Scientists observe the explosion of a red supergiant star for the first time

The red supergiant became, after months, a supernova  and astronomers witnessed the event.

For the first time, astronomers have seen the end of a red supergiant in real time , observing the rapid destruction of the massive star before collapsing into a  Type II supernova .

Using two telescopes in Hawaii, the University of Hawaii’s Pan-STARRS Astronomy Institute and the WM Keck Observatory, a team of researchers conducting the YSE (Young Supernova Experiment) study observed the red supergiant during its last 130 days before of its deadly detonation.

“This is a major advance in our understanding of what massive stars do just before they die,” says Wynn Jacobson-Galán, a UC Berkeley NSF graduate researcher and lead author of the study. “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 star explode !”

The discovery appears in The Astrophysical Journal .

I was doomed

Pan-STARRS first detected the massive doomed star in the summer of 2020 through the large amount of light radiated by the red supergiant . A few months later, in the fall of 2020, a supernova lit up the sky.

The team quickly captured the powerful flash and obtained the first spectrum of the energy blast, called a supernova 2020tlf, or SN 2020tlf, using the Keck Observatory’s Low Resolution Imaging Spectrometer (LRIS). The data showed direct evidence of dense circumstellar material surrounding the star at the time of the explosion, probably the same gas that Pan-STARRS had seen violently expelled from the supergiant star in early summer.

“Keck was instrumental in providing direct evidence of a massive star transitioning into a supernova explosion, ” says lead author Raffaella Margutti, associate professor of astronomy at UC Berkeley. “It’s like seeing a time bomb. We have never confirmed such violent activity in a dying red supergiant star where we see it produce such a luminous emission, then collapse and burn, until now.”

The team continued to monitor SN 2020tlf after the explosion; Based on data obtained from the Keck Observatory Multi-Object and Deep Imaging Spectrograph (DEIMOS) and the Echellette Near Infrared Spectrograph (NIRES), they determined the red supergiant progenitor star of SN 2020tlf, located in the galaxy NGC 5731 at about 120 million Light years distant as seen from Earth, it was 10 times more massive than the Sun.

The discovery challenges previous ideas of how red supergiant stars evolve just before exploding. Prior to this, all of the red supergiants observed before exploding were relatively dormant: they showed no evidence of violent eruptions or light emission, as observed prior to SN 2020tlf.

However, this new detection of bright radiation from a red supergiant in the last year before exploding suggests that at least some of these stars must undergo significant changes in their internal structure that then result in the tumultuous ejection of gas moments before collapsing. .