The star Betelgeuse is relatively close to Earth – and it should soon explode as a supernova. Whereby astronomers have a slightly different definition of soon.
Astronomers are puzzled about an unusual 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 the variability of Betelgeuse is, Janka explained. 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 United States reported the lowest brightness of Betelgeuse since the first such measurements almost a hundred years ago. The striking period of weakness seems to stem from the fact that both observed activity cycles of the star had reached an unusually low minimum at the same time, the researchers wrote in the 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 in astronomical masts 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 unusual loss of brightness now observed 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 nucleus, explained 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 when it is time is currently not clear, Janka explained. It can happen in a few years, in a few centuries, or in a few millennia.
Betelgeuse can be the tenth brightest star in the earthly firmament, depending on the fluctuation in activity, and has inspired numerous authors, among others. In the series Hitchhiking through the Galaxy of Douglas Adams, Betelgeuse is the home system of the protagonists Ford Prefect and Zaphod Beeblebrox. On a fictional planet around Betelgeuse, Pierre Boulle’s multi-filmed 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.
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