Astronomy_kc

The Big Bang
== The universe was created when an event called the Big Band occurred ;this event also caused galaxies to form. About 15 billion years ago the universe basically exploded out of nothing in less than a second. In the beginning the universe was very small and hot, but over time the universe began to cool down while it expanded. Once all the particles were at 3,000 degrees Kelvin electrons could start orbiting protons to create atoms. ==

== 2 billion years after the Big Bang galaxies started to form. Our galaxy (the Milky-Way) formed when the universe was about 3 billion years old. Collisions and merges were common between galaxies, but nowadays the galaxies are much further apart from each other. Galaxies start as a huge sphere of gas and then formed a spiral shape with a core (center.) There are many solar systems within our galaxy. ==

** The rotation of the Milky-Way Galaxy has many different orbits going on inside of it. The whole galaxy is turning, but each star and gas cloud is in its own orbit. When the four spiral arms of this galaxy spin matter piles up there. By the way the Milky-Way rotates we can tell that there is an invisible koruna containing 10 times the amount of matter we actually see. **

** There is a lot of history behind how the planets we know formed and how other things like moons, rings, and comets formed. The sun (a star) was formed by gravity pulling together gas and dust. Clumps of plantermples created in the sun's ring causing many big clumps of matter to be formed. 4 of the biggest clumps are now what we call Jupiter, Saturn, Uranus, and Neptune. In the inner solar system there were too many collisions so large masses couldn't form but smaller ones could. Then Mercury, Venus, Earth, and Mars were created out of those. **

== Moons, rings and comets were all created in a different way. The planets grew disks of there own where moons were created. The Moon was created in a catastrophic collision with Earth and another planet. Icy planatentles from the outer solar system became comets. Then rings were created by stray rocks and comets getting pulled in by planet gravitational pull. ==