Most astronomers believe that all the members of the solar system, from the giant Sun to the smallest asteroid, were born out of a vast, spinning cloud of gas and dust – the solar nebula. The process began 5 billion years ago with the formation of the Sun.
The planets and other objects formed from unused material. When the solar system was nearly complete, 500 million years later, just 0.0002 percent of the solar nebula’s original mass remained.
The planets began to form about 4.6 billion years ago. Astronomers think that each of the major planets came together from an initial, ring – shaped mass of material around the Sun.
As the planets formed, tiny particles stuck together to make grain – sized lumps, then pebbles and boulders, and eventually larger bodies called planetesimals.
Originally posted: November 16, 2012