How do you calculate main sequence life span for a solar mass star?

Question

so how would you answer a question if it asked you to calculate the expected main life sequence life span for lets say a 13 solar mass star?

Answer 1

The lightest stars, of less than a tenth of a solar mass, may last over a trillion years. For the heaviest stars, however, this mass-luminosity relationship poorly matches the estimated lifetime, which last at least a few million years.

Since the luminosity gives the amount of energy radiated per unit time, the total life span can be estimated, to first approximation, as the total energy produced divided by the star's luminosity.

Answer 2

Mass is the main factor in determining how long a star stays on the main sequence.  

The lower mass limit for a main sequence star is about 0.08 that of our sun.  Less than this and the star fails to get hot enough to start fusing hydrogen, and thus becomes a "failed star" known as a brown dwarf.  

The upper limit is thought to be between 150 and 200 solar masses.  

The greater a star's mass, the greater its temperature, which means the greater its luminosity (how bright it is).  

Our sun will spend about 10 billion years on the main sequence (it's currently about halfway through its time on the main sequence).  

Larger (more massive) stars burn through their fuel more quickly and thus spend less time on the main sequence.  Less massive stars spend more time on the main sequence.  

For a formula and how to calculate, see the link below: