Question

1. The Lifetime of the Sun. The total mass of the sun is about 2 x 10³⁰ 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) Use the given data to calculate the total mass of hydrogen available for fusion over the lifetime of the sun.

       b) The sun fuses about 600 billion kilograms of hydrogen each second. Based on your results from part (a), calculate how long the sun’s initial supply of hydrogen can last (in seconds, and in years); that is, calculate the expected lifetime of the sun.

       c) Given that our solar system is now about 4.6 billion years old, when will we need to worry about the sun running out of hydrogen?

Answer 1

SSummary:

a)Amount of hydrogen available in core for fusion in time of formation of sun = 0.195*10³⁰

b)The total expected lifetime of sun = 3.25*10¹⁷ seconds

OR 1.0*10¹⁰ Years or 10 billion years

c) The time remaining for sun = 5.4 billion years

So we need to worry only after that.