Stars initially form from clouds of dust and gas. The force of gravity makes the gas and dust spiral together to form a protostar.
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Gravitational energy is converted into heat energy so the temperature rises. When the temperature gets high enough, hydrogen nuclei undergo nuclear fusion to form helium nuclei and give out massive amounts of energy in the form of heat and light.
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A star is born. Smaller masses of gas and dust may also pull together to make planets that orbit the star.
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The star immediately enters a long stable period, where the heat created by the nuclear fusion provides an outward pressure to balance the force of gravity pulling everything inwards. It consumes massive amounts of hydrogen.Lasts for billions of year
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Eventually the hydrogen begins to run out. Heavier elements such as iron forms which are made in the nuclear fission of helium. The star then swells into a red giant, if it’s a small star, or a red super giant if its a big star. surface cools= red
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A small-to-medium-sized star like the sun then becomes unstable and ejects it’s outer layer or dust and gas as a planetary nebula.
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This leaves behind hot, dense solid core-a white dwarf, which cools down to form a black dwarf and eventually disappears.
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Big stars=Eventually they explode in a supernova, forming elements heavier than iron and ejecting them into the universe to form new planets and stars.
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8. The exploding supernova throws the outer layers of dust and gas into space, leaving a very dense core called a neutron star. If the star is big enough this will become a black hole.
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Gravitational energy is converted into heat energy so the temperature rises. When the temperature gets high enough, hydrogen nuclei undergo nuclear fusion to form helium nuclei and give out massive amounts of energy in the form of heat and light.
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