An agony of self-destruction, death, and supernova collapse . This has been the dramatic event that, for the first time, a team of astronomers from Northwestern University and the University of California, Berkeley (USA) have seen in real time.
Something that had been looking for a long time: contemplate the last days of a giant star before exploding.
Red supergiant stars with masses more than eight times that of the Sun, have a very cold surface below 3800 ºC and enormous radii (between 200 and 800 times greater than that of the Sun). They become Type II (or Ib/Ic) supernovae, leaving behind a neutron star or black hole. Although we haven’t seen such an event in the Milky Way in the last 400 years, we currently see hundreds of outbursts like this in other galaxies each year.
This discovery challenges previous ideas about how red supergiant stars evolve just before they explode. Previous observations showed that red supergiants were relatively inactive before their deaths, without violent eruptions or luminous emissions. The new observations, however, show just the opposite.
Scientists detected bright radiation from a red supergiant in the last year before it exploded, suggesting that at least some of these stars must undergo significant changes in their internal structure, which then lead to the tumultuous expulsion of gas moments before collapsing into supernova form.
“This is a great advance in our understanding of what massive stars do moments before they die,” says Wynn Jacobson-Galán, lead author of the study published in The Astrophysical Journal . “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 team captured the violent event in real time using the Keck Observatory’s Low Resolution Imaging Spectrometer in Maunakea, Hawaii which was also used to image the event in real time. They were able to capture the powerful and energetic explosion, which the researchers named supernova 2020tlf (SN 2020tlf).
“We have never confirmed such violent activity in a dying red supergiant star where we see it produce such luminous emission, then collapse and burn, until now,” says study lead author Raffaella Margutti.
Astronomers hope to detect more events like SN 2020tlf , in a bid to better understand the evolution and eventual demise of stars. In 2019, the red supergiant star Betelgeuse, located within the Milky Way, dimmed to its lowest brightness level in years, leading some astronomers to believe it might be on the verge of going supernova. However, unlike the star in NGC 5731, Betelgeuse remains intact.
“The detection of more events like SN 2020tlf will have a dramatic 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 spend the final moments of their lives.” lives “, exposes Wynn Jacobson-Galán, co-author of the work.
Referencia: W. V. Jacobson-Galán et al. Final Moments. I. Precursor Emission, Envelope Inflation, and Enhanced Mass Loss Preceding the Luminous Type II Supernova 2020tlf. The Astrophysical Journal, 2022; Volume 924, Number 1
