REVIEW: Solar System Formation (BrainPop)

The solar system can be divided into two areas, inner and outer. The solar system started out as a cloud of gas (the nebula disk). Matter closer to the Sun in the nebula disk was warm enough to boil away most of the gases and ices, leaving only rocky material behind. Gravity brought the rocky material together over time and that formed the inner planets.

The inner planets (Mercury, Venus, Earth and Mars) are made up of solid, rocky material. The planets tend to be smaller (in comparison to outer planets). They have warmer temperatures, which is vital for our planet to sustain life. While the exact reasons the inner planets formed this way is unknown, scientists have a theory.

The outer planets (Jupiter, Saturn, Uranus and Neptune) are also known as gas giants. These planets are larger than the inner planets, but are made primarily of gases and ices. As the name "gas giant" might suggest, the outer planets are largely made up of different kinds of gasses, such as methane or ammonia. The temperature on the outer planets is far cooler than the inner planets as well; therefore, ices of various compositions are also a major component of the outer planets.

Scientists believe that the outer planets formed in the less-dense outer reaches of the nebula disk, where temperatures were cooler. The gas was too far from the Sun to be boiled away, and the cooler temperatures allowed ice to form. Additionally, some matter escaped the inner solar system to make it farther out. This matter is lighter elements such as oxygen. As a result, small cores of ice and rock formed. Gravity caused the ice, gas and heavier elements that make up the planets'cores to collide and begin to compress together. The result was the formation of the outer planets.

The following video explains how the sun & planets in our solar system formed.

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