Astronomers see real-time destruction of red supergiant star

When very large stars run out of fuel and reach the end of their life, they can explode in massive and dramatic events called supernovas. These explosions project huge amounts of light and energy, but we still don’t know much about how this process occurs. Today, astronomers first observed a red supergiant star turn into a supernova, seeing the last moments of the massive star’s life.

“This is a breakthrough in our understanding of what massive stars do moments before they die,” said Wynn Jacobson-Galán, lead author of the study, said in a declaration. “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 saw a red supergiant explode!

Artist's impression of a red supergiant star in the last year of its life emitting a tumultuous cloud of gas.
Artist’s impression of a red supergiant star in the last year of its life emitting a tumultuous cloud of gas. This suggests that at least some of these stars undergo significant internal changes before becoming a supernova. WM Keck / Adam Makarenko Observatory

The team observed the SN 2020tlf supernova using two telescopes at Hawai’i, Pan-STARRS and the WM Keck Observatory. They were able to spot the red supergiant before the supernova appeared because it gave off large amounts of light and ejected large amounts of gas. They observed the star for 120 days before it became a supernova in the fall of 2020, and they saw a dense cloud of gas surrounding the star when it exploded.

“Keck helped provide direct evidence for the transition from a massive star to a supernova explosion,” said lead author Raffaella Margutti, associate professor of astronomy at UC Berkeley. “It’s like looking at a time bomb. We have never confirmed such violent activity in a dying red supergiant star where we see it producing such a bright emission, then collapsing and burning, until now.

The star that exploded was particularly large, 10 times the mass of the sun, and was located 120 million light years away in the galaxy NGC 5731. It is of particular interest to researchers because it was so active before it exploded, whereas it had been observed before. the red supergiants were relatively calm before they became supernovas.

“I am very excited by all of the ‘unknown’ news that has been unlocked by this discovery,” said Jacobson-Galán. “Detecting more events like SN 2020tlf will have a huge impact on how we define the final months of stellar evolution, uniting observers and theorists in the quest to solve the mystery of how massive stars pass the last moments of their life. “

The results are published in The Journal of Astrophysics.

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