1. A SOLAR SYSTEM IS BORN
Chapter 16 – 1
Part 1

2. The Solar Nebula
Just like clouds in the sky, there are clouds in space.
These clouds are called nebulas.
They are made mostly hydrogen and helium and dust.

3. Gravity Pulls Matter Together
The matter of a nebula is held together by gravity.
There is a lot of empty space between the particles in the nebulas.
So the gravity is very weak.

4. Pressure Pushes Matter Apart
Gravity causes the particles in a nebula to be attracted to each other.
As particles move closer together, collisions cause pressure to increase and particles are pushed apart.
If the inward force of gravity is balanced by outward pressure, the nebula becomes stable.

5. Upsetting the Balance
The balance can be upset if two nebulas collide or if a nearby star explodes.
As the matter collapses inward, the temperature increases and stars begin to form.
This is a solar nebula.
Our sun formed like
this.

6. How the Solar System Formed
The solar nebula collapses and begins to spin.
The rotating cloud gets hotter and denser in the middle.
The outer edges of the disk begins to cool.
Dust particles collide and form larger particles.

7. From Planetesimals to Planets
The collision of particles formed bodies called planetesimals.
Their size continues to increase because gravity keeps pulling in material.
All suns, planets and moons are a sphere.
A sphere is that shape because all points on the surface are an equal distance from center.

8. THE END