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This Fading Star Wasn’t on the Brink of Death After All—It Was Just Dusty

After four months of unexpected dimming, the red supergiant star has perked back up, and astronomers may have a new explanation for the fluke

The red supergiant star Betelgeuse, as seen by the Atacama Large Millimeter/submillimeter Array (ALMA) (ALMA (ESO/NAOJ/NRAO)/E. O’Gorman/P. Kervella)
smithsonianmag.com

After setting the astronomy community ablaze with discussions of its demise, the star Betelgeuse has thrown stargazers for another loop. After four months of rapid fading, interpreted by some as a sign of impending explosion, the red supergiant has perked back up—and its stint of low light may have simply been the product of some serious stellar dust, obscuring Betelgeuse’s glow, new research suggests.

“Some people wanted this to be seen as the death throes of the star, and it’s very much not,” Emily Levesque, an astrophysicist at University of Washington and an author on a study that will soon publish in Astrophysical Journal Letters, tells Lisa Grossman at Science News.

Known for marking the right “shoulder” of the constellation Orion, Betelgeuse has long been one of the brightest and most recognizable stars in the sky. Like other so-called variable stars, Betelgeuse goes through regular cycles of brightening and dimming. But last October, it began to lose its luster at an unprecedented pace, piquing the interest of astronomers worldwide, some of whom began to wonder if the star might be on its last legs. If that was the case, it would likely explode in a supernova—a violent stellar cataclysm that could outshine the moon and make the star visible even in daylight.

Then, at the end of February—after four months of unprecedented dimming—the star got a second wind. “We had the minimum on February 20, plus or minus some days,” Ed Guinan, an astronomer at Villanova University, tells National Geographic’s Nadia Drake. The star, it seemed, had been resuscitated back to life.

Levesque and Massey theorized that at least two alternative explanations for Betelgeuse’s unexpected downturn were likely. In one, the star might have experienced a temperature drop, cooling down into a dimmer state; in another, it could have coughed up a fit of dust that temporarily obscured its starlight, making it appear fainter than it actually was. After observing the star on February 14, the researchers found the star ran just as hot as usual, leaving—by process of elimination—the possibility of stellar schmutz, produced by Betelgeuse itself.

Speaking with Science News, Guinan describes the dust model as “viable,” but points out other factors could be at play. “It … doesn’t rule out changes in the star itself,” he says. “I think the jury is still out.”

Cosmic dandruff may not be as exciting as a star hurtling toward its death. But the end of this story doesn’t have to be an anticlimactic one: Like any other star of its kind, Betelgeuse will eventually go boom. The possibility remains that it already has: At some 650 light-years from Earth, the star’s light takes 650 years to reach us.

The upper limit many astronomers have placed on its death is about 100,000 years from now. So while Betelgeuse is certainly worth a glimpse, you might want to spend that time occasionally turning your telescope elsewhere.

About Katherine J. Wu
Katherine J. Wu

Katherine J. Wu is a Boston-based science journalist and Story Collider senior producer whose work has appeared in National Geographic, Undark magazine, Popular Science and more. She holds a Ph.D. in Microbiology and Immunobiology from Harvard University, and was Smithsonian magazine's 2018 AAAS Mass Media Fellow.

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