The star Betelgeuse, in Orion, was still yellow 2,000 years ago!

If the star Betelgeuse currently appears red to the naked eye, it has not always been the case. Researchers have just demonstrated that its transformation into a red supergiant took place very recently, and that it was still a yellow star 2,000 years ago!

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[EN VIDÉO] Why does the star Betelgeuse change in brightness?
Who is Betelgeuse, a usually very bright star in the constellation of Orion. Why has its luminosity been steadily decreasing since the fall of 2019? What will happen to him?

During its evolution, when the star has consumed all its fuel and can no longer perform nuclear fusions, it then passes to the next stage which depends on its initial mass. Lstar Betelgeuseanalyzed in a study in the journal MNRAS, is no exception. She is currently at the stage of red supergiantthat is to say, it came out of the main sequence and will become a supernova in a very short time on an astronomical scale.

While she has already surprised during her decrease in luminosity in 2019the second brightest star in the orion constellation has interested researchers for something else: its color. If it currently appears red, the team has just demonstrated that this has not always been the case! Ancient texts, ranging from three millennia ago to today, show that “Betelgeuse evolved rapidly in color as it crossed the Hertzsprung-Russell diagram”explains the study, that is to say that it was still yellow 2,000 years ago!

This type of evolution is rarely observable on a human scale.

Whether in writings of the Chinese court Sima Qian in 100 BC. J.-C., or in accounts of “Mediterranean Antiquity (Hyginus, PtolemyGermanicus, Manilius and Cleomedes)”, Betelgeuse is described 2,000 years ago as being similar in color to Saturnor just yellow. “From these specifications, it can be concluded that Betelgeuse at that time was colored between the blue-white of Sirius and Bellatrix and the Red of Antares”Explain Ralph Neuhauser in a communicatedfirst author of the study and professor at the University of Jena.

A data that may seem insignificant but which is important. “The very fact that it changed color in two millennia from yellow-orange to red tells us, with theoretical calculations, that it has 14 times the mass of our Sun — and mass is the main parameter defining the evolution of starsexplains R.Neuhäuser. Betelgeuse is now 14 million years old and in its final stages of evolution. In about 1.5 million years, it will finally explode as a supernova”.

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