How long will it be before we need to start worrying about the Sun running out of hydrogen for fusion?
Lifetime of the Sun - The total mass of the Sun is about 2 x 1033 kg, of which about 75% was hydrogen when the Sun formed. However, only about 13% of this hydrogen ever becomes available for fusion in the core. The rest remains in layers of the Sun where the temperature is too low for fusion. (a) Based on the given information, calculate the total mass of hydrogen available for fusion over the lifetime of the Sun. (b) Combine your results from part (a) and the fact that the Sun fuses about 600 billion kg of hydrogen each second to calculate how long the Sun's initial supply of hydrogen can last. Express your answer in both seconds and years. (c) Given that our solar system is now about 4.6 billion years old, how long will it be before we need to start worrying about the Sun running out of hydrogen for fusion?