Scientists see in real time the giant star explosion in its final minutes

The death of a star is one of the most dramatic and violent events in space — and astronomers watched from their cabins the explosive end of a stellar giant, something unprecedented.

Ground-based telescopes provided the first real-time view of the suffering death of a red supergiant star. While not the brightest and most massive stars, they are the largest in terms of volume.

A popular red supergiant star is Betelgeuse, which has attracted interest due to its irregular dimming. Even though Betelgeuse has already been predicted to become a supernova, it’s still out there.

However, the central star of this new survey, located in galaxy NGC 5731 120 million light years from Earth, was 10 times more massive than the sun before its explosion.

Before they come out in all their glory, some stars face violent eruptions or release layers of hot, luminous gases. Until astronomers witnessed this event, they believed that red supergiants were relatively calm before they exploded and became supernovae or a collapsed neutron star.

However, scientists changed their minds as they watched the star dramatically destroy itself before becoming a type II supernova. The death of this star is the result of the rapid collapse and violent explosion of a huge star after burning hydrogen, helium and other elements in its core.

All that’s left is your iron, but iron can’t melt, so the star runs out of energy. When this happens, the iron collapses and causes a supernova. A study detailing these findings was published last Thursday in The Astrophysical Journal.

“This is a breakthrough in our understanding of what happens in massive stars moments before they die,” said lead author of the study, Wynn Jacobson-Galán, National Science Foundation Graduate Research Fellow at the University of California, Berkeley, in a statement.

“Direct detection of pre-supernova activity in a red supergiant star has never been observed before in a common type II supernova. For the first time, we watched a red supergiant star explode.”

Final moments of a star death

Astronomers were initially alerted to unusual stellar activity 130 days before it became a supernova. Bright radiation was detected in the summer of 2020 by the Pan-STARRS telescope at the Institute of Astronomy at the University of Hawaii in Haleakalā, Maui region.

Then, in the fall of that year, researchers witnessed the supernova at the same location.

They observed using the WM Keck Observatory’s low-resolution imaging spectrometer in Mauna Kea, Hawaii, and named the supernova ‘2020tlf’. His notes revealed that there was material around the star when it exploded—the bright gas that the star spewed out violently during the summer.

“It’s like watching a time bomb,” said the study’s fellow author, Raffaella Margutt, associate professor of astronomy and astrophysics at the University of California, in a statement. “We’ve never seen such violent activity on a dying red supergiant star where we see it produce such a light emission and then collapse and combust, that’s until now.”

Some of these massive stars likely undergo consequent internal changes that cause a tumultuous release of gas before they die, the finding revealed.

The work was conducted while Jacobson-Galán and Margutti were still at Northwestern University. They had remote access to the telescopes at the Keck Observatory in Hawaii, which were “an important instrument in providing direct evidence of the explosion of a massive star transitioning to a supernova,” says Margutti.

“I’m most excited about all the new ‘unknowns’ that have been revealed by this discovery,” said Jacobson-Galán. “Detecting more events like SN 2020tlf will dramatically impact how we define the final months of stellar evolution, bringing together observers and theorists in the saga of solving the mysteries of how giant stars spend the final moments of their lives.”