Betelgeuse 2: the star of the supergiants is unlikely to explode because of a parasite!

If you say her name three times, be careful, because she could explode in a sky-shattering supernova, perhaps ending in an extraordinary neutron star. Or, more mischievously, she would suddenly hide behind a huge veil of dust to almost disappear.

Betelgeuse is perhaps the most famous star after the Sun. And for good reason, it is at least 750 times larger than the latter, perhaps even 1000 times! Imagine it in our solar system: we Earthlings would be inside the star. Indeed, the radius of Betelgeuse goes approximately as far as Jupiter and the first five planets would therefore be engulfed in the envelope of this somewhat degenerate queen, whose color of dress indicates that she is in the final phase of her life.

It is often presented as one of the most likely stars to explode soon, but wrongly according to some specialists of the red supergiant, such as Miguel Montarges.

Here's a recent simulation of Betelgeuse's bubbling surface, which is so swollen that it's no longer even spherical:

Betelgeuse is also famous for being one of the brightest stars in the night sky. Like a ruby, it sparkles and sits enthroned in the winter sky where we almost only see it and its fascinating and capricious garnet color. Capricious, it is, because like a diva, it is a variable star, that is to say whose luminosity is not regular over time, oscillating and pulsing over a period of 400 days . Sometimes it is the 7th brightest star in the sky, sometimes the 11th, or even much less.

Betelgeuse often varies, but who trusts it?

But while the whole world watched, stunned, at the beginnings of the Covid pandemic at the end of 2019, the astronomy community looked towards its sulking diva: Betelgeuse was gradually disappearing! Of course, he had mood swings, but never like that winter when his brightness very suddenly diminished. Betelgeuse ultimately became the 21st brightest star. It's a bit as if Albert Einstein, or Cédric Villani, had come home from school with a 13/20 in mathematics.

Shock and trembling: will Betelgeuse explode?!

Speculation was rife at the time, even if the specialist at the Paris Meudon observatory, Dr. Montargès, very quickly had the intuition, then the certainty, that the most famous supergiant was not going to explode soon, the star was just acting up again.

The cause of this new mystery was found: a gigantic veil of dust, probably ejected by the supergiant itself, passed between it and us. The star regained its brightness, the bloodshed was over. After the obscuration came the time to shed light on this strange astronomical event.

In addition to its well-known and documented pulsation period of 400 days, astrophysicists therefore calculated a second, longer period (LSP) of around 2100 days. A debate followed, which is still lively today, to determine what is the “fundamental” mode of the star. Is it the short or the long? Answering this question could change everything whether or not its inevitable explosion occurs soon.

A Betelbuddy for Betelgeuse would be the best explanation!

The study in question today, available on arXivsuggests that the superstar has a shadowy companion who would be the cause of this long and enigmatic period. Behind the great lady would therefore hide a little man, understand another star. In short, Bételgeuse would be in a relationship, which would explain this second apparent mode of pulsation.

The researchers called it Ori b (yes, like an exoplanet orbiting Betelgeuse) and estimate its mass to be between 1 and 2 solar masses (≈1.17 more likely). Its orbit would have a slight inclination compared to our line of sight and would be located approximately 1800 solar radii from the supergiant, or approximately double its own radius.

Is this companion a neutron star?

But what is the nature of this companion star? Based on our knowledge of how massive stars form, the possibility that Betelgeuse was born with an even more massive sister that has since exploded is real. Except that given its inferred mass (≈1.17 solar masses), its residue would be a neutron star or a white dwarf. That said, a neutron star would involve bursts of X-rays that we have not yet observed. One of the authors specifies that in his opinion, this possibility should not be eliminated before a specific observation campaign.

The nature of this companion is crucial in determining the time remaining in Betelgeuse before lighting up the earth's sky like a rock star, a bit (much) like in 1181. At the end of the article, the authors propose several avenues for observing and detecting this famous companion to the most famous winter star.