Subgiant lifespan Calculations

[AlphaLibrae]

Homework Statement

Can you estimate how the time spend on the subgiant branch varies with mass? Quantify this by writing table displaying the lifespan of subgiants in years for a given initial solar mass (1 solar mass, 3, 5, 10, 25, 60).

Homework Equations

I was not provided a relevant equation because I am expected to find one online to help me calculate subgiant lifespans. I did come across the equation

T = 1 / M^2.5

Where T is time in solar lifetime (10^10 years) and M is mass in solar masses.

However, this equation calculates the time spend on the main sequence.

The Attempt at a Solution

I used the equation mentioned in the Relevant Equations to calculate the lives of main sequence stars, as that was another homework tied to the subgiant question. However, this does not help me calculate subgiant lifespans for the given masses. I found online that "the time spent as a subgiant is much less than the time spent on the main sequence or as a giant star", but again, as much as this statement allows me to conceptually understand the answer, I cannot mathematically quantify this. Any assistance would be greatly appreciated.

 

[NateD]

1 Solar Mass: Unknown 3 Solar Masses: Unknown5 Solar Masses: Unknown10 Solar Masses: Unknown25 Solar Masses: Unknown60 Solar Masses: Unknown