Stars

A star is a giant glowing ball of gas that is held together by its enormous gravity. Stars run on nuclear fusion and create enough heat and light we can see them from thousands of light-years away. If a star did not run on nuclear fusion there would be no outward force to hold the star in a shape and the star would collapse. A star starts out as a big cloud of dust that is held together by gravity and these baby stars are called protostars. These protostars create nuclear fission which then evolves into nuclear fusion and a full fledged star is formed. A star spends approximately 90% of its time in what is called the main sequence which is the stage our sun is in now.

Here is a star in its main sequence. http://aspire.cosmic-ray.org/labs/star_life/images/sun2.jpg

After billions of years at this stage the star starts to run out of hydrogen at the core and is forced to burn helium to prevent the star from collapsing under its own gravity. When the star is forced to burn helium the star must increase its temperature to maintain the equalibrium between gravity and gas pressure that is pushing out. As the star gets hotter the hydroden in the shell of the star will start to form rapid nuclear reactions and the shell of the star will swell creating a red giant. Depending on the size of the star it will either form a neutron star or a supernova or will become a white dwarf. The nearest star to us is our sun and it is over one million times the size of earth. Some stars have planets orbiting them so they create their own solar system. Sirius or the north star is the brightest star in the sky. The temperature of stars can range from 3600 K to 50000 K and the colour can range from blue to red. There are many kinds of stars The types of stars are blue and red dwarfs, blue and red giants and yellow stars. Red dwarfs are the most common stars and our sun is a yellow star. Blue stars are the hotest types of stars and burn out quickly. When a stars resources start to run out the star swells and increases in size creating a red giant. Red giants are not very hot compared to other stars but getting anywhere near them would still fry your brain. When stars form a red giant the red giant could explode forming a supernova and that supernova could form a nebula. Nebulas are places where stars are born and exploding stars form nebulas. Stars are very cool and people still don't know every thing about them so you will have to discover them on your own astronomy journey.

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