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SUN

nearly all the mass in our solar system is in the sun very large the source of most of the energy we receive. Nuclear Fusion is the energy source- hydrogen nuclei fuse to make helium nuclei- produces huge amounts of energy hydrogen nucleus + hydrogen nucleus = helium nuclei In stars larger than ours, helium nuclei can be fused together to create heavier atomic nuclei As Earth contains many of these; carbon, oxygen, nitrogen etc, it is believed the Solar System was formed from a previous exploded star

How Planets and Stars Formed

As the gas falls together it gets hot Star forms when it becomes hot enough for nuclear fusion reaction to start This releases energy and keeps star hot Outward pressure from expanding gases is balanced by the force of the sun's gravity Gravity pulls in surrounding dust and gas and planets from Measuring Distance in Space light years- the distance light travels in 1 year

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