Lifestyles of the Stars

Astrophysicists can use knowledge of nuclear fusion to chart the life histories of stars on a simple "age-mass diagram." A newborn star appears at the top of each column. As we look downward, each diagram reveals how the star changes with age until, at the bottom, it dies. The column on the left depicts very low mass stars, which start life with less than one-tenth of the Sun's mass. These midgets never achieve ongoing nuclear fusion in their cores, so they change very little as time passes. They spend trillions of years as failed stars known as brown dwarfs. Low-mass stars, which start their lives with somewhat less mass than that of the Sun, do achieve fusion but they ration their energy supply for hundreds of billions of years before losing their outer layers and dying as white dwarfs. The middle column features intermediate-mass stars such as our Sun. These stars, which range up to 10 times the Sun's mass, pace themselves with only slightly less economy than their low-mass brethren. They fuse hydrogen in their cores for billions of years before swelling to become red giants and then laying bare their white dwarf cores. The final two columns display the most profligate star types: high-mass stars, which range from 10 to 20 times the mass of the Sun, and very high mass stars, from 20 to a gargantuan 100 times the Sun's mass. These giants burn their fuel at a furious clip. In less than 100 million years, they undergo catastrophic gravitational collapse. They then explode as supernovas, leaving behind neutron stars or black holes, or they collapse directly into black holes.