Watching on as Betelgeuse dims

Astronomers have captured new images of the unprecedented dimming of Betelgeuse, a red supergiant star in the constellation of Orion.

Taken using the European Space Observatory’s Very Large Telescope (VLT), they confirm what the eye suggests – that it is down to about a third of its normal brightness – and reveal how its apparent shape is changing.

But it’s probably not about to explode, according to the team that has been observing it closely since December.

Like all red supergiants, Betelgeuse will one day go supernova, but Miguel Montargès, from KU Leuven in Belgium, and his colleagues have other hypotheses to explain what exactly is happening now. 

“The two scenarios we are working on are a cooling of the surface due to exceptional stellar activity or dust ejection towards us,” he says. “Of course, our knowledge of red supergiants remains incomplete, and this is still a work in progress, so a surprise can still happen.”

Instruments on the VLT, at Cerro Paranal in Chile, allow observations from the visible to the mid-infrared, meaning astronomers can see both the surface of Betelgeuse and the material around it. 

“This is the only way we can understand what is happening to the star,” Montargès says.

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