May 19, 2024
Betelguese's bizarre dimming has astronomers scratching their heads
One of the night sky's brightest stars is now the faintest it's been in a century. Astronomers aren't sure what it means.
One of the night sky’s brightest stars is now the faintest it’s been in a century. Astronomers aren’t sure what it means.

Over the last few weeks, Betelgeuse, the bright reddish star in the constellation Orion, has dimmed to the faintest it’s been in a century. Astronomers have been buzzing with excitement about the event, discussing the star over social media and speculating what might be going on. 

The big question on everyone’s mind is whether the star is about to go supernova and explode. That’s probably not what’s about to happen, astronomers say, but they’re still excited to be witnessing behavior they’ve never seen from Betelgeuse before. There’s a lot astronomers still don’t know about the variable behavior of supergiant stars like Betelgeuse, so any strange activity is a chance to learn more about the lives of stars. 

A Fading Supergiant

For over a century, astronomers have watched Betelgeuse brighten and dim again and again. Betelgeuse is a red supergiant, a star late in its life that has expanded to an enormous size. Bubbles of material rise from inside the star to its surface and sink back down, changing the mix of hotter and cooler stuff on the star’s surface. These changes make Betelgeuse appear brighter and fainter over time.

For about 25 years, Richard Wasatonic, an astronomer at Villanova University in Pennsylvania, has measured the brightness of Betelgeuse with a 10-inch diameter telescope in his backyard. He’s worked with another Villanova astronomer named Edward Guinan, as well as an amateur astronomer named Thomas Calderwood. In October, they noticed that Betelgeuse was getting fainter again. By early December, they realized that Betelgeuse had gotten fainter than it had in the past 25 years and put out a post on a site known as The Astronomer’s Telegram to alert other astronomers.

“It kept getting fainter,” Guinan said. “Every night, it was fainter than the previous night, and I said, ‘Well, it has to stop soon.’ And it hasn’t.” 


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