cycle

What's going to happen to all the stars in the Universe as they get older? Well, just as nothing can live forever, stars can't live forever also. Why? Because they run on fuel: burning hydrogen into helium, for example. When they run out of fuel, something's gotta give. Barbara Ryden reminds us of an excellent and appropriate quote by Dylan Thomas: Do not go gentle into that good night. Rage, rage against the dying of the light. But what exactly happens to the star depends very sensitively on what the mass of the star is. If you've got a tiny little star, less than about 40% of the mass of…