Two planetesimals collide during the early years of planet formation. Vast amounts of debris are blasted into space. NASA's...Read More >>Two planetesimals collide during the early years of planet formation. Vast amounts of debris are blasted into space. NASA's Spitzer Space Telescope found evidence that a massive collision of this sort occurred around Vega, a star about 25 light-years from Earth. Dust from such collisions now form a disc of dust orbiting Vega.The 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.
Vela molecular cloud, a cloud of dust and gas from which new solar systems may form. It lies about 3300 light years away from...Read More >>Vela molecular cloud, a cloud of dust and gas from which new solar systems may form. It lies about 3300 light years away from Earth.The 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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