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Scientists might have figured out why Betelgeuse keeps dimming

Published Aug 14th, 2020 10:10PM EDT
betelgeuse dimming
Image: NASA, ESA, and E. Wheatley (STScI)

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  • Astronomers using observations from the Hubble Space Telescope have come up with a new theory as to why the star Betelgeuse is dimming.
  • The researchers believe they see evidence of a massive cloud of dust and gas that was expelled by the star, blocking some of its light toward Earth.
  • Some scientists theorized that Betelgeuse was about to explode, but that doesn’t seem to be the case.

Betelgeuse, a massive nearby star that sits a mere 725 light-years away, has been acting very odd lately. Astronomers have noticed that it’s been dimming at regular intervals and haven’t been able to conclusively explain the cause. Some theories — such as the star approaching its supernova stage — don’t appear to line up well with what we know about the Betelgeuse.

Now, in a new study published in The Astrophysical Journal, scientists using observations by the Hubble Space Telescope think they may have uncovered the reason for the star’s odd behavior. And no, it’s not about to explode.

Over decades of study, researchers had become accustomed to Betelgeuse going through a cycle of dimming every 400 days or so. That all changed late last year when the star began dimming outside of its standard cycle. This led to many questions, including whether or not the star might be about to explode as a supernova.

Using Hubble observations going back several months, the researchers now say they have a much better idea of what is causing the unexpected changes in brightness. As it turns out, the star itself might not be dimming at all, it’s just that from our perspective the star’s light has become partially blocked.

As the researchers explain in the new research paper, the star appears to have ejected a whole bunch of plasma, forming a cloud that, when cooled, formed dust and gas that is now blocking the star’s brightness from our perspective. The cloud of material is speeding along at an incredible 200,000 miles per hour, the scientists say.

“With Hubble, we see the material as it left the star’s visible surface and moved out through the atmosphere, before the dust formed that caused the star to appear to dim,” Andrea Dupree, lead author of the study, said in a statement. “Only Hubble gives us this evidence of what led up to the dimming.”

It’s still not immediately clear why the star belched out so much material at once, but it’s not entirely uncommon for stars to gradually lose their material to space.

“All stars are losing material to the interstellar medium, and we don’t know how this material is lost,” Dupree explains. “We know that other hotter luminous stars lose material and it quickly turns to dust making the star appear much fainter. But in over a century-and-a-half, this has not happened to Betelgeuse. It’s very unique.”

Perhaps it was just making up for lost time.

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