Betelgeuse supergante rouge behaves strangely smaller and closer than first thought


Illustration of Betelgeuse. Credit: NASA, ESA and E. Wheatley (STScI)

It may be another 100,000 years before the giant red star Betelgeuse dies in an explosion of fire, according to a new study by an international team of researchers.

The study, led by Dr Meridith Joyce of The Australian National University (ANU), not only gives Betelgeuse new life, but shows that she is both smaller and closer to Earth than previously thought.

Dr Joyce says the supergiant – who is part of the constellation Orion – has long fascinated scientists. But lately he’s behaving strangely.

“It is normally one of the brightest stars in the sky, but we have observed two drops in the brightness of Betelgeuse since the end of 2019,” said Dr Joyce.

“It sparked speculation that was about to explode. But our study offers a different explanation.

“We know the first gradation event involved a cloud of dust. We found out that the second smaller event was likely due to the star’s pulses. ”

The researchers were able to use hydrodynamic and seismic modeling to learn more about the physics behind these pulses – and get a clearer idea of ​​the phase of his life in Betelgeuse.

According to co-author Dr Shing-Chi Leung of the University of Tokyo, the analysis “confirmed that pressure waves – essentially sound waves – were the cause of the Betelgeuse pulse.

“It’s burning helium in its nucleus right now, which means it’s far from exploding,” Dr. Joyce said.

“We could look at around 100,000 years before an explosion occurs.”

Co-author Dr. László Molnár from the Konkoly Observatory? In Budapest says that the study also revealed the size of Betelgeuse and its distance from Earth.

“Betelgeuse’s actual physical size has been a bit of a mystery – previous studies suggested it could be larger than the orbit of Jupiter. Our results indicate that Betelgeuse only extends two-thirds of that, with a radius of 750 times the sun’s radius, ”said Dr Molnár.

“Once we had the physical size of the star, we were able to determine the distance from Earth. Our results show that we are only 530 light years away from us – 25% closer than previously thought.

The good news is that Betelgeuse is still too far from Earth for the eventual explosion to have a significant impact here.

“It’s always a really big deal when a supernova goes off. And this is our closest candidate. It gives us a rare opportunity to study what happens to stars like this before they explode, ”said Dr Joyce.

The study was funded by the Kavli Institute for the Physics and Mathematics of the Universe (WPI), the University of Tokyo, and facilitated by the ANU Distinguished Visitor’s program. It involved researchers from the United States, Hungary, Hong Kong and the United Kingdom, as well as Australia and Japan.

The study was published in The astrophysical journal.

Reference: “Standing on the Shoulders of Giants: New Mass and Distance Estimates for Betelgeuse Using Evolutionary, Asteroseismic and Hydrodynamic Simulations Combined with MESA” by Meridith Joyce, Shing-Chi Leung, László Molnár, Michael Ireland, Chiaki Kobayashi and Ken’ichi Nomoto, October 13, 2020, The astrophysical journal.
DOI: 10.3847 / 1538-4357 / abb8db


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