Dec 22, 2009
Current estimates put the age of the solar system at 4.5 billion years. There have been several theories advanced, over time, as to the origin of the solar system. The most widely accepted theory today is called the "modified nebular hypothesis." It claims that the solar system was formed from an immense cloud of gas and dust (a nebula). Gravity and rotational forces caused the cloud to flatten into a disc.
Much of the cloud's mass drifted into the center and became the sun. The left over parts of the cloud formed small bodies called planetesimals. These planetesimals collided with each other, gradually forming larger and larger bodies, some of which became the planets. This process is thought to have taken about 25 million years.
Sources: Moore, Patrick. Atlas of the Solar System, pp. 10-11; Van Andel, Tjeerd H. New Views On an Old Planet, p. 28.
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