Drastic change: New telescope images confirm the dramatic darkening of the red supergiant Betelgeuse – it has lost two thirds of its luminosity within a year. In addition, the images reveal huge clouds of dust around the star. It is still unclear whether these are signs of its impending explosion or just symptoms of temporary processes.
The star Betelgeuse, which is only 700 light years away, is hard to miss in the night sky – it forms the left shoulder star of Orion. Astronomers have long suspected that this red supergiant is nearing the end of its life cycle and will soon be in a supernova could explode, But in the past year, Betelgeuse has dramatically changet: The once bright star lost two thirds of its brightness within a year – this obscuration is even visible to the naked eye in the sky.
Darkening is not even
Now pictures of the surface of Betelgeuse confirm these drastic changes. A team led by Miguel Montargès from the Catholic University of Leuven used the Very Large Telescope (VLT) of the European Southern Observatory (ESO) in Chile to take a closer look at the red giant. “The ESO Paranal Observatory is one of the few facilities able to map the surface of Betelgeuse,” explains Montargès. “This is the only way we can understand what is happening to the star.”
The new photographs in visible light show how much the surface of the red supergiant has darkened. Compared to a picture taken in January 2019 with the same telescope, the star appears to be very dim. In addition, its surface is no longer uniformly bright, but is characterized by lighter and darker areas, as astronomers report. Betelgeuse seems to have almost changed its shape as a result.
Surrounded by large clouds of dust
Current insights in the mid-infrared range, taken by the VISIR spectrometer on the Very Large Telescope, provide further insights. They make huge dust clouds visible in the area around Betelgeuse. These clouds of dust were most likely thrown out by the waning star. That suggests that astronomers already in 2011 have detected large amounts of silicate and aluminum dust in the area of Betelgeuse. This dust probably comes from the outer shell of the star.
“Red giants like Betelgeuse create huge amounts of material in their lifetime and emit it before they explode as supernovae,” explains Emily Cannon from KU Leuven. In just 10,000 years, a star can lose as much mass as is contained in our sun.
What is the reason?
But what does this mean specifically? Could this herald an impending Betelgeuse explosion? Montargès and his team are rather skeptical in this regard. They do not yet consider the current changes in the star to be symptoms of an impending supernova. Instead, they look for other explanations. “The two scenarios we are working on are cooling the surface due to an unusual star activity or by ejecting dust in our direction,” says Montargès.
So far, which of these scenarios is correct is still unclear – and the future of the weakening star remains uncertain. “Of course, our knowledge of the red supergiants is still incomplete, and this is still the subject of intensive research so that there can still be surprises,” admits Montargès.
Source: European Southern Observatory (ESO)
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