Betelgeuse is one of the brightest stars in the sky located in the should of the constellation Orion. Astronomers were giddy with excitement as they experienced the Great Dimming in 2019, which signals that it is at the end stages of its life.
According to Britannica, the Great Dimming was due to an enormous surface mass ejection (SME) that condensed into dust after it cooled. Betelgeuse is easy to spot by a casual observer because of its brightness and deep reddish color. This red supergiant star is almost 764 times bigger than the Sun and is located 546 light-years from Earth.
This image is a colour composite made from exposures from the Digitized Sky Survey 2 (DSS 2). The field of view is approximately 2.0 x 1.5 degrees.
Betelgeuse 2,000 Years Ago
Sima Qian, a Chinese historian of the early Han dynasty (206 BC-AD 220), described the Betelgeuse star in one of his texts 2,000 years ago. Unlike today, he did not see a crimson star on Orion's shoulder but instead found a yellow star. Modern astronomers said that Sima Qian's observations were right, this could mean that the star's evolution has been serendipitously witnessed.
Scientific American reported that Sima Qian's report is just one of many historic observations that pin down the age of Betelgeuse at 10 million years with a mass that is 14 times that of the Sun. Knowing a star's mass and color is important to know how they would evolve.
The paper, titled "Color Evolution of Betelgeuse and Antares Over Two Millennia, Derived From Historical Records, as a New Constraint on Mass and Age Get Access Arrow" published in the Monthly Notices of the Royal Astronomical Society, said that color adjustments by a few millennia suggest that Betelgeuse could have another million years before it would collapse and explode.
The authors of the paper have looked at data from historians, astronomers, and astrologers from the Northern Hemisphere and created a distinctive 2,000-year timeline of Betelgeuse's evolution to track down its development from being a yellow star like the Sun into the purple star seen today.
But whatever the color of Betelgeuse 2,000 years ago, the sure thing is that it is now purple due to the nuclear fusion reactions that have burned away virtually all of its hydrogen at its core. The star now burns extra-rich helium gas, while its surface gas becomes ruddy from the additional warmth.
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Decoding Historic Observations of Betelgeuse
Catching the metamorphosis of a star or what scientists call the "crossing the Hertzspurg gap" is not easy as such episodes are fleeting. A star could shine for tens of billions of years and then cross the Hertzspurg gap in a few thousand years. The process is considered virtually instantaneous on cosmic scales, but it is an infinite span of time for humans.
Tracking down historic observations and decoding the meanings of phrases from different centuries and cultures is just one of the challenges the scientists faced. Additionally, they considered the impression of mud in Earth's ambiance and interstellar area that might have affected the color of the starlight. They even analyzed the anatomical structure of the human eye that impacts coloration notion.
Historic records also do not put Betelgeuse in the list of purple stars, which can be seen by bare eyes. Considering that Betelgeuse is one of the many brightest and reddest stars in the sky now, not seeing it in the list of purple stars during the time of the Greek polymath Ptolemy means that it was not purple.
Despite the challenges of decoding historic observations of Betelgeuse, astronomers said that the historic time strains provide a beneficial contribution to the analysis and understanding of the evolution of stars.
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