2023-10-14 05:40:31
It is a massive red star, which forms one of the shoulders of the hunter in the constellation Orion: it is dying, but this is the first time that a study has affirmed that its end in supernova is very close, or even already arrived. The image and the information have simply not reached us yet.
Betelgeuse is one of the best-known red supergiants in the cosmos: it is located in the constellation Orion. For a long time, astronomers have known that this star – whose radius is close to a thousand times that of our Sun – is probably at the end of its life.
The constellation of Orion and its nebulae. At top left, the very bright star is the red supergiant Betelgeuse. [Stanislav Volskiy/Judy Schmidt – NASA]At the end of September, an international team including astrophysicists from the University of Geneva (UNIGE) showed that the star is at a stage approaching its final supernova explosion: “If our calculations are correct, Betelgeuse would have already exploded”, says Georges Meynet, professor in the Department of Astronomy at UNIGE and co-author of the study to appear in the Monthly Notices of the Royal Astronomical Society. “Simply, the signal showing us that Betelgeuse has exploded is still traveling towards us,” he explains in the CQFD program.
Betelgeuse is in fact regarding 650 light years away from us and, as light travels at 300,000 kilometers per second, it takes some time for the information to reach us: “The light we observe today on Earth departed from Betelgeuse 650 years ago. Our calculations indicate that Betelgeuse may have exploded when we on Earth were between the years 1373 and approximately 300 years later, or 1673.”
The astrophysicist specifies that, as the signal of the star’s explosion takes 650 years to reach us, “it will reach us between now and the year 2300 or 2350”, or at the latest in 300 years. A journey through time: we will see an explosion that occurred between the 14th and 17th centuries. It will be as bright as the full Moon and it will be possible to see it in broad daylight.
A few hundred or a few decades?
Until now, studies looking at the remaining lifespan of Betelgeuse estimated that it might still shine for a few hundred thousand years, taking into account the fact that the star had already lived around eight million years. years since training (read box).
However, the Geneva research team reanalyzed the signals emitted by the star and showed that the time it has left to live might therefore be much shorter: at most a few hundred years, or even only a few dozen years. years! “A prediction which has uncertainties”, Georges Meynet is quick to point out: “A model tries to make the most of everything we know, but everything we know is not always sufficient to be more affirmative, accurate”.
>> Listen to the explanations of Professor Georges Meynet (UNIGE) in CQFD: The star Betelgeuse might explode in a supernova faster than expected / CQFD / 10 min. / September 29, 2023
A beating heart
To arrive at this shorter estimate of Betelgeuse’s lifespan, scientists analyzed the variability of its brightness over time: “It’s a bit like a beating heart: it increases and decreases in radius with periods which can be different from each other and which can overlap.
The longest pulsation period lasts 2200 days and the shortest around 200 days: “There are two others with intermediate periods. The idea is to build models that make it possible to reproduce the luminosity, the color of Betelgeuse and its pulsation periods. What changed from previous work is that the longest period – that of 2200 days – was not considered a physical pulsation of the star. It was due to another perceived phenomenon like a little obscure. We took this period of pulsation seriously, trying to see if we might reproduce it and reproduce the other three shorter ones.
And their model has in fact reproduced the four observed pulsations of Betelgeuse, as well as its luminosity and its color: “And contrary to those who have ruled out this longer pulsation, we obtain a very advanced stage in the evolution of the star, very close to its final stage. This mechanism is linked to a physical phenomenon: “It is also quite well understood and is generated by the star itself”.
“Our model is a model and also has its weaknesses. I don’t know if we are right, but we have serious arguments,” concludes Georges Meynet. Don’t forget to take a look at Orion: a unique spectacle can occur at any time.
Radio interview: Anne Baecher and Bastien Confino
Web article: Stéphanie Jaquet
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