The star Betelgeuse in Orion, one of the best-known stellar objects in the sky, has shrunk by 15% over the past decade and a half. Bear in mind the size of Betelgeuse: if our own Sun was placed at the center of this star, its outer surface would extend just past the orbit of Jupiter. Or at least it used to not very long ago.

Some astronomers are wondering if Betelgeuse is shrinking because it’s used up hydrogen as its main fuel and is now “burning” from helium and other heavier elements. Which would mean that it’s in the final stages of a star of its class. When it starts trying to fuse elements like iron and such, some positively hideous astrophysics come into play and Betelgeuse’s internal energy is going to overwhelm its immense gravity…

…and we’ll get to see a rilly big bang called a supernova.

The ...