The key to a star’s appearance and lifespan is its mass. Heavier stars shine brighter but live shorter lives than less-massive ones. An example can be seen in the two bright stars of Alpha Centauri, the leading light of the constellation Centaurus. It’s the closest star system to our own, at a distance of four light-years. One of the stars is about 10 percent more massive than the Sun, while the other is about 10 percent less massive than the Sun. With so little difference, you might expect them to be almost identical, but they’re not. The heavier star, Alpha Centauri A, burns through the nuclear fuel in its core faster than its companion, Alpha Centauri B. As a result, it shines three times brighter. The surface of Alpha Centauri A is also hundreds of degrees hotter, so it looks yellow-white versus the yellow-orange of Alpha Centauri B. While “A” is far brighter, “B” has a much longer future to look forward to. Its “normal” lifetime should last about half again as long as that of its
