A simulation questions what we know about Betelgeuse, our closest star that could explode in a supernova!
Betelgeuse was known as the eighth brightest star in the sky AstronomersAstronomers since ancient times. Like many of the stars that delimit the contours of Orion’s constellation in which it is located (Mintaka, Alnilam, Alnitak, Rigel, and Seph), it the doorthe door Name of Arabic origin following the translation into Latin of Arabic astronomical works.
But what astronomers didn’t discover until the first half of the 20th centuryE century, is that Betelgeuse is a monster more than a billion kilometers in diameter, so about 1,000 times the size of the Sun that if it were in its place in the Solar System it would orbit its upper layers. JupiterJupiter.
Betelgeuse was one of the first stars whose diameter we were able to determine in the 1920s, thanks to the technique ofInterferometryInterferometry Also employed by Albert Abraham Michelson and Francis Pease telescopetelescope Hooker from the Mount Wilson Observatory confirmed the method proposed by the Frenchman Hippolyte Fizeau.
Michelson, PhysicistPhysicist In the United States, of Polish Jewish descent, had long ago made a name for himself in the company of Edward Morley by his famous experiment, intended to illuminate the motion of the earth.EtherEther and which was later interpreted as proof of the principle of RelativityRelativity NoEinsteinEinstein (He himself was not aware of this experience when he discovered his theory). For that he was also a Nobel Prize winner PhysicalPhysical 1907.
The video takes the viewer through the constellation Orion to the surface of the red supergiant Betelgeuse, which is currently experiencing an unprecedented decrease in brightness. This dot, seen at the far end of the zoom sequence, is an image of the visible surface of Betelgeuse acquired by the sphere, which has dimensions similar to the orbit of Jupiter. © ESO, P. Kervella, M. Montargès et al., Digitized Sky Survey 2. Acknowledgment: Eric Pantin, N. Risinger (skysurvey.org). Music: Johann B. Monell (www.johanmonell.com)
A unstable variable star that will soon die
Today we also know that Betelgeuse is a Red supergiantRed supergiant Located around 640 at the end of his life light yearslight years of earth and with groupgroup About ten times that of the Sun.
It is very interesting AstrophysicistsAstrophysicists Because it gives us the key to understand more precisely how such very massive stars end their lives after only a few million years.
Indeed, we have known for decades that there is a relationship between a star’s mass, its brightnessbrightness and its lifetime. The more massive the star, the higher the temperature at its core. Consequently, the specific reactions of MergerMerger Thermonuclear is possible, releasing enormous amountsEnergyEnergy required for production pressurepressure Able to oppose it with its own consequences GravityGravity of you
In doing so, it uses up its thermonuclear fuel at such a rapid rate that its lifetime is measured in a few million years rather than billions of years, as is the case with the Sun (for which we hope even ten).
Will Betelgeuse end up in a supernova? A February 2020 revelation from astronomer Miguel Montargues and his colleague Eric Laugadek. © Guillaume Doyen
The theory of star formation and evolution developed by pioneers such as Subrahmany Chandrasekhar and Martin Schwarzschild tells us all this, the latter not just the son of a solution seeker describing simplicity. A black holeA black hole in General relativityGeneral relativity Also one of the pioneers after World War II in use computerscomputers Turing and von Neumann to solve numerically EquationsEquations Description of stellar interiors.
Betelgeuse came out of what we call it main sequencemain sequence By transforming into a red supergiant, it is unstable and although we cannot predict when this will happen, it will explode. SupernovaSupernova – Maybe in a few thousand years. But recently, its decrease in brightness has hit the headlines, as it is believed that the event heralded its imminent eruption. Now we consider an entirely different hypothesis.
A star that spins 100 times faster than expected
Another fact has been questioning astrophysicists for some time. Theory tells us that as it became unstable, Betelgeuse expanded significantly. However, according to one of the fundamental laws of physics, the conservation of A cinematic momentA cinematic moment, Betelgeuse’s rotation should be slower according to the opposite phenomenon which allows the skater to turn faster by folding his arms towards him. Compare with what we know about the orbits of similar stars before formation Red GiantsRed GiantsMeasurements taken, especially with large networks of Radio telescopeRadio telescope no’ESOESO In Chile, famous radio InterferometerInterferometer Alma (Atacama Large Millimeter/Submillimeter Array) with its 66 antennas working together as if they were one A large telescopeA large telescopeIndicates that Bételgeuse is running 100 times faster than expected!
This is a puzzle that may have just been solved by an international team led by astronomers from the Max Planck Institute of Astrophysics, the Lagrange Laboratory (Observatoire de la Côte d’Azur-Université Côte d’Azur-CNRS) and the University of Uppsala, as open Access can be viewed with publication arXiv.
A simulation of the bubbling surface of Betelgeuse. This animation shows how convection dominates the surface of a Betelgeuse-like star. He then shows what this would look like in actual observations of ALMA, highlighting that bubbling surfaces can be mistaken for circulation signatures. © Ma, Jing-Zhe et al, 2024
The article is commented on by a press release from the Observatoire de la Côte d’Azur (OCA) which explains that it is therefore the product of an international team led by Max-Institut doctoral student Jing-Zhe Ma.plankplank NoAstrophysicsAstrophysicsAnd of which Andrea Chiavasa, CNRS researcher at OCA, is a member.
He also explains that the researchers did not take into account the fact that the surface of beteljuice is much more aggressive than the surface of the Sun. movementsmovements Titanic Convection. This movement is similar to that of water heated in a boiling pan. Despite the power of resolutionresolution Alma, the image of the surface of the star remains unclear and measured rotation speedrotation speedusing theDoppler effectDoppler effect Depending on whether the spectral shift occurs towards red or blue mattermatter As the emitted light moves away from or towards the observer, it can be easily interpreted by the observer Convective movementConvective movement And a less significant rotation, this time agreeing with what we initially thought.
Convection cells are as large as Earth’s orbit
To find out for sure, astronomers began conducting simulations of Betelgeuse’s convection, the results of which were submitted in a new. SoftwareSoftware ALMA A post-processing tool developed by researchers to create synthetic images of observations.
As the OCA press release explains, in 90% of the simulations, the observations of the star are not actually interpretable by Betelgeuse’s significant rotational speed but rather as a simulation of the dipole motion map of this rotation raised by the Doppler effect. And so mainly through the large-scale convective activity of the surface of the red supergiant. No is to be told by the bubbles GasGas Creates convective cells that can be as large as Earth’s orbit around the Sun, rising and falling at speeds up to 30 km/s.
The same press release ends by announcing that “ More observations are needed to better assess Betelgeuse’s rapid rotation, and the team predicted future observations with higher spatial resolution. Fortunately, other astronomers have already made high-resolution observations of Betelgeuse in 2022. New data is being analyzed, which will help verify the predictions and reveal the mask of beteljuice.e”
