Webxiang and rix 2 determined the ages of stars in the subgiant phase of evolution — which occurs when a star runs out of core hydrogen — as a means of understanding how the milky way formed. Webstellar evolution is the process by which a star experiences a sequence of drastic variations during its stellar life. Depending on the initial stellar mass, this lifetime ranges from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the age of the universe at 13. 7 billion. Webwhen the stars used up their nuclear fuel, they started to evolve. The evolutionary processes of stars depend upon their initial mass. More massive stars explode as supernovae,. Webwhat stages of life do stars go through? Watch the birth of stars in “stellar nurseries” and their transformation into red giants and supergiants. Find out what causes supernovae, how black holes form, and what happens to stars after they die.