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Solar System

Evolution of the Solar System

Two planetesimals collideTwo planetesimals collideThe Solar System has not stayed the same since its formation, but evolved—changed over time. In its early years, the giant planets shifted their positions, moving nearer or farther away from the Sun. This "planetary migration", particularly that of Jupiter, was responsible for much of the Solar System's early evolution. This is because the giant planets' massive gravitational force caused all other objects near them, including even some other planets, to be sent flying in all directions. Objects have also been colliding with one another continually since the Solar System's formation, often bringing about great changes. The Sun's gradually increasing output of energy has had an effect on the inner planets, and will continue to do so.


A molecular cloud, from which solar systems may formA molecular cloud, from which solar systems may formThe Solar System began to form about 5 billion years ago when a giant cloud of dust and gas, called a molecular cloud, began to fall in on itself under its own gravity. This collapse may have been triggered by shock waves from a supernova. The cloud became a swirling disc, known as a solar nebula. The centre of the disc, hotter and denser than the rest, began to bulge, forming the beginnings of a star, called a protostar. This eventually became our Sun. The planets, moons, asteroids and a myriad of other small objects all formed from the material that made up the remainder of the disc.

The idea that the Solar System was formed from a nebula—a cloud of dust and gas—was first developed by the German philosopher Immanuel Kant and published in his "Universal Natural History and Theory of the Heavens" in 1755.

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