Two bright reddish-orange stars pass high across the south early this evening: Betelgeuse, at the shoulder of Orion, the hunter; and, well to its upper right, Aldebaran, the eye of Taurus, the bull. An even redder star perches below Orion’s feet, although you need binoculars or a telescope to see it. Hind’s Crimson Star is one of the most remarkable stars in the galaxy. It pulses in and out like a beating heart, with each beat changing the star’s size by tens of millions of miles. The star is quite near the end of its life. It no longer produces nuclear reactions in its core, although it does produce them in a thin shell around the core. At a minimum, Hind’s Crimson Star is hundreds of times wider than the Sun. But the star is unstable. The energy from the shell around the core heats the star’s outer layers, causing them to puff up. As these layers expand, they cool, then fall inward again. Each cycle takes about 14 months. The surface of the star is so cool that it shines reddish oran
