Lifecycle of a Sun

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Life Cycle of the Sun 1) Before nuclear fusion, when the sun was still being created in the interstellar nebula, it was just a protostar. A protostar forms when gravity and pressure begin to condense matter in the centre of the nebula, but no nuclear fusion is yet taking place. When nuclear fusion begins, a star is "born". Our sun started burning hydrogen at 4.5 billion years ago. When the sun started it was a little smaller, less bright and cooler than it is today. 2) The sun is in the middle of its lifespan, and is currently in the main sequence
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phase. At this stage in its life the sun is fusing hydrogen into helium. 3) As the Sun becomes older, it grows slightly larger, brighter and hotter. At about 1.1 billion years from now the Sun will be 10% bigger than it is now. As a result, the extra solar energy will dry up Earth's atmosphere and many kinds of life. In about 3.5 billion years, the sun will be 40% bigger and will probably mean that all life on Earth will cease to exist. The next stage will be for the sun to become a Red Giant. 4) Then ...

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