This is a schematic showing the forming solar system.
Click on image for full size
C. Alexander
How the Solar System may have formed out of the Primordial Nebula
The solar system contracted, or shrank together, out of a spinning cloud of hydrogen and helium gas. This spinning cloud had a certain amount of momentum, which caused it to flatten, somewhat the way a ball of pizza dough can be made flat by spinning it in the air. As it flattened, the gaseous material was forced to begin condensing into solid form.
These little particles of solid material were soft and sticky, and further clumped together to form larger balls of solid material whenever they touched each other, somewhat the way "silly putty" does. Eventually only a few large clumps of this material remained in the forming solar system, and they became the core of "protoplanets".
For a diagram showing what kind of materials condensed where in the forming solar system, click here.
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