Mystery solved: Betelgeuse, the dimming star that drew international attention, isn’t exploding – it was just dusty

betelgeuse star orange light dimming in space
These images, taken by the Very Large Telescope, show the surface of the red supergiant star Betelgeuse during its dimming from January 2019 (far left) to March 2020 (far right).

Scientists have solved one of the most sensational cosmic mysteries in recent memory – and they can chalk the whole thing up to dust.

The red super-giant star Betelgeuse enraptured the world early last year after scientists noticed that it was dimming. That was taken as a potential sign that the star was beginning to die, collapsing and losing energy – a process that would eventually end in a giant supernova explosion. Betelgeuse, then, could have been the first supernova observed in our galaxy since the 17th century. The effect likely would have been visible to the naked eye, shining bright in the sky for months.

But it turns out the star isn’t blowing up after all. According to a study published in the journal Nature on Wednesday, it just appeared to be dimming because a veil of dust was shrouding the star.

“For once, we were seeing the appearance of a star changing in real time on a scale of weeks,” astrophysicist Miguel Montargès, the lead author of the new study, said in a press release. “We have directly witnessed the formation of so-called stardust.”

Betelgeuse dust plumes
Clouds of dust can be seen in this picture of Betelgeuse -the center of the bright star that would normally obscure the dust is blocked out. This image was taken by the Very Large Telescope in December 2019.

To figure out what was happening to Betelgeuse, Montargès and his team of researchers monitored the star’s dimming with telescopes on Earth, which allowed them to see the details on its surface. They kept at it through April 2020, as the star returned to its original brightness.

In the end, they concluded that the star had simply belched out a large bubble of gas. Shortly afterwards, a patch of its surface cooled down enough to condense some of that gas into dust. The cloud of dust lingered for months, blocking Betelgeuse’s light and making it look darker and darker from Earth’s vantage point.

Even though Betelgeuse isn’t going supernova, its dimming still offered an important display of a critical cosmic process.

“The dust expelled from cool evolved stars, such as the ejection we’ve just witnessed, could go on to become the building blocks of terrestrial planets and life,” Emily Cannon, a co-author of the study, said in the release.

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The biggest volcano eruptions in recorded history

  • The Volcanic Explosivity Index (VEI) ranks volcano eruptions by size and power.
  • The scale goes from VEI-0 to VEI-8 and measures ash, lava, and rock ejected.
  • VEI-1 is a gentle eruption that can happen frequently. Italy’s Mt. Stromboli has been erupting almost continuously for 2,000 years.
  • VEI-6s are colossal eruptions every 100 years. The 1883 explosion of Krakatoa was the most famous of these.
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Following is a transcript of the video.

Earth has had a dramatic history, filled with its share of angry outbursts. Here’s how the largest volcanic eruptions measure up.

The Volcanic Explosivity Index (VEI) ranks eruptions by size and power. The scale goes from VEI-0 to VEI-8. It measures ash, lava, and rock ejected.

VEI-0 are usually a steady trickle of lava instead of an explosion. An example is the Hawaiian volcano of Kīlauea.

Next is VEI-1, a gentle eruption that can happen frequently. Italy’s Mt. Stromboli has been erupting almost continuously for 2,000 years.

VEI-2s consist of several mild explosions a month. Indonesia’s Mount Sinabung has been erupting since 2013.

VEI-3 are catastrophic eruptions that happen every few months. Lassen Peak in Northern California had a VEI-3 in 1915.

VEI-4s happen about every other year. In 2010, Iceland’s Eyjafjallajökull grounded thousands of flights.

At VEI-5 things start getting more dramatic. Both Mt. Vesuvius (79 AD) and Mt. St. Helens (1980) were VEI-5s.

VEI-6s are colossal eruptions every 100 years. The 1883 explosion of Krakatoa was the most famous of these.

VEI-7 eruptions occur every 1,000 years. The most recent was Indonesia’s Mt. Tambora in 1815.

VEI-8 is a devastating explosive eruption every 50,000 years. The Yellowstone Caldera would reach this level if it were to erupt.

Let’s all just keep our cool.

EDITOR’S NOTE: This video was originally published on November 1, 2017.

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