Stages in the Development of Stars and Planets
The development of stars and planets is a complex process that involves several stages. Here are the key stages explained in detail:

1. Star Formation:
- Stars are formed from clouds of gas and dust called nebulae.
- Gravitational forces cause the nebula to collapse and form a protostar.
- As the protostar continues to contract, its core temperature increases, eventually leading to nuclear fusion and the birth of a star.

2. Main Sequence Stage:
- Once nuclear fusion begins, the star enters the main sequence stage.
- During this stage, the star fuses hydrogen into helium, releasing energy in the form of light and heat.
- This stage can last for billions of years, depending on the size of the star.

3. Planetary Formation:
- Planets are formed from leftover gas and dust in the protoplanetary disk surrounding the star.
- Small particles collide and stick together, forming planetesimals that eventually grow into planets.
- The composition and size of the planets depend on their distance from the star and the materials available in the disk.

4. Planetary Evolution:
- Planets undergo various processes such as differentiation, where heavier materials sink to the core, and lighter materials form the crust.
- They also experience geological activity, such as volcanism and tectonic movements, shaping their surface and internal structure.
- Over time, planets can also interact with other celestial bodies, leading to changes in their orbits and environments.
In conclusion, the development of stars and planets is a fascinating journey that involves intricate processes and interactions between various celestial bodies. Each stage plays a crucial role in shaping the universe as we know it today.