# What is the length of time for each fusion process in a massive star?

In a massive star (i.e. an O5 star), first hydrogen is fused into helium, then helium is fused into carbon. This process continues to neon, oxygen, and finally silicon burning. So I am wondering, how long does it take for each process to commence?

• Here's a timetable for a 25 $M_\odot$ star. en.wikipedia.org/wiki/Type_II_supernova#Formation Commented Dec 16, 2020 at 8:45
• @PM2Ring You can use this in an answer :D Commented Dec 16, 2020 at 14:08

My stellar astrophysics text, Francis LeBlanc's An Introduction to Stellar Astrophysics, gives the following quantities for the stages of burning in a $$25M_{\odot}$$ star (citing models by Arnould & Samyn 2001). This is somewhat less massive than a typical main sequence O5-type star, and with higher masses come higher core temperatures and shorter evolutionary timescales. Nonetheless, it should give you a reasonable order-of-magnitude idea of how long it takes for these processes to play out in a massive star.
Hydrogen $$6.0\times10^7$$ $$7\times10^6$$ years
Helium $$2.0\times10^8$$ $$5\times10^5$$ years
Carbon $$9.0\times10^8$$ $$600$$ years
Neon $$1.7\times10^9$$ $$0.5$$ years
Oxygen $$2.4\times10^9$$ 6 days
Silicon $$4.0\times10^9$$ 1 days