Life of the Sun

[Bazile]

The sun has anywhere between 3-5 billion years of radiant energy left in it - ( depending on what literature you are reading )

3 , 4 , 5 , whatever - my question is how are these figures arrived at ?
Sounds like guess work , to me - Yes ?

[eifionlewis]

No i wouldnt say guess work, it is an estimation for sure, as noone can be totally accurate (hense the 3-5 bit), but i think its arrived at by analysing energy given out by the sun and analysing the relative change over a long period of time in composition of the suns gasses (to see whats being burned up).

Pretty accurate figures are available as to the size of the sun, and also there are good ideas as to what the composition profile is... so its just a matter of working out how long it would take for the fuel to run out.... calculations that are beyond my grasp so i wont even try!

[Teddio]

We know the mass of hydrogen fuel in the Sun's core and the rate that hydrogen nuclei are being fused into helium nuclei. We can estimate the length of time it will take to use the hydrogen fuel up to an accuracy of plus or minus a billion years. (Before the Sun swells up to form a Red Giant) It's similar to estimating the lifetime of a candle!