Here's why:
* Gravitational Collapse: The collapse of the nebula was initiated by gravity. The densest part of the nebula, which contained the most mass, started attracting more material towards it.
* Nuclear Fusion: As the material in this dense core compressed, the temperature and pressure increased dramatically. Eventually, the conditions were hot and dense enough to trigger nuclear fusion, where hydrogen atoms fused into helium, releasing immense energy. This is what marks the birth of a star, in this case, our Sun.
So, the Sun was the first object to form, and its immense gravity continued to attract the remaining material in the nebula, eventually leading to the formation of the planets, moons, asteroids, and other objects in our solar system.
