Betelgeuse is smaller and closer than previously thought, but it won’t explode anytime soon


Betelgeuse, one of the brightest stars in the night sky, caught the attention of scientists by showing a decrease in brightness in late 2019. This behavior could mean that the star was advancing into the final stages of its evolution and could explode in a supernova . That didn’t happen, and now a new study suggests that the star still has at least 100,000 years to live.

There is much expectation that a nearby star will become a supernova, as this is a relatively rare event. Stars can shine for billions of years before entering degeneration processes (loss of the qualities of a star), and our stay on Earth is quite short compared to cosmic time. To witness a supernova being born from the beginning would be a unique opportunity for scientists to learn more about our universe.

So Betelgeuse was expected to explode in a supernova, but in early 2020 the analysis shattered astronomers’ hopes by revealing that the star was already recovering its brightness and that the strange behavior was the fault of a dust cloud. In August 2020, something different happened there again, but this time the scientists concluded that they were detecting the star’s own natural pulse.

Now, a new study suggests that some things we knew about it were wrong: the star is smaller and closer to us than previously estimated. The research also points out that she still has a lot of fuel to burn before entering the final stage of her life.

Artistic concept showing the course of the Betelgeuse dust eruption, which caused the star’s apparent decrease in brightness (Image: NASA / ESA / E. Wheatley (STScI))

The study was led by Dr. Meridith Joyce of The Australian National University (ANU) and published in the Astrophysical Journal. The team used hydrodynamic and seismic modeling to understand the physics that led to the pulsations that caused the star’s brightness to decrease and to find out what stage of its evolution Betelgeuse is in. Thus, they found that the pulse was caused by “pressure waves – essentially sound waves”. They also found that the star “is burning helium at its core right now, which means it is nowhere near exploding,” explained Joyce.

Another aspect analyzed by the study was the distance from the star, which was better determined once the team was able to better calculate its size. Dr. László Molnár, from the Konkoly Observatory in Budapest, explained that the physical size of the Betelgeuse was somewhat mysterious to date, with some studies suggesting that it would be larger than Jupiter’s orbit. “Our results say that Betelgeuse extends only two-thirds of that, with a radius of 750 times the radius of the Sun,” said Molnár.

With size in hand, the team was able to measure distance more easily, and concluded that Betelgeuse “is only 530 light years from us – 25% closer than previously thought”. Still, it is far enough away that an eventual explosion does not affect our planet.

If these results are correct – and more research is likely to be done to confirm this – the study will have a very positive impact. Getting away from Betelgeuse is very difficult and getting it right is impressive. The problem with this star is that its brightness is too intense for observatories like ESA’s Gaia to observe, and other methods result in different values. But the 530 light-year result is consistent with the old measurements from the Hipparcos satellite, for example.

This does not necessarily mean that the study is correct. Scientists are not unanimous on many issues, and this is one of them. Even the methods used for a study can be controversial, and debates about the new work must take place. This is good, because the more the topic is the subject of interest and scientific debate, the more chances we have of reaching more conclusive results.

Fonte:, Bad Astronomy

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