Remember that as the mass goes up, so does the central temperature as required to maintain hydrostatic equilibrium. This leads to two major differences between solar mass and more massive stars.
|9 x 109 years
500 x 106 years
15 x 106 years
3 x 106 years
Why is this? Because Luminosity increases much faster than Mass.
So, no helium flash, no horizontal branch phase.
This last point is very important and leads into two fascinating topics - Supernovae II and Galactic Chemical Evolution.
|10 x 106||H -> He|
|100 x 106||4He2 -> 12C6|
|600 x 106||12C6 -> 16O8 (24M12)|
|1500 x 106||16O8 -> 20Ne10 (32S16)|
This is the way Nature likes to work - these reactions release energy.
For EQUILIBRIUM fusion reactions, Iron is the end of the line
Therefore light elements fuse to push elements up the curve. Similarly for the heavy elements, fission reactions tend to push elements up the curve from the right and release energy. Fusing He to make Be goes the wrong way and this reaction requires energy INPUT to make it happen. Nature doesn't care for these sorts of reactions.
|H fusion||4 x 107K||7 x 106 yr|
|He fusion||20 x 107||5 x 105 yr|
|Carbon fusion||60 x 107K||600 yr|
|Neon fusion||120 x 107||1 yr|
|Oxygen fusion||150 x 107K||6 mo|
|Silicon fusion||270 x 107K||1 day|