Betelgeuse: Giant star is slowly becoming brighter again - Supernova probably canceled

The star Betelgeuse shines as weakly as never before. Will it soon end up as a supernova, i.e. will it explode? A simulation shows what that means.

• The star Betelgeuse in the constellation Orion could soon explode as a supernova
• Researchers see possible signs of this: Betelgeuse loses massive brightness
• Now Betelgeuse is particularly closely observed by astronomers - and the loss of brightness slows down

Update from February 25, 2020: The star Betelgeuse is apparently getting brighter again. That's what astronomers Edward Guinan, Richard Wasatonic, Thomas Calderwood and Donald Carona write in the "Asteronomers Telegram". Photometric recordings from the past two weeks showed that the rapid loss of brightness of Betelgeuse stopped. That is about 424 days after the last observed light minimum in mid-December 2018 and thus fits exactly with a 420 to 430 day long light cycle of the star, according to the scientists.

"Betelgeuse has definitely stopped darkening and has started to get brighter again," write the astronomers. "Observations of all kinds are needed to understand the background of this unprecedented dimming," the scientists continued. With the help of observations one also wants to find out "what this surprising star will do next".

Simulation shows what happens when Betelgeuse explodes as a supernova

Update from February 18, 2020: What does it actually look like when the star Betelgeuse explodes as a supernova at some point? Astronomer Andy Howell (University of California) and two of his students, Jared Goldberg and Evan Bauer, answered this question and performed simulations to show how bright the supernova will be. The result is impressive:

If Betelgeuse explodes at some point - in the near future or only in 100,000 years - a particularly rare sky spectacle will emerge. "All of the brightness would be concentrated in one point," Howell told Discover Magazine. "Everyone in the world would be curious because it would be obvious," Howell emphasizes.

What happens when Betelgeuse becomes a supernova?

The researchers' insights at a glance:

• Betelgeuse would shine very brightly in the sky as a supernova - there would even be shadows at night
• The supernova would shine as bright as the crescent for about three months and nine times weaker than the full moon
• The glowing supernova would also be visible in the daytime sky for about a year
• The glowing supernova would be seen with the naked eye in the night sky for several years
• When the supernova finally fades, the constellation Orion lacks the left shoulder

If the star Betelgeuse explodes at any time, it poses no threat to the earth, because the star is, according to new estimates, about 724 light years from Earth. Nevertheless, there could be unexpected effects on the earth: Many animals use the moon for orientation and are confused by artificial light sources. A "second moon" should disturb them even more, explains astronomer Howell.

And people - ironically, of all people, astronomers - are likely to be affected by the bright light of the supernova: "Astronomical observations are already very difficult when the moon is shining brightly," Howell said. And if Betelgeuse explodes one day, there is no "real" darkness for a long time. Betelgeuse itself would then also be difficult to observe: the brightness of the star would be a problem for many instruments.

Star Betelgeuse has lost more than a third of its brightness

Update from February 14, 2020: What happens to the red giant Betelgeuse in the constellation Orion ? The once strikingly bright star has been darkening since autumn 2019 - and researchers are wondering why. Since December 2019, a team led by astronomer Miguel Montargès from Belgium has been observing the Betelgeuse star with the "Very Large Telescope" of the European Southern Observatory ESO and trying to find out why the star is losing its brightness.

"We are working on two scenarios: that the surface cools down due to extraordinary stellar activity or that dust is thrown in our direction," said Montargès in a statement from ESO. "Our understanding of giant red stars is incomplete, so a surprise can happen at any time," emphasizes Montargès.

The star Betelgeuse, found in the constellation Orion, recorded by the "Very Large Telescope" of the ESO. The image comparison clearly shows that Betelgeuse is losing its brightness. Left: January 2019, right: December 2019.

© ESO / M. Montargès et al.

Because the team observed Betelgeuse in January 2019, before and after pictures were taken that illustrate the loss of brightness of the star. Betelgeuse has currently lost about 36 percent of its brightness, reports the ESO.

Weaking star Betelgeuse approaches the minimum of a light cycle

Update February 4, 2020: Researchers Edward F. Guinan and Richard J. Wasatonic sign up with further information about the ailing star Betelgeuse to speak. According to the researchers, Betelgeuse is now about a whole magnitude darker than in September 2019. The magnitude indicates the apparent brightness of a celestial body, as an observer perceives it on Earth. The lower the magnitude, the brighter the object. Some examples:

• Full moon: -12.73 mag
• Planet Venus 4.67 mag
• Star Sirius -1.46 mag
• Polarstern 1.97 mag

The researchers recently found values ​​of around 1.6 mag for Betelgeuse, normally the variable star fluctuates between 0 and 1.3 mag.

Some experts assume that the star Betelgeuse shines weaker as it approaches the minimum of a light cycle. Its minimum is reached around February 21 (+/- seven days) - then Betelgeuse should become brighter again. Observations from the past few weeks also seem to show that the weakening of Betelgeuse is slowing. "Observations in the next few months will be important," write the researchers in the "Astronomers Telegram".

Betelgeuse in the constellation Orion: what is going on with the giant star?

Update of January 23, 2020: The researchers, who first point to the rapid loss of brightness of the star Betelgeuse in the constellation Orion , have spoken with new figures: Since September 2019, the star has lost about 25 percent of its brightness, the researchers write in " Astronomers Telegram ”. Like other experts before them, Edward F. Guinan and Richard J. Wasatonic emphasize that the drop in brightness at Betelgeuse may be related to the star's approximately 420-day light cycle.

Then the minimum is expected for late January or early February 2020, the researchers said. "If Betelgeuse gets weaker afterwards, you should think about other options," the scientists continue. "The unusual behavior of Betelgeuse should be closely monitored." However, they also indicate that the diminution of Betelgeuse may be slowing down at the moment.

Is the star Betelgeuse standing in front of a supernova in the constellation Orion?

However, what is known today gives rise to the assumption that Betelgeuse is facing a supernova : the star has lost massive brightness since October 2019. Measurements from mid-December 2019 show that Betelgeuse never shone as dimly as it does now, researchers recently reported.

Betelgeuse is actually one of the six to seven brightest stars in the night sky . However, the researchers are currently only locating the star at position 21 - the loss of brightness is so drastic. And the temperature of the star has also changed, according to the researchers: They measured 150 degrees Kelvin less than during the maximum brightness.

Sun, moon and stars - this will happen in 2020 on the (night) sky *

Supernova in the constellation Orion: What are the consequences for Earth?

Something else about Betelgeuse is special: If the star explodes, it is the first supernova in our galaxy since 1604. At that time Johannes Kepler observed a supernova in the constellation Snake Bearer (Ophiuchus). For astronomers, a supernova that is only 700 light years away would be like winning the lottery: You could virtually observe a star explosion up close, instead of having to look into the vastness of the universe *.

At the same time, Betelgeuse is far enough away from Earth that an explosion poses no threat to our planet. Researchers are currently assuming that a supernova at a distance of 50 light years from the earth could trigger a mass extinction. "The critical distance of a supernova, which could have a negative impact on our life on Earth, is about 200 light years," explains Hans-Thomas Janka from the Max Planck Institute for Astrophysics in Garching in an interview with weltderphysik.de.

Betelgeuse is about 700 light years from Earth - and will probably be under permanent observation by astronomers in the future. Because nobody wants to miss a supernova in the direct cosmic neighborhood.

Star Betelgeuse is the focus of astronomers

Update from January 16, 2020: What's going on with the Giant Star Betelgeuse? The star, which is currently losing massive brightness and suspects astronomers of blessing time with a massive supernova explosion, is back in the focus of astronomers. Because recently the gravitational wave detectors Ligo and Virgo recorded an unexpected "outbreak" of gravitational waves.

More specifically, on January 14, the detectors recorded a special type of gravitational wave that had never been recorded before. Scientists suspect that they may have something to do with phenomena such as supernovae or gamma-ray bursts. The recorded outbreak was given the complicated name S200114f, astronomers chased it back and found that it came roughly from the region near the star Betelgeuse.

Betelgeuse is not in the localizatiion region, but it is right between two of them, as you can see at https://t.co/E5cyQ4NMtY. pic.twitter.com/89LtVoWniK

Did Betelgeuse explode? Gravitational wave detectors measure outburst

Was it a sign that Betelgeuse has now exploded? Rather not. The star Betelgeuse can still be seen in the sky, as several astronomers checked and wrote on Twitter. In addition, Betelgeuse is not in the region in which the outbreak was measured, Andy Howell emphasizes on Twitter.

What is behind the eruption that the gravitational wave detectors recorded has so far been unclear. Astronomers observe the region in which the eruption was measured - but it could also have been a false alarm.

Star Betelgeuse in the constellation Orion is actually striking and well-known

First announcement from January 1, 2020: If you are currently looking at the starry sky in the evening or at night, you will almost certainly see it: the constellation Orion . It has the shape of an egg timer, but is said to represent the “hunter” Orion: three stars stand close together and form a “belt”. Two stars above and two stars below also belong to the constellation. Below the three belt stars you can often see the Orion Nebula with the naked eye.

At the moment, however, one star in the constellation Orion is the center of attention: the shoulder star of Orion in the top left, called Betelgeuse (Alpha Orionis) . It is a so-called red supergiant, which has a rather short lifespan compared to other star classes. A red supergiant usually ends its star life with a violent explosion, a supernova. And that's exactly what experts suspect could happen to Betelgeuse soon.

The Betelgeuse star in the Orion constellation is 700 light-years from Earth

Or, it may have happened many years ago and the light of the supernova is only now reaching Earth. Betelgeuse is about 700 light years away from Earth - this means that the light of the star takes 700 years to reach Earth.

Conversely, this means that the light from Betelgeuse , which you can currently see in the night sky, was emitted 700 years ago. Whether Betelgeuse still looks like what you can currently see in the night sky or whether the star has already exploded - in the distant future astronomers will know, at the moment one can only guess.

Betelgeuse in Orion is a variable star - but it has never been so faint

Betelgeuse is a variable star that changes its brightness regularly. It follows two light cycles: one is about 425 days long, the other takes about 5.9 years. That Betelgeuse lost so much brightness could be due to the fact that the minimum of both light cycles is approaching.

However, it could also mean that the red supergiant Betelgeuse is nearing its end: when the star runs out of fuel, it begins to collapse - in the process it loses its brightness and then breaks out into a spectacular explosion .

Supernova from Stern Beteigeuze would be a spectacle - even in daylight

This star death * would not be overlooked from Earth either: Experts expect the supernova of a red supergiant to increase its luminosity on average by 16,000 times. For Betelgeuse, that would mean that the supernova would be as bright as the crescent, possibly even as the full moon. In any case, it is clear that it cannot be overlooked and that it would also be visible during the day.

A look into space: Betelgeuse Imagined https://t.co/0j89GgSv20 #Astronomie pic.twitter.com/q9FsLZFswk

Researchers estimate that Betelgeuse ages around 10 million years. Some assume that the star will become a supernova within the next thousand years - a very short period of time in astronomical terms. However, others suspect that it will take much longer.

Betelgeuse is huge: the star is a thousand times the diameter of our sun and about ten thousand times as luminous as the sun. If Betelgeuse took the position of our sun, the surface of the star would reach as far as Jupiter.

By Tanja Banner

* fr.de is part of the nationwide Ippen-Digital central editorial office.

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