Betelgeuse is a red supergiant star, approximately 764 times larger than the Sun and located approximately 548 light years away.
Betelgeuse, also known as Alpha Orionis,is located in the constellation of the same name, in the eastern shoulder of the hunter. Its name comes from the Arabic term bat al-jawzāʾ, which means "shoulder of the giant".
What happened to Betelgeuse recently?
Even an amateur astronomer can easily find Betelgeuse in the sky, due to its brightness and position in the brilliant constellation Orion, as well as its reddish color.
This four-panel chart shows howthe southern region of rapidly developing bright red supergiant star Betelgeuse may have suddenly become dimmer for several months in late 2019 and early 2020. Photo: NASA Hubble
It is a variable star and its apparent magnitude isabout 0.6. However, at the end of 2019, it began to fade. By early 2020, visibility was at 1.6, and later that year, it returned to its original brightness. This "Great Blackout" (pictured above) is caused by a giant release of gas that condenses into dust as it cools.
But this is not the only change that has happened to the star in her entire history.
How does a star change?
As nuclear fusion progresses at the center of the starits brightness, size and color also change. Studying these properties, astrophysicists can extract important information about the age and mass of a space object. Stars with more mass than the Sun are blue-white or red. At the same time, the transition from the “red stage” to the “yellow-orange” is relatively fast for astronomical time scales.
Astrophysicists at Jena UniversityFriedrich Schiller, Germany, together with colleagues from the USA and Italy, just recorded and dated such a color change in Beteltgeuse. With the help of several historical sources, they found that this star was yellow-orange about 2,000 years ago. They report their results in the current issue of the Monthly Notices of the Royal Astronomical Society.
Historical data on Betelgeuse
Around 100 BC e.Chinese court astronomer Sima Qian wrote about the colors of the stars: “white - like Sirius, red - like Antares, yellow - like Betelgeuse, blue - like Bellatrix.” Based on these characteristics, scientists concluded that at that time Betelgeuse's color was between the blue-white of Sirius and Bellatrix and the red of Antares, explains Professor Ralf Neuhäuser of the University of Jena.
Regardless of the observations of the Chinese astronomer,100 years later, the Roman scientist Hyginus compared the color of Betelgeuse to the yellow-orange hue of Saturn. This provides further evidence that the color of the star has changed over 2,000 years.
Scientists also studied the records of Ptolemy. According to his observations, at one time Betelgeuse did not belong to a group of bright red stars such as Antares (in the constellation Scorpio) and Aldebaran (in Taurus).
Photo: Pablo Carlos Budassi, CC BY-SA 4.0, via Wikimedia Commons
The Greek name Antares means "like Mars" and the star has been compared to the Red Planet for millennia in cultures around the world.
When will she explode?
Astronomer Ralf Neuhäuser for the last 10years included historical astronomical observations in his astrophysical research. He collaborated closely with fellow philologists, historians and natural philosophers. “There are many astrophysical problems that can hardly be solved without historical observations,” the scientist explains.
Thus, according to historical data on the changecolors for two millennia from yellow-orange to red and theoretical calculations about its mass, which is 14 times greater than the sun, the death of a star will come soon enough (on a cosmic scale). Now Betelgeuse is 14 million years old, and it is at a late stage of evolution. In about 1.5 million years, it will finally explode as a supernova.
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Cover photo: Betelgeuse Alfa Orionis nebula. Giuseppe Donatiello