What is the max theoretical lifespan of a star?
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14 Answers
Answered 4 years ago · Author has 1.9K answers and 8.7M answer views
The lifespan of a star varies tremendously depending on the mass of the star, and it may be counter-intuitive. Main-sequence stars are mostly hydrogen and you might think the more fuel they have, the longer they will last, but the opposite is true.
The larger the star, the more pressure and heat they have at their core, more heat & pressure increases the rate of fusion, so the the most massive stars burn through their fuel much more rapidly.
The most massive stars in the universe have a lifespan of a few million years. When they have fused all the light elements around their cores to Iron 56, they explode as supernovae leaving behind a remnant black hole.
The smaller stars, red dwarfs, due to their lower core heat and pressure have a relatively small amount of fusion occurring, so they can take 100’s of billions of years to burn through their fuel.
Medium size stars like our Sun, have lifespans of around 10 billion years, the end coming after they expand into red giants and then contract and fade into white dwarfs.
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, Astrophysics graduate student
Answered 3 years ago · Author has 137 answers and 745.6K answer views
It is approximately 11 trillion years.
The more massive a star, the shorter its lifespan. We have good observational evidence of the lifespans of massive stars, which burn out in only a few million years. However, the Sun’s lifespan is 10 billion years—only slightly shorter than the age of the universe. This means that we have no observational evidence for the lifespans of stars much smaller than the Sun, because none of them have died in the history of the universe.
For massive stars, we find that lifespan decreases roughly as the 2.5th power of mass. Since the Sun is expected to live 10 billion years, we get:
tlife=(10billionyears)(M/Msun)−2.5
We can extrapolate this to 0.08 solar masses—the smallest stars possible, because objects smaller than this don’t have enough central pressure or temperature to fuse hydrogen. We get a lifespan of 6 trillion years using this equation.
A more accurate calculation, done with stellar models instead of wild extrapolation, gives 11 trillion years for the lifespan of the smallest stars. This is 80 times longer than the current age of the universe. It will be a long, long time before we have evidence to confirm this number.
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