17, and is thought to have written the Latin work De Astronomia, described the star in the right shoulder of Orion has having a similar color to Saturn - which is yellow. The ancient Roman astronomer Gaius Julius Hyginus, who lived from about 64 B.C. Most stars observed over human history had the same color recorded in the past as they display today, the team found. The team analyzed ancient descriptions of more than 200 stars whose colors should have been visible to the naked eye in the past few thousand years.
Two millennia ago, the star was a completely different color, astrophysicist Ralph Neuhäuser and colleagues report in a paper in press in Monthly Notices of the Royal Astronomical Society. The Great Dimming isn’t the first time humans have recorded a major change in Betelgeuse’s personality. “That would be proof” that the brightness changes were due to a single outburst, Guinan says. “Those little variations you’re seeing…could easily be present right before the Great Dimming,” Guinan says.ĭupree’s team predicts that the dust Betelgeuse lost could become visible to some telescopes on Earth in 2023. Those extra observations might reveal recurring changes that have always been there, rather than picking up on something truly new.
“You can follow the star all year round.” Dupree’s paper is the first to include those daytime data. Usually that leaves a hole in the datasets of astronomers who track its periodic behavior.īut amateur observer Otmar Nickel of Mainz, Germany, developed a technique to measure Betelgeuse’s brightness using multiple images taken during the day. From May through August every year, Betelgeuse is too close to the sun from Earth’s perspective to be seen at night. One confounding factor is a new set of observations of Betelgeuse during the four-month period when it’s usually out of view. Studying Betelgeuse’s growing pains and death throes can tell us about our own origins.īut while this picture of Betelgeuse holds together, it is still speculative, Guinan cautions. That’s important to know because many of the elements that make up planets and people were formed in stars undergoing what Betelgeuse is going through right now. If this picture is correct, it means red supergiants like Betelgeuse can spray material into interstellar space in discrete bursts, rather than a continuous stream. The star’s surface plasma is sloshing around as it returns to equilibrium. She calculates that Betelgeuse ejected several times the mass of the moon from its surface, leaving a large cool spot behind. The wonkiness is a sign of the star struggling to recover from the loss of material in 2019, Dupree says. Instead of a regular thrum, the oscillations are “like an unbalanced washing machine, going ‘wonka wonka wonka,’” Dupree says. That regular drumbeat has since grown erratic. “For 200 years, it had a nice, 400-day oscillation in brightness,” says Dupree, of the Harvard & Smithsonian Center for Astrophysics in Cambridge, Mass. As the star breathed in and out - ballooning out before shrinking back down - its brightness went up and down. In its non–Great Dimming life, Betelgeuse’s brightness was on a quasi-periodic dimmer switch. The star’s regular pulsating brightness, it seems, went completely out of whack. The surface of the star also cooled down, contributing to the dimming ( SN: 6/16/21).īut what happened next was equally surprising, astrophysicist Andrea Dupree and colleagues report in a paper submitted August 2 to.
That material cooled, condensed into dust and blocked the star’s face from the perspective of Earth months later ( SN: 11/29/20). Months of subsequent observations led researchers to an explanation: The star had coughed out a big bubble of plasma. In late 2019, Betelgeuse captured astronomers’ attention when it suddenly grew dark for several months - an event astronomers now call the Great Dimming. “You think you have it, and all of a sudden, it changes.” The “Great Dimming” “This star always fools you,” says astronomer Edward Guinan of Villanova University in Pennsylvania, who has studied Betelgeuse for decades and was not involved in the new works. Together, these studies could tell researchers about how stars spew their guts into space and hint at how long it will be before Betelgeuse explodes in a supernova.
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