In recent weeks, changes in the star’s appearance have been bringing astronomers around the world to a boil.
She is a bit pale. The giant star Betelgeuse, one of the brightest in the Milky Way, has been scrutinized by the largest telescopes on the planet, since its luminosity has dropped “drastically, around 70%”, explains Pierre Kervalla, of the Paris Observatory, to AFP. Scientists hope to have the chance to witness the extremely rare spectacle of its supernova explosion. We will explain what is happening to Betelgeuse.
What is Betelgeuse?
Betelgeuse is a star at the end of life which is located in the constellation of Orion, “700 light years from us”, precise Eric Lagadec, astrophysicist at the Côte d’Azur observatory, vice-president of the French Society of Astronomy and Astrophysics. This super giant red, almost a thousand times larger than the Sun, shines brightly in the winter sky, where it is visible to the naked eye and easy to spot thanks to its orange color. The star was among the 10 brightest in the galaxy. “If it were in the center of our Solar System, its radius would exceed that of the asteroid belt, located between Mars and Jupiter. In reality, it is a variable star [une étoile dont la luminosité varie dans le temps]. It expands and contracts, and its radiance varies in several cycles, which combine over time “, details astrophysicist Sylvie Vauclair for Futura Sciences.
Astonishing: Betelgeuse in comparison to our solar system.
It is so incredibly immense that if swapped with our Sun it would engulf the orbit of Mars!
Credit: ESO / L. Calçada pic.twitter.com/hAIdJppaqo
– Universal-Sci (@universal_sci) February 10, 2020
What is happening to him?
Since fall 2019, it shines much less. “The brightness of the star has dropped on half of its apparent surface”, Described to AFP Miguel Montargès, astrophysicist at the Catholic University of Louvain, in Belgium. “Since the end of October, the brightness of Betelgeuse has dropped from 60 to 70% which is quite unusual, details Pierre Kervalla at Parisian. Normally, its brightness does not vary by more than 20% “. “The current drop in brightness is much steeper than usual. It is therefore legitimate to be concerned about it”, assures Sylvie Vauclair.
How is that explained?
There are several theories, but none can be advanced with certainty at this time. The most spectacular being that the star is close to turning into a supernova. Born about eight million years ago, the star at the end of its life having no more “fuel” (resulting from nuclear fusion), its heart would collapse on itself and would form a neutron star, a very compact object that creates a shock wave completely dislocating the star, in just a few hours.
I photographed various nearby bright stars to compare to #Betelgeuse on 20 December. I estimated it at less than mag 1 but see what you think. Same settings used for all and defocused to bring out the colors. #astronomy #Astrophotography #Orion #stars #space @VirtualAstro pic.twitter.com/u7Ma1XgV6S
– Steve Brown – astronomer ✨ (@sjb_astro) December 30, 2019
This attractive theory, all astronomers dream of it. “It’s boiling! We have set up a research group around the world to use all the instruments capable of imaging the surface of Betelgeuse (…) It would be an unforgettable spectacle for all of humanity. hope i can see a supernova in my lifetime “, says Eric Lagadec. “But this is not the case”, does he temper the Parisian.
Observations were made and “We found that half of the star’s hemisphere was dark. So something happened, but it’s not a sign of a supernova”, he says. “Two interpretations are possible: either the surface has cooled, and it has therefore become more obscure, or gigantic heaps of dust have formed between us and the star. This dust, to put it simply, are small grains of a thousandth of a millimeter that wander in clouds “, he explains.
Why would a supernova be an event?
A supernova explodes on average every 100 years in the Milky Way, according to astronomers, but the last formation of supernova observed dates back to 1604. It was Kepler’s supernova, recalls Futura Sciences. The first account of the death of a star dates back to 1054 in China, recalls The Parisian. The event is described as the presence of “two suns in the sky”. “This second point of light shone for twenty-three days in a clear blue sky”, writes the daily, citing stories from the time.
“With Betelgeuse, the show will no doubt be just as magnificent, believes Pierre Kervalla, because this star is one of the most imposing stellar objects in our galaxy. When it breaks up, the resulting explosion will be visible day and night, for several weeks. We will then see a luminous point settle in the sky, as bright as the Moon. “
However, it is impossible to estimate the date of such an event. “It’s a bit like an earthquake … A star dies in a few hours the day before the explosion, underlines the scientist of the Paris Observatory, it could therefore happen in the coming weeks as in 100,000 years. ” On a scientific level, the event would allow astronomers to follow directly, for the first time in history with sophisticated equipment, the different phases of the explosion, a precious gauge to measure the expansion of the Universe. “We would also understand what will happen to the future generation of stars”, Concludes Andrea Chiavassa, CNRS astrophysicist at the Lagrange laboratory of the Côte d’Azur Observatory.
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