What is the most common type of star in the universe?

The most common type of star in the universe is red dwarf stars. These stars are small, with masses less than half that of our sun, and they burn their fuel very slowly, resulting in long lifespans that can extend to tens of billions, even trillions of years.

Because red dwarfs are so abundant and stable, they make up the majority of stars in our galaxy and likely in the universe as a whole. Unlike more massive stars, which have shorter life cycles, red dwarfs can endure for incredibly long periods without exhausting their hydrogen fuel quickly. This longevity and their prevalence give them the status of the most common type of star, significantly outnumbering yellow dwarfs, blue giants, and white dwarfs.

Yellow dwarf stars, like our sun, are more massive and luminous but less common compared to red dwarfs. Blue giant stars are even rarer, as they are massive stars that burn through their hydrogen rapidly and exist for a much shorter duration. White dwarfs are remnants of stars that have exhausted their nuclear fuel and, while they are numerous due to stellar evolution, they don't form new stars like red dwarfs do.

This understanding of stellar classification and distribution highlights the dominance of red dwarf stars in the cosmos