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Everything dies sooner or later, even stars. The death of a red supergiant like Betelgeuse is “one of the most dramatic and violent events in space.” For the first time ever, “astronomers had an unprecedented front-row seat to the explosive end of a stellar giant.” It wasn’t Betelgeuse that blew up. Not this time. That familiar red supergiant at the shoulder of Orion “has captured interest due to its irregular dimming” and is predicted to “go supernova,” but it hasn’t happened yet.
Death of a supergiant
Astronomers with ground based telescopes like the one at Keck Observatory in Hawaii were lucky enough to witness what was happening live, as the cameras captured “the first real-time look at the death throes of a red supergiant star.”
They aren’t very bright but they’re massive. That means when they run out of energy and collapse, they make nifty things like black holes and neutron stars.
If you look closely at the NGC 5731 galaxy, which is somewhere around 120 million light-years away from Earth, you can still see the dust settling. The star which had it’s name changed to SN 2020tlf during the supernova event “was 10 times more massive than the sun before it exploded.”
Stars like that “go out in a blaze of glory,” but before they do, “some stars experience violent eruptions or release glowing hot layers of gas.” Those are clues that a big explosive death is about to happen.
Until they got a good look at one with sophisticated instruments, astronomers “believed that red supergiants were relatively quiet before exploding into a supernova or collapsing into a dense neutron star.” They were astonished to watch in real time as the star began to “self-destruct in dramatic fashion before collapsing in a type II supernova.”
They note this “star death is the rapid collapse and violent explosion of a massive star after it has burned through the hydrogen, helium and other elements in its core.”
After the blast
Once a collapsing star blasts off all the outer layers, the only thing left is the iron. The problem is that “iron can’t fuse so the star will run out of energy.” When that happens, death of the star is the only possible outcome.
“When that happens, the iron collapses and causes the supernova.” When Wynn Jacobson-Galán put the paper bearing his name as lead author into the Astrophysical Journal, he declared it “a breakthrough in our understanding of what massive stars do moments before they die.”
The team was thrilled to be able to announce that direct “detection of pre-supernova activity in a red supergiant star has never been observed before in an ordinary type II supernova.”
“For the first time, we watched a red supergiant star explode.” The “final moments of stellar death” were spectacular. They wouldn’t have been watching if it wasn’t for some clues they picked up earlier.
The first warning astronomers got of the impending star death was “unusual activity 130 days before it went supernova.” In the summer of 2020, “bright radiation was detected” by the University of Hawaii Institute for Astronomy Pan-STARRS telescope on Maui’s Haleakalā. They caught the supernova “using the W.M. Keck Observatory’s Low Resolution Imaging Spectrometer on Maunakea, Hawaii”
The images reveal “there was material around the star when it exploded — the bright gas that the star violently kicked away from itself over the summer.” One team researcher, Raffaella Margutti, observes “It’s like watching a ticking time bomb. We’ve never confirmed such violent activity in a dying red supergiant star where we see it produce such a luminous emission, then collapse and combust, until now.”
