Astronomers find more clues behind the giant star’s “great dimming”


Between November 2019 and March 2020, a massive star dimmed in an unprecedented way, confusing astronomers. Some people hope this indicates that the star is dying and will cause a spectacular explosion, illuminating the sky like a full moon.

That never happened, and the star-Betelgeuse-returned to its normal brightness. Now in a new study, astronomers believe they may have figured out why this happened.

Betelgeuse is a red supergiant star, a massive star discovered in the constellation Orion. It is 700 light-years away from the Earth. It is believed to be approximately 1,400 times the sun and 14,000 times brighter than the sun.

This star is also a semi-regular variable, which means that its brightness will increase and decrease periodically. Eventually, the red supergiant ran out of fuel and died in a spectacular supernova explosion. Some people watching the dimming wonder if this is a sign that it is about to die.

But in 2020, it is clear that its dimming is not part of any of its regular cycles, but what caused it is still a mystery.

Now a New paper published in the journal Nature It was shown on Wednesday that the dimming was caused by dust that obscured some of the stars.

These images were taken with the SPHERE instrument on the European Southern Observatory’s Very Large Telescope and show the surface of the red supergiant star Betelgeuse during the unprecedented dimming period in late 2019 and early 2020. (ESO / M. Montargès et al.)

However, how the dust gets there is actually completely related to something else: the cooling period of the star.

The authors of the study believe that gas is released by stars, which is considered to be a frequent occurrence. But then part of Betelgeuse cooled, causing the gas to turn into dust, which then obscured part of the star.

Miguel Montarges is the lead author of the study and a postdoctoral researcher at LESIA at the University of Paris. He has been studying Betelgeuse throughout his career. Just 12 months before the “Great Dimming Event”, he collected data from giant stars in the Very Large Telescope (VLT) of the European Southern Observatory (ESO) in 2019.

“I remember hoping that something will happen this year because I am observing Betelgeuse at VLT,” he said. “Every year, I make a wish for a big comet or supernova. I say,’I want something to happen.’ And something happens.”

All eyes are on Betelgeuse

When astronomers began to observe dimming, Montargis was skeptical.

“In November, when we first received an email saying,’Oh, it’s a little weaker than usual,’ my reaction was that it was too early to say that something important was happening,” he said.

But soon, no one ignored it. So Montargis thought he would take some observations and prove that nothing abnormal happened. He believes this is because the two cycles of Betelgeuse’s normal dimming happened to combine to form a deeper dimming.

He was wrong. The star eventually dimmed by about 25%.

Astronomers around the world have observed this event using instruments that observe it in a variety of different ways.

Watch | Betelgeuse dimmed:

“We have small telescopes, large telescopes, space telescopes; we have radio telescopes [spectrum], In the infrared, in the ultraviolet,” said Emily Levesque, a professor in the Department of Astronomy at the University of Washington, who published an accompanying article natural Regarding the survey results.

“We are studying polarized light, we are studying spectroscopy. I like it to show how many different tools and astronomy we can use from’hey, this is weird’ to now we can explain what is happening.”

‘Snapshot of this star’

Stella Kafka, director of the American Association of Variable Star Observers who was not involved in the study, said that one of the surprising things is that there are so many instruments to collect data on Betelgeuse.

“We are looking at a snapshot of this star. But at the same time, this snapshot clarifies something for us at that particular stage of evolution,” she said. “So in principle, the advantage of this special manuscript is that they are introducing new data and new technologies.”

Several astronomers have published research reports, some of which indicate dimming Because of cooling; Others think this is a A dust cloud that hides some stars. New research shows that this is a combination of the two.

In this research, astronomers proposed four scenarios that could explain the dimming of Betelgeuse:

  1. The “potentially local” temperature drop makes it darker.
  2. A newly formed cloud of dust blocked it.
  3. An occultation of dust that happens to pass in front of it (something passes in front of other things).
  4. Change in angular diameter (the diameter of Betelgeuse from the earth)

The author ruled out the third case, because passing dust clouds would pass through different parts of the star, and this was not observed. After reviewing the data collected from the two instruments on the VLT, Scenario 4 was also ruled out.

This picture shows the position of the red supergiant Betelgeuse in Orion. Betelgeuse is the right shoulder of Orion and can be easily seen without a telescope, as shown in the picture. (ESO / N. Risinger (skysurvey.org))

Instead, they believe that some time before the big dimming, the star released a bubble. Initially, the area around the star was too hot to form dust. However, during a period of the normal cycle, the star has cooled enough to allow this to happen.

Betelgeuse is not the only red supergiant, although it may be the most well-known and most studied, and it is not known whether this type of event is a typical feature of these giants. Antares is another famous red supergiant star located in the summer constellation (Northern Hemisphere) Scorpio.

A kind Antares research A study led by Emly Cannon, a co-author of this recent study and a PhD student in astrophysics at the University of Leuven in Belgium, found that although it is not in our line of sight, there is a cluster of dust around the star.

Cannon said: “So this shows to some extent that these dust clumps…may not be that special.” “Maybe this is all the red supergiants we have seen. It’s just that this one happened to be sprayed around us, And other times it just ejects from the part of the star we can’t see.”

Although Betelgeuse will explode one day, this incident is unlikely to indicate that it is about to die. It may take tens of thousands or even hundreds of thousands of years.

Montarges will continue to follow Betelgeuse to help better understand stellar evolution and our place in it.

“It is surprising that we are only a small part of the universe, trying to understand the universe.”



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