Betelgeuse’s early dimming was recently caused by an enormous cloud of material that blew the supergiant star into space, a new study suggests.
The bright star Betelgeuse, which forms the shoulder of the constellation Orion (The Hunter), is about 11 times more massive than the Sun, but 900 times voluminous. That inflated state shows that Betelgeuse is close to death, which will come in the form of a violent supernova explosion.
In the fall of 2019, Betelgeuse began to dim significantly, loses about two-thirds of its brightness until February. This dramatic dip led to speculation that the death of the star could be dire – perhaps just weeks away. (From our perspective, however; Betelgeuse lies about 500 light-years from Earth, so everything we see with the star today happened centuries ago.)
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But the dramatic sky show did not happen: Betelgeuse turned through the dimming episode and returned to its normal brightness by May of this year. The recovery created a new round of speculation, this time about the cause of the dimming. Some scientists attributed the doldrums to a light-blocking dust cloudfor example, while others said large starspots on the surface of Betelgeuse were probably to blame.
A new study reinforces the substance hypothesis, but adds a twist – Betelgeuse himself apparently shone the cloud.
The researchers studied the star in 2019 and 2020 with the NASA icon Hubble Space Telescope. Hubble’s observations from September to November 2019 revealed large amounts of material moving from Betelgeuse’s surface to its outer atmosphere at enormous speeds – about 200,000 km / h (320,000 km / h).
During the three-month-long eruption, Betelgeuse lost about twice as much material to the space of its southern hemisphere as normal, student team members said. (Betelgeuse’s background loss is, in fact, significant – about 30 million times that of our sun.)
This super-hot plasma, like electrically charged gas, cools down considerably after traveling millions of miles of Betelgeuse, condensing into dust grains and forming a light-blocking cloud, the scientists suggested in the new study, published online today ( August 13) in The Astrophysical Journal.
“This material was two to four times more luminous than the star’s normal brightness,” said lead author Andrea Dupree, associate director of the Center for Astrophysics, run by Harvard University and the Smithsonian Institution in Cambridge, Massachusetts, in a statement. .
“And then, about a month later, the southern part of Betelgeuse suddenly damned when the star got brighter,” Dupree said. “We think it’s possible that a dark cloud resulted from the outflow that Hubble discovered.”
Additional Hubble observations support this interpretation. Ultraviolet light data showed that Betelgeuse’s outer atmosphere was back to normal until February 2020, even though the floor deepened in visible wavelengths.
It is unclear what caused the fall of 2019. But Dupree and co-author Klaus Strassmeier, of the Leibniz Institute of Astrophysics Potsdam in Germany, think it was probably abducted by regular pulsations from Betelgeuse.
The supergiant star expands and contracts on a 420-day cycle. Strassmeier measured the velocity of gas on the surface of Betelgeuse with an automatic telescope at the Leibniz Institute and found that the eruption occurred during the star’s expansion phase.
Dupree plans to continue studying with Betelgeuse with Hubble, and other astronomers will no doubt also keep tabs on the star. The supergiant is interesting enough in its current state, and observations of it would assume even more importance if Betelgeuse went boom in the very near future.
“Nobody knows what a star does just before it goes supernova, because it was never observed, “said Dupree. Astronomers have sampled stars, perhaps a year prior to their supernova, but not within days or weeks before it happened. But the chance that the star will supernova at any given moment is pretty small. “
Mike Wall is the author of “Out There” (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.
