The solar system form was formed about 4.5 billion years ago from a massive cloud. The massive cloud contained hydrogen, helium, and pinches of heavier elements such as oxygen, carbon, nitrogen, silicon, and iron. The materials in the massive cloud clumped together and the largest clump became a prostar. Compression of the prostar due to gravity caused the fusion of hydrogen into helium. This gave birth to the sun. In the inner hotter regions of the cloud, heavier elements of dust grains came together to form Mercury, Venus, Earth and Mars. In colder regions away from sun, frozen water, methane, and ammonia came together so quickly that their gravities attracted the nearby hydrogen and helium gases. These gases became the main ingredients in Jupiter, Saturn, Uranus, and Neptune.
Is there a tenth planet in our solar system?

Astronomers who search the outer reaches of the solar system have located many small cometary bodies in the once-theoretical Kuiper Belt. One of these new objects is considered as a "planet". Its official designation is 2003UB313, and astronomers who discovered it nicknamed it Xena. Xena is 20 percent larger than Pluto and has a small moon.

What is an astronomical unit?

One astronomical unit (AU) is the average distance from the center of the earth to the center of the moon. It is 149,597,870 km.

What is an asteroid belt?

An asteroid belt is a zone between the orbits of Mars and Jupiter. As the gravity of nearby Jupiter kept pulling the asteroids in the asteroid belt apart, they never formed a planet.

Does life exist on other planets in our solar system?

Except on the earth, no other planets or moons in our solar systems have living systems. Saturn's moon, Titan and the Jupiter's atmosphere have a soup of organic molecules, amino acids and proteins in a pre-biotic state. But life has not been detected anywhere other than earth.

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