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Strange Behavior of Red Supergiant Betelgeuse Smaller and Closer to First Thought

Betelgeuse Illustration

Description of betelgeuse. Credits: NASA, ESA, and E. Wheatley (STScI)

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

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

Dr. Joyce that the supergiant – part of the constellation of Orion – has long fascinated scientists. But lately, it has behaved strangely.

“It’s usually one of the brightest stars in the sky, but we’ve observed two drops in Betelgeuse’s radiance since late 2019,” said Dr. Joyce.

“It prompted speculation that it might explode. But our study offers a different explanation.

“We knew that the first dimming event involved a dust cloud. We found the second smaller event was probably due to star pulsations.”

Researchers have used hydrodynamic and seismic modeling to learn more about the physics that drive these pulses – and get a clearer idea of ​​what stage of its life Betelgeuse is.

According to fellow author Dr. Shing-Chi Leung from The University of Tokyo, the analysis “confirmed that the pressure gauges – the important, sound waves – were the cause of the Betelgeuse bug.”

“It’s burning helium in its core right now, which means it’s nowhere near the explosion,” said Drs. Joyce.

“We can look around 100,000 years before an explosion occurred.”

Co-author Dr. László Molnár from Konkoly Observatory? In Budapest the study also said that it also revealed how big Betelgeuse is, and how far it is from Earth.

“Betelgeuse’s actual physical size has become a mystery – previous studies have suggested that it may be larger than the orbit of Jupiter. Our results say that Betelgeuse only reaches two-thirds of it, with a radius of 750 times the radius of the sun, “said Dr. Molnár.

“When we had physical star size, we determined the distance from Earth. Our results show that it was a little 530 light years from us – 25 percent closer than previously thought.”

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

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

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

The study is published in The Astrophysical Journal.

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

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