A star converts all its hydrogen to helium achieving 100% helium composition. It then converts helium to carbon via the reaction 
+ 7.27 MeV. The mass of the star is 5.0 × 10 32 kg and it generates energy at the rate of 5× 10 30 watt. How long will it take to convert all its helium to carbon ?
Text Solution
Verified by ExpertsCHECK THE SOLUTION.
Sol. 4 × 10 –3 kg of helium contain 6.023 × 10 23 helium atoms
Therefore number of helium atoms in the star
= 
× 5.0 × 10 32 = 7.5285 × 10
58 atoms
3 helium atoms produce 7.27 MeV
= 7.27 × 1.6 × 10 –13 joule energy
Total energy produced by all the atoms
= 
× 7.5287×10 58 = 29.2 × 10
45 joule
Power = 5 × 10 30 watt (given)
time taken to convert all helium atom
into carbon = 
= 5.84 × 10 5 sec
= 1.85 × 10 8 years
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