Which type of star has the longest lifespan?

Low mass stars have the longest lifespan among the various types of stars, primarily because of their slower rate of nuclear fusion processes. These stars, such as red dwarfs, burn their hydrogen fuel at a significantly lower rate compared to high mass stars. Consequently, while high mass stars may shine brightly for a short period, they exhaust their nuclear fuel much more rapidly and go through life cycles that last only a few million years. In contrast, low mass stars can remain stable and continue to fuse hydrogen for trillions of years, far exceeding the lifespan of their high and medium mass counterparts.

Additionally, the long lifespan of low mass stars allows them to evolve through different stages of stellar development over an extended timeframe, ultimately leading to their transformation into red giants and then to white dwarfs over billions of years. This extended life cycle is a direct result of their lower mass and the resulting gravitational pressures that influence their internal fusion processes, resulting in a significantly longer period of stellar activity.