Supergiant star explosion seen live by astronomers in unprecedented breakthrough

Scientists have watched live as a red supergiant star came to its dramatic end for the first ever time.

The research marks a major moment for our understanding of the death throes of stars – those moments before they detonate in spectacular, violent eruptions.

It also suggests that our understanding of what happens before red supergiants explode is wrong. Previously, they looked as if they were relatively calm before bursting into their dramatic death – but in the latest observations, scientists saw bright radiation coming from the star that seemed to indicate something more significant was happening inside.

“This is a breakthrough in our understanding of what massive stars do moments before they die,” said Wynn Jacobson-Galán, the study’s lead author.

“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 research, ‘Final Moments. I. Precursor Emission, Envelope Inflation, and Enhanced Mass Loss Preceding the Luminous Type II Supernova 2020tlf’, is published today in the Astrophysical Journal.

Researchers first spotted the doomed star in summer 2020, when vast amounts of light were spotted coming out of it by the University of Hawaiʻi Institute for Astronomy Pan-STARRS on Haleakalā. They were then able to watch it – with that telescope and the nearby WM Keck Observatory on Maunakea – in the days that followed, until it exploded in a bright supernova a few months later.

“It’s like watching a ticking time bomb,” said Raffaella Margutti, an adjunct associate professor at CIERA and the paper’s senior author. “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.”

Astronomers now hope they can use the research to look through the universe for more stars that are throwing out that luminous, ominous radiation and see whether it signals the imminent death of that star.

“I am most excited by all of the new ‘unknowns’ that have been unlocked by this discovery,” said Jacobson-Galán.

“Detecting more events like SN 2020tlf will dramatically impact how we define the final months of stellar evolution, uniting observers and theorists in the quest to solve the mystery on how massive stars spend the final moments of their lives.”