What she and her colleagues do know is that scientists have been recording detailed observations of Betelgeuse for 150 years, and nowhere in those records does there appear anything like last year’s fading event. Usually, the star dims and brightens over a cycle of about 420 days in a breath-like rhythm, growing and shrinking in size and luminosity alike.
But in December 2019, skywatchers noticed something strange was happening as Betelgeuse began to dim.
“It’s never been as faint as it was last February,” Dupree said. Even just stargazing, catching sight of Betelgeuse from Honolulu in early January during the 235th American Astronomical Society meeting, the difference was clear, she said. “The constellation just looked weird, absolutely weird. The bright red star in the shoulder of Orion was not there, it was fainter than the others. That’s not how it’s supposed to be.”
Some observers hoped it was a sign that humans were about to get a front seat to Betelgeuse’s dramatic demise. As an old, red supergiant, according to NASA, Betelgeuse is doomed to a messy fate: when the star runs out of fuel, it will explode in a brilliant supernova, spewing its innards across the cosmic neighborhood. (In fact, the star may have done so already, and scientists are just waiting to see the aftermath.)
Dupree didn’t think that was the most likely scenario for last year’s antics. But if scientists do indeed catch Betelgeuse at the perfect time, just before it explodes, the observations would be unprecedented.
“Nobody knows what a star does right before it goes supernova,” Dupree said. “People have looked maybe six months before or two years before, but until we have a nightly survey of the whole sky and all the sky, we don’t have any information on what happens the night before it blows up.”
Even if no supernova materializes soon, more observations of bright Betelgeuse are still helpful, particularly when the star is doing anything unusual. “The sun is really the only star that we can see in detail and see what happens, and Betelgeuse is the next best candidate,” Dupree said.
