Question

What is the average lifespan of a star?

Answer 1

The lifespan of a star depends on its mass. It could vary from a few million years to few trillion years. A star resembling our sun in its mass would last for about 10 Billion Years.

Explanation:

The life time of a star depends on its mass and to some extent its opacity. Massive stars burn their nuclear fuel fast and die soon whereas less massive ones burn it slow and live longer. The lifetimes span six orders of magnitude (`10^6` Years - `10^{12}` Years)

Maximum possible Stellar Lifetime
The lower limit for the mass of a star, called the Brown Dwarf Limit is `0.08M_{sun}`. A star with this mass live for about 2-5 Trillion years .

Minimum possible Stellar Lifetime
The upper limit for the mass of a star, called the Eddington Limit is about ( roughly ) `100M_{sun}`. A star of this mass live for about `100, 000 Years`.

Lifetime of our Sun
A star like our sun can live for about `10` Billion Years.