Betelgeuse is 25 percent closer than previously thought

James Marshall
October 18, 2020

Scientists previously estimated this to be the size of Betelgeuse relative to our solar system, but a new study corrected that estimate.

Betelgeuse is a red supergiant and monstrous compared to the size of our sun. But it's been acting unusual lately.

Betelgeuse caught the attention of astronomers when it dimmed and brightened in late 2019.

Scientists previously thought a year ago that Betelgeuse was on the verge of exploding as it became noticeably dimmer (at least, it was noticeable from an advanced telescope). However, our study offers a different explanation. "We found that the second minor event was likely due to the star's pulsations".

"We know that the first dimming event involved a cloud of dust".

The astronomers wanted to investigate Betelgeuse using physical models of how gas flows inside the star, and how seismic waves travel through it, because these depend on the internal structure of the star (a little like how seismic waves traveling through the Earth tell geologists about the structure inside our planet).

"Right now, helium is burning at its core, which means it is nowhere near exploding", said Dr. Joyce.

"We could be looking at around 100,000 years before an explosion happens".

The scientific team used modeling to sort out what was going on with the pulses, discovering what co-author Shing-si Leung of the University of Tokyo described as "pressure waves - basically, sound waves". "Petalgeus' true body size was a mystery - previous studies have suggested that it may be larger than Jupiter's orbit".

Her co-author Dr Laszlo Molnar from the Konkoly Observatory in Budapest explained how the study also revealed the size of Betelgeuse and its distance from Earth.

For example, its size, mass, age, and distance are all extremely hard to determine.

By better sizing the Betelgeuse, the team more accurately calculates its distance to Earth, located at a distance of about 530 light-years, which is about 25% closer than previously known. That is still far enough that Betelgeuse's future explosion will not harm the earth.

"It's still a big deal when a supernova goes off". It's our closest candidate. "It gives us a rare opportunity to study what happens to stars like this before they explode", added Dr Joyce.

The study was funded by the Kavli Institute for Physics and Mathematics of the Universe (WPI) at the University of Tokyo and supported 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.

More information: Meridith Joyce et al. Except for fair trade for the objective of private study or research, no part may be reproduced without written permission.

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