How is the age of the sun determined?

The sun is a main sequence star, and its typical lifetime is between 10 and 11 billion years. Main sequence stars burn fuel slowly, whereas giant stars burn fuel rapidly, and their current life span is determined by the amount of fuel they have burned thus far (from hydrogen to helium). Therefore, the current age of our solar system, which includes the sun and other planets, is approximately 4.5 billion years. At 10 billion years, the sun would have burned through all of its hydrogen to helium, turning into a redgiant that will burn helium for an additional 100 million years before collapsing on its core and transforming into a white dwarf.

The age of the Sun is determined using various methods, including radioactive dating of meteorites, observations of other stars at various stages of their evolution, and models of stellar evolution. By studying the composition of meteorites and using radioactive dating techniques, scientists can estimate the age of the oldest materials in the solar system, providing a lower limit for the Sun's age. Observations of other stars allow astronomers to develop models of stellar evolution, which can then be applied to the Sun to estimate its age based on its current characteristics and stage of evolution. These methods collectively suggest that the Sun formed around 4.6 billion years ago.