astronomy_mfh

=From Big Bang to Galaxies= Our Universe began to form about 15billion years ago and exploded out of nothing starting the Big Bang Theory. The Universe began hot and packed to a size smaller than the nucleus of an atom, but within a fraction of a second the Universe started expanding and matter was created. After one second the temperature had fallen 10billion degrees. At 3minutes protons and neutrons started developing Helium nuclei. For a long time after that the Universe didn’t do much except expand and drop in temperature. Once it was able to reach 3000K atoms started to form.

=Formation of Galaxies= 2billion years after the beginning of the Universe, galaxies began forming taking on a sponge-like structure. Our galaxy, the Milky Way Galaxy, didn’t start forming until 3 billion years after the Big Bang. And it started out as nothing more than a huge sphere of gas. Galaxies are made up of billions of stars and are huge! =The Milky Way Galaxy= There are many galaxies out in space, but the one we live in is known as the Milky Way Galaxy. The galaxies are huge! To get from one side to another it would take about 100,000 light years and is 2,000 light years think. In the middle there is a central disk, which is about 20,000 light years across. In this central bulge there are many of the weaker stars, like the orange, yellow and red stars. It is believed that in the center is a huge black hole. The galaxies are filled with stars that shine brightly, and the dark spots are dust clouds. Our galaxy is huge and it is filled with many stars and planets!

=Rotation of the Galaxy= The Milky Way galaxy revolves, just as all of the other galaxies do, but galaxies revolve differently than most things. The Milky Way has four spiral arms that extend out from the central bulge turning with the galaxy. The whole galaxy turns, but it isn’t smoothly. Each star cluster is in its own orbit. It takes our sun 250years to travel around the galaxy once, even though it is moving at 250Km per second. The rotation of galaxies can tell you what surrounds it. We think that a huge invisible corona is surrounding ours. Our galaxy could be much bigger than it appears to be. =The History of the Solar System=

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The solar system is made up of eight planets that revolve around one giant star, the sun. The sun has a huge disk surrounding it, made of gasses and dust. Four of the planets are known as the Giant Planets, which are Jupiter, Saturn, Uranus and Neptune that formed in the outer Solar System. The four soon grew their own disks and soon moons formed. All of these planets were massive enough to hold onto an atmosphere. The other four are known as Terrestrial Planets that formed in the Inner Solar system. These planets are Earth, Mars, Venus and Mercury and are smaller because they number of collisions was very high. The Terrestrial Planets went through many collisions, keeping it warmer. All of the metal in the planets went down into the middle while all of the lighter substances, such as dirt, rose to the top.====== =Formation of Moons, Rings, and Comets=

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In space there are many rings, comets and moons. The moon that revolves around the Earth was believed to have been the result of a collision between the Earth and another planet the size of Mars, leaving Earth a pretty big moon compared to the other planets. The craters on the moon are a result of many collisions for millions of years. The moons for other planets are planetessimals, which are large solids that have collected to become larger and larger. They can become larger by colliding, but sometimes when they collide they break apart. Comets are the result of icy planetessimals that make their way up to the warmer part of space, near the sun. The heat starts to melt them and pushes back on them, creating the tail. Rings surrounding the larger planets are most likely the leftover planetessimals or comets that have been ripped into smaller parts due to the gravity of the large planets. The Solar system has been around for a long time filled with planetessimals, planets and stars.======

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