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Nobody knows what’s going on with the colossal nearby star Betelgeuse

Updated Feb 17th, 2020 8:45AM EST
betelgeuse supernova
Image: ESO/M. Montargès et al.

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One of the more interesting astronomy stories that came out at the tail end of 2019 was the bizarre behavior of the nearby star known as Betelgeuse. It sits somewhere between 520 and 650 light-years from Earth, and that’s extremely close in the grand scheme of things, making its behavior of particular interest to us here on Earth.

Months ago, scientists alerted us to the fact that Betelgeuse is getting dimmer. This massive star is currently a red supergiant, and the fact that it appeared to be dimming hinted at a number of possible outcomes, including a possible collapse and supernova explosion. Now, with several more weeks of observations under their belt, researchers have discovered that Betelgeuse isn’t just dimming, it’s dimming in a very bizarre way.

As Phil Plait of SYFY Wire reports, high-resolution images captured by the Very Large Telescope reveal that Betelgeuse is indeed dimming… but only part of it is actually changing in brightness. Check it out:

“The red supergiant star Betelgeuse, in the constellation of Orion, has been undergoing unprecedented dimming,” the European Southern Observatory writes. “This stunning image of the star’s surface, taken with the SPHERE instrument on ESO’s Very Large Telescope late last year, is among the first observations to come out of an observing campaign aimed at understanding why the star is becoming fainter. When compared with the image taken in January 2019, it shows how much the star has faded and how its apparent shape has changed.”

Because only part of the star is changing in brightness, its shape appears to be altered, giving it an oblong appearance as opposed to a more uniform circular shape. So, what’s the deal?

As Plait points out, nobody can say for certain, at least not yet, but one possibility is that the supergiant star’s surface has been stained with a particularly large sunspot. Our own star gets sunspots from time to time, but they’re usually quite small. On a star like Betelgeuse, things are a lot different, and the turbulent magnetic forces at work may have produced a particularly massive sunspot that is actually making the entire star appear less bright.

The odds that Betelgeuse is preparing to blow its top still appear very slim, and it’s highly unlikely we’re about to witness the supergiant go full supernova anytime soon. Still, until anyone can conclusively explain what’s going on with the star, scientists will be keeping a particularly close eye on it.

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