In the Beginning: Formation of the Solar System
4.5 billion years ago
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The Milky Way galaxy
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It's believed that the solar system was formed when something, possibly the shock of an exploding star or a stellar cloud collision, disturbed an enormous cloud containing dust and cold gas, and compressed it until it collapsed inward from the force of gravity.
This big squeeze created the Solar Nebula, a giant cloud of material that is believed to have spawned our solar system. As the Nebula collapsed, its temperature and rotation increased. The increased spin began to flatten the nebula, pressing atoms and molecules together into particles. The hottest point, right at the center, became the Sun. Cooler particles spread to the outer regions and eventually formed planets and moons.
Meteors are thought to be pieces left over from the formation of the solar system and some meteorites have been dated at 4.5 billion years old.
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