In space, there are large clouds of gas and dust called nebulas (or nebulae). These are the beginnings of stars and planets. Nebulas are held together by gravity, though the force is very weak. In response to the gravity, pressure from inside the cloud created by moving particles pushes against gravity, balancing the two forces. This way, gravity doesn't crush the nebula, and the collection of gas and dust can maintain its cloud form.
However, the balance can be upset by two nebulas colliding or a nearby star exploding. These events compress the nebula even further, making it so dense that it collapses on itself due to gravity, causing the temperature to increase and becoming the perfect place for the birth of stars. It's now known as a solar nebula, or a nebula that forms stars and planets.
However, the balance can be upset by two nebulas colliding or a nearby star exploding. These events compress the nebula even further, making it so dense that it collapses on itself due to gravity, causing the temperature to increase and becoming the perfect place for the birth of stars. It's now known as a solar nebula, or a nebula that forms stars and planets.
When the solar nebula collapses, it begins to rotate, becoming hotter and denser at its center. As it rotates, the gas and dust rotating around the center begin to form a disk, which cools enough for dust particles to form. These particles then collide and form larger particles; as this process continues, the particles grow to the size of boulders and asteroids. These new small bodies are known as planetesimals. Their size depends on their distance from the center of the solar nebula.
The planetesimals continue to increase in size until their gravity is strong enough to pull solid matter near their orbit. They continue to grow through this method and become large enough to be called protoplanets. They then become large enough to form planets or moons through the same process. The spherical shape of these solar bodies is due to the fact that a sphere is the only geometric form where all points on the surface are an equal distance from the center. And that's how planets, just like the ones in our solar system, form.
The planetesimals continue to increase in size until their gravity is strong enough to pull solid matter near their orbit. They continue to grow through this method and become large enough to be called protoplanets. They then become large enough to form planets or moons through the same process. The spherical shape of these solar bodies is due to the fact that a sphere is the only geometric form where all points on the surface are an equal distance from the center. And that's how planets, just like the ones in our solar system, form.