* Gravitational Collapse: While a single dust particle has a tiny gravitational pull, a giant cloud of dust and gas collectively has a significant gravitational force. If the cloud is dense enough, its own gravity begins to pull the particles towards each other.
* Accretion: As particles clump together, they gain mass, increasing their gravitational pull. This attracts even more particles, leading to a snowball effect of growth.
* Core Formation: Over time, the center of the cloud becomes increasingly dense and hot due to the collisions of particles. This eventually forms a core, the foundation of a planet or star.
* Further Accretion: The core continues to attract and collect more material, eventually sweeping up the remaining dust and gas in the cloud.
In the case of stars:
* The core of a star eventually becomes so hot and dense that nuclear fusion begins, where hydrogen atoms fuse to form helium, releasing tremendous energy. This energy provides the outward pressure that balances the inward gravitational pull, creating a stable star.
In the case of planets:
* Planets don't undergo nuclear fusion. They simply continue to accrete material until they reach a certain size and mass. This accretion can be influenced by the gravitational forces of nearby stars and other planets.
It's important to note:
* The process of star and planet formation can take millions or even billions of years.
* The presence of other forces, like magnetic fields, can influence the process.
* The initial cloud of dust and gas is not uniform. Areas of higher density and different composition contribute to the variety of celestial bodies that form.
In short, while individual particles have weak gravity, the collective gravity of a massive cloud of dust and gas is enough to overcome the initial outward pressure, triggering the process of accretion that eventually leads to the formation of stars, planets, and other celestial bodies.
