Introduction

Ever wonder how the solar system was created? Or maybe what it was like billions of millions of years ago? Scientists find the answers to these questions and more by studying things that fall to earth from space. These objects gives us clues to help us understand the solar system.

The solar system began as a big cloud of rotating dust called the solar nebula. The solar nebular collapsed under its own gravity. Some scientists believe this was triggered by a near supernova, which is an exploding star. As the solar nebula collapsed, it flattened out into a disk-like shape. While the dust particles rotated around in this disk-like shape, they kept smashing into each other forming larger and larger bodies. Eventually, they got big enough to form moons, the asteroid belt, the icy comets beyond Pluto, and the planets.

When the cloud of dust collapsed, most of the material was pulled toward the center. Soon the pressure became so great that nuclear reactions started and the Sun let out its first beams of light. Then, the Sun started to produce solar winds (gases that flow continuously from the Sun.) On the inner part of the disk, the wind was so strong that it blew away most of the lighter materials. In the outer regions the wind was not as strong and only blew a little bit of the lighter materials away. That is why the outer planets; Jupiter, Saturn, Uranus, and Neptune are gaseous planets. They contain the lighter materials that were blown away from the sun by the solar winds. The inner planets; Mercury, Venus, Earth and Mars are small rocky planets because they contain the heavier materials that were not blown away by the solar winds.

The inner planets in the solar system are smaller than the outer planets. This is because the outer planets are made of gaseous materials which were more plentiful in the solar nebula than the heavier materials that formed the inner planets. There was less of the heavier materials in the nebula which accounts for the inner planet’s small size. The four inner planets are very similar in their material make up and their size. They are mostly made of iron and rock. The outer planets, except for Pluto, consist of hydrogen and helium. Their chemical make up is more like the Sun’s than the inner planets. They are larger and have thick atmospheres. Pluto has been consider the ninth planet ever since its discovery in the 1930s. It varies so much from the other planets that some astronomers do not refer to it as a planet. Pluto is manly of ice because it is so far away from the sun.

Every planet, except for Mercury and Venus, has at least one moon. The inner planets have very few moons. The moons were at first, separate bodies that came together. Earth has one moon. Mars has two moons. The outer planets, except Pluto, have so many moons that they look like mini solar systems. Jupiter has 16 moons. Saturn has the most moons with 18. Uranus has 17 moons. Neptune has 8 moons. Pluto only has 1 moon.

Most of the material that was in the solar nebula was used to form the Sun, the planets, and their moons. However, there was still some debris leftover. The leftover debris became the asteroid belt between the orbits of Mars and Jupiter or formed the icy comets that are beyond Pluto.

The asteroid belt still has enough debris to form a tenth planet. All planets started out as separate bodies that eventually, hit each other and became one big body. This planet would be half the size of the moon. Jupiter’s gravitational pull, however, keeps this debris from forming into a planet. Little pieces from the asteroid belt, called meteorites, break off and sometimes hit earth. Scientist use these fallen meteorites to get valuable information on the beginnings of our solar system.

The comets beyond the orbit of Pluto form an icy cloud. If our solar system was disturbed by the gravitational pull of another star it could also upset the orbit of this cloud of comets. The disruption of the cloud could send millions of comets flying towards the Earth. A direct hit by one of these comets would be fatal to life on Earth.

The Sun will not last forever. Once the Sun uses up all its hydrogen gas, it will start burning the helium gas that remains. The Sun will swell up into a red giant star. It will reach out as far as Venus’ orbit and could expand as far as Earth’s orbit. After the Sun uses up all of its helium gas, it will collapse with an enormous explosion. The debris will fly out into space to help form new solar systems, starting the whole system over again.