Supergiant stars are massive, luminous stars that have evolved beyond the main sequence phase. They are extremely hot and have short lifespans compared to other types of stars. The exact lifespan of a supergiant star depends on its initial mass and metallicity, but in general, they have lifespans of a few million to a few hundred million years.

The most massive supergiant stars, those with initial masses greater than about 100 solar masses, have the shortest lifespans. They evolve rapidly and can explode as supernovae within a few million years. Less massive supergiant stars, with initial masses of around 10 solar masses, can have lifespans of up to a few hundred million years.

The metallicity of a supergiant star also plays a role in its lifespan. Metallicity refers to the abundance of elements heavier than helium in the star. Supergiant stars with higher metallicities tend to have shorter lifespans than those with lower metallicities. This is because metals act as catalysts for nuclear fusion reactions in stars, which causes them to burn through their fuel more quickly.

Supergiant stars are important because they play a significant role in the evolution of the universe. They produce heavy elements through nucleosynthesis and enrich the interstellar medium with these elements when they explode as supernovae. Supergiant stars also help to regulate the star formation process by creating bubbles of hot gas that can prevent the formation of new stars.