Betelgeuse Is Haunted by a Hotspot That Should Be Long Gone

Six hundred light-years away, a star 800 times as wide as the sun is bubbling like a pot left on too high. Anything boiling has hotspots, and they never stay put. One of Betelgeuse's has sat in the same place for at least seven years.

The Atacama Large Millimeter/submillimeter Array, or ALMA, imaged Betelgeuse in 2023 in unusually fine detail. The star carries about 20 times the sun's mass, and its surface turns out to be rippled and lopsided, with its apparent radius varying by up to about 6 percent. The gas there averages around 3,680 degrees Fahrenheit (2,030 degrees Celsius). At least two regions run hotter, and the brightest is about 1,440 degrees Fahrenheit (800 degrees Celsius) above its surroundings.

Astronomers think the hotspots come from convection on an enormous scale. Hot gas wells up from deep inside the star and can send shocks through the outer atmosphere when it arrives.

That's the textbook answer. The textbook doesn't cover what turned up when the team checked ALMA's 2015 images. The big northeastern hotspot was already there, in nearly the same position and about as bright. Current models say a feature like that should be long gone. Its orientation is its own puzzle, because Betelgeuse appears to have a close companion star, and nothing in the new images ties the two together. Not yet.

Betelgeuse made news a few years ago when a sudden dimming had some astronomers wondering whether it was about to blow. It still hasn't.

It will one day. Somewhere in its northeast, one patch of gas does not seem to be in any hurry.

Read the full story at Space.com, August 25, 2026

Hot Take: Astronomers keep saying this star's name, and every time they do, something uninvited turns up. That sounds like an excellent reason to say it again.