A year ago, the bright red star Betelgeuse in the Orion constellation made headlines when astronomers noticed a strongly fading episode that astronomers could not explain. They still can not, although they keep trying.
The tension is now particularly high, as the star, which usually fades and brightens on a regular schedule, will soon have to start fading again, for the first time since last year’s strange antics. Scientists hope that this year’s observation of Betelgeuse will put last year’s episode in context, which may shape astronomers’ understanding of star activity more generally. One such astronomer shared an update at the 237th meeting of the American Astronomical Society, held virtually in January, ahead of the fading predicted in April.
“We want to see if last year was really unique,” Andrea Dupree, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, told Space.com after the conference.
“What if it happens again? Then I do not know,” she said. ‘I do not know if it’s going to be a one-off life [event] whether it is going to happen again and whether it is now in a new phase and what it means. ‘
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What she and her colleagues do know is that scientists have been recording detailed observations of Betelgeuse for 150 years, and that nowhere in these records does anything like the blurring of last year occur. Usually the star fades and brightens during a cycle of about 420 days in a breathable rhythm, which grows and becomes smaller.
But in December 2019, skywatchers noticed that something strange was happening when Betelgeuse began to fade.
“It’s never been as faint as last February,” Dupree said. Even just star gazing, and Betelgeuse spotted in early January at the 235th American Astronomical Society meeting from Honolulu, 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. This is not how it is supposed to be. ‘
Some observers hoped that this was a sign that people were on the verge of getting a seat for Betelgeuse’s dramatic downfall. As an old, red supergiant, according to NASA, Betelgeuse is doomed to a confusing fate: when the star’s fuel runs out, it will explode in a brilliant supernova and spit out its inner walls over the cosmic environment. (In fact, the star may have already done so, and scientists are just waiting to see the aftermath.)
Dupree did not think this was the most likely scenario for last year’s antics. But if scientists do catch Betelgeuse at the perfect time, just before it explodes, the observations will be unprecedented.
‘Nobody knows what a star does right before it goes supernova, “Dupree said.” People may have watched six months before or two years before, but until we have a clear overview of the entire sky and the sky, we have no information about what happens the night before it blows up. . “
Although no supernova will soon be realized, more observations of the bright Betelgeuse are still useful, especially if the star is doing something unusual. “The sun is actually the only star we can see in detail and can see what is happening, and Betelgeuse is the next best candidate,” Dupree said.
She especially hopes that Betelgeuse astronomers can learn about stellar eruptions. With the Hubble Space Telescope observations collected in the fall of 2019, before Betelgeuse began to fade, scientists concluded that the star spewed out a large amount of dense gas, Dupree said. This in itself is not too uncommon, though it is strange that this eruption came from a different region of the star than scientists have previously noted, Dupree said.
She suspects that, as the masses continued to move away from Betelgeuse, it slowly cooled to dust – dust that she said would have caused the apparent fading that was so striking last year. Other astronomers think that ejection was accidental and that a large cool spot on the star’s surface caused the strange fading.
Dupree’s hope is that observing Betelgeuse this year could help scientists distinguish between these two scenarios and address additional questions such as the strange location of the eruption.
“How does the star lose material?” she said. “Does it flow softly? Does it come out in bursts? Does it come from different parts of the star? How does it change when it moves from the surface of the star, which is hot, to the interstellar medium, which is cold?”
It is convenient that eclipse took place about halfway last year during a three-year program in which Dupree had already arranged for the Hubble Space Telescope to report to Betelgeuse four times a year. These are some of the Hubble observations that spotted the mass of matter moving away from the star before its eclipse began.
Hubble recently reported to the star in February; the last of the allotted observations will take place in April, Dupree said, although she plans to ask for extra time with Hubble, given the star’s recent activity.
But Betelgeuse is a troublesome target; from late April to late August, it’s too close to the sun in our sky for Hubble and instruments on the ground to see it, Dupree said. This is especially uncomfortable, as the star’s normal cycle of about 240 days puts it at its most beautiful, just as humans cannot see it.
Between Hubble observations last summer, Dupree deployed NASA’s solar spacecraft STEREO-A, about a third of an orbit located behind the earth. When the sun blocks Betelgeuse from the earth, the spacecraft has a clear view of the star. The spacecraft will make four or five more such observations this summer, following Hubble’s last chance to see the star this spring.
For now, the star is still keeping astronomers on their toes.
“Betelgeuse is ‘quiet,'” Dupree wrote in an email update on March 1, adding that she was beginning to suspect that the star would not fade his predicted April, according to the schedule he had been following for so many years. that outburst changed his personality in 2019! “
Whether Betelgeuse fades or not, Dupree and her colleagues will watch and eager to sharpen the star’s secrets. “We’ll see,” she said, “that’s what’s always nice!”
Email Meghan Bartels at [email protected] or follow her on Twitter @meghanbartels. Follow us on Twitter @Spacedotcom and on Facebook.