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The fusion process in a young star (made mainly of Hydrogen) is.
In the fusion process, when the 4 H nuclei are converted into a He nucleus a small amount of mass is lost
as energy.
Eg/ Mass of 4 H nuclei = 6.693 x 10-27kg
Mass of 1 He nuclei = 6.645 x 10-27kg.
What is the difference in their masses?
The mass is released as energy. The energy is given by E = mc 2.
For each fusion reaction the energy released is...
This seems like a small amount of energy but now work out the energy released by 1kg of hydrogen
atoms undergoing fusion.
(Hint: use percentages)
This is ~ burning 2 x 107kg of coal.
If the luminosity (power output) of the sun is 3.9 x 1026W, work out how much Hydrogen the sun 'burns'
each second, and how much the equivalent in coal would be.
If the mass of the Sun is 2 x 1030kg, how many years can the sun burn for?
But after the Sun will continue to burn He, Be, etc in more complex reactions. Other stars burn at different
rates and have different masses resulting in some having much shorter lifetimes (5000yrs) and some
much longer.
What factors affect the lifetime of a star?