty of the universe.