Betelgeuse is getting weird again. what gives? : ScienceAlert

Since what has come to be known as the Great Dimming that occurred in the latter half of 2019 and early 2020, the red giant star Betelgeuse hasn’t stopped making fun of it.

The regular cycles of brightness fluctuations of the dying star have changed, and Betelgeuse is now uncharacteristically bright. At the time of writing, she is sitting 142 percent of its natural brightness.

It has been swinging back and forth on a small but steady upward trend for several months and hitting a The most recent peak is 156 percent in April.

Currently, Betelgeuse is the seventh-brightest star in the sky—up from its normal position as the tenth-brightest, prompting speculation that Betelgeuse is about to explode in a spectacular supernova.

Unfortunately, it probably isn’t. Although Betelgeuse is about dead on cosmic time scales, on human time scales the supernova could be 100,000 years away.

According to scientists, its current behavior is likely to be a bit of constant fluctuation after the 2019 darkening, and the star will return to normal within a decade.

Located about 700 light-years from Earth, Betelgeuse is one of the most spectacular stars in the sky. It hangs above us, glowing like a bloodshot eye, a star in the red giant phase that marks the end of its life.

But Betelgeuse is an unusual type of star, even for a red giant. Once upon a time, it was an absolute beast: a blue-white O-type star, the most massive stellar weight class.

Stars in this mass range burn through their hydrogen stores more quickly than stars of lighter weight. Betelgeuse just about 8 to 8.5 million years ago. Compare that to a star like the Sun, which is 4.6 billion years old and is in the middle of its hydrogen-burning age.

Betelgeuse has changed its spectral type as it roughly passes through its hydrogen reserves. It now fuses helium into carbon and oxygen and has ballooned to a gigantic size: approx 764 times the size of the Sun and about 16.5 to 19 times its mass.

Eventually, it will run out of fuel to burn, go supernova, shed its outer matter, and its core will collapse into a neutron star.

The Great Dimming Event saw the star’s brightness decrease by a significant amount, approximately 25 percent. Astronomers scrambled to find out why. It turns out that cooling on the surface of Betelgeuse caused a huge cloud of dust to condense on the star.

This cloud was later ejected, partially obscuring Betelgeuse, making it appear faint. Scientists say it’s fairly normal behavior for a red giant star; We don’t usually get a front row seat like that.

Before the Great Dimming, Betelgeuse also had fluctuations in brightness on regular cycles. The longest of these cycles is about 5.9 years; last 400 days. But the Great Dimming seems to have caused some changes in these fluctuations.

A new paper, led by astrophysicist Morgan MacLeod of the Harvard-Smithsonian Center for Astrophysics, uploaded to the arXiv preprint server, finds that The 400 day cycle seems to have been halved.

This pulsating cycle is driven by the expansion and contraction within the star. According to simulations by MacLeod and colleagues, the convective plume inside Betelgeuse could have burned away, becoming the material that separates from the star.

In the process, this outflow disrupted a phase of the 400-day cycle, producing the roughly 200-day cycle that the star is currently exhibiting.

Therefore, Betelgeuse is still reeling from the great dimming, which means that it is unlikely that its current brightening is also associated with ongoing problems.

As astrophysicist and Betelgeuse expert Andrea Dupree of the Harvard-Smithsonian Center for Astrophysics — co-author on the Maclean team — Tell Scientific American“Just imagine if you ejected a large chunk of the material. Then everything else would flow out, and it would roll… I think what happens is the upper layers have trouble getting back to normal.”

However, the team predicts that eventually, normal life will return to Betelgeuse, and it will continue to live thousands of years in relative peace for some time to come.