Astronomers are puzzling over an extraordinary period of weakness for the Red Giant Betelgeuse in the constellation Orion. The brightness of the giant sun has more than halved since October. The exact cause of the sharp drop in brightness is not known, explained the star researcher Thomas Janka from the Max Planck Institute for Astrophysics in Garching near Munich.
The scientist does not see the phenomenon as a sign of an impending supernova explosion of the star, which had been speculated on the Internet. Betelgeuse forms the shoulder of the sky hunter Orion and is the second brightest star of this constellation. It can be seen with the naked eye as a bright red dot. The giant star has about twenty times the mass and around a thousand times the diameter of our sun.
The brightness of the red giant fluctuates in two irregular cycles, each lasting almost six years and approximately 425 days. “We don’t know exactly what is the variability of Betelgeuse,” said Janka. Possibly clouds of matter blown from the star into space temporarily swallowed the light of the giant sun.
In December, researchers led by Edward Guinan from Villanova University in the USA reported the lowest brightness of Betelgeuse since the first such measurements were made almost a hundred years ago. The striking period of weakness seems to stem from the fact that both observed activity cycles of the star have reached an unusually deep minimum at the same time, the researchers wrote in “Astronomer’s Telegram”.
Since Betelgeuse burns up its supply extremely quickly, the red giant has a comparatively short life expectancy: although it is only about eight million years old, it will soon explode as a supernova. Soon, however, means on an astronomical scale sometime in the next 100,000 years. Since Betelgeuse is only about 600 light years away, this supernova is estimated to be as bright in the earthly sky as the full moon and also visible during the day.
Speculation had interpreted the now observed extraordinary loss of brightness as a possible harbinger of such a supernova. According to Janka, however, this is not plausible. The reason is a decoupling of the star shell from its core. “The brightness of the shell is independent of the core,” said the astrophysicist. If there is any noticeable change at all, it is more likely that the red giant will brighten before a supernova explosion. “Betelgeuse is a candidate for supernova, but it is currently not possible to predict when it will happen,” said Janka. “It can happen in a few years, in a few centuries, or in a few millennia.”
Betelgeuse may be the tenth brightest star in the earthly firmament, depending on the fluctuation in activity, and has inspired numerous authors, among others. In the novel series “Hitchhikers Guide to the Galaxy”, Betelgeuse is the home system of the protagonists Ford Prefect and Zaphod Beeblebrox. On a fictional planet around Betelgeuse, Pierre Boulle’s multi-screened book “The Planet of the Apes” also plays. And the German writer Arno Schmidt refers to Betelgeuse in the physical treatises of his story “Leviathan”. (Apa / dpa)
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