The red giant Betelgeuse — don’t say it three times in a row unless you want Michael Keaton to show up and make your dinner guests dance to the Banana Boat Song — is one of the most familiar stars in the sky for people who live in the northern hemisphere. It’s the right shoulder, and one of the brighter stars, in the constellation Orion, the hunter, which is visible even in the night sky of Columbus, with all of its light pollution.
But lately, Betelgeuse is acting strangely. It’s become noticeably dimmer, and fallen out of the ranks of the top ten brightest stars in the northern sky. That might mean nothing, because Betelgeuse is a variable star that shifts in brightness, or it might mean something extraordinary: some scientists think we might be witnessing the death throes of Betelgeuse, and in short order we might see a supernova where Betelgeuse once was. Supernovas occur when the lifecycle of a star of a particular size ends, and the star’s mass is ejected in a titanic explosion. If Betelgeuse were to go supernova it would be brighter in the night sky than the Moon and might even be visible during the day.
Supernovas don’t happen every day, every decade, or every century. One famous example occurred in 1054 A.D., when Chinese, Japanese, Arab, and Korean astronomers all reported observing a new star in the heavens, in the constellation of Taurus the bull, that was so bright it could be seen during the day for weeks and did not fade from view at night until two years later. Modern astronomers believe that the ancient astronomers were seeing a supernova that now appears as the Crab Nebula. Being able to observe a supernova in real time, with the sophisticated technology that is now available, would undoubtedly allow humanity to add significantly to its understanding of the death throes of a star.
And here’s a mind-blowing point. As I write this, Betelgeuse may already have exploded. In fact, it might have already exploded when Columbus sailed for the New World in 1492, or the American Revoluation began in 1776, or World War II ended in 1945. We don’t know for sure, because the light from Betelgeuse takes about 600 years to reach Earth. Whenever you look up at the stars in the night sky, you’re always looking into the past.