Astronomers witness huge dying star reach explosive end

Two Hawaiian telescopes capture massive star before becoming supernova

For the first time ever, astronomers have imaged the dramatic end of a red supergiant’s life in real time, observing the massive star’s rapid self-destruction and final agony before it collapses into a supernova type II.

Using two Hawai’i telescopes – the University of Hawaii Pan-STARRS Institute of Astronomy on Haleakalā, Maui and WM Keck Observatory on Maunakea, Hawai’i Island – a team of Researchers leading the Transient Investigation Young Supernova Experiment (YSE) observed the red supergiant during its last 130 days before its deadly detonation.

“This is a breakthrough in our understanding of what massive stars do moments before they die,” said Wynn Jacobson-Galán, NSF graduate researcher at UC Berkeley 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 explode!

The discovery is published in the January 6, 2022 issue of The Journal of Astrophysics.

Pan-STARRS first detected the doomed massive star in the summer of 2020 via the enormous amount of light radiating from 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 very first spectrum of the energy explosion, named 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, possibly the exact same gas that Pan-STARRS had photographed with the red supergiant star ejecting violently earlier in the summer.

An artist’s depiction of a red supergiant star transforming into a Type II supernova, emitting a violent eruption of radiation and gas on its last breath before collapsing and exploding. Credit: WM Keck Observatory / Adam Makarenko

“Keck helped provide direct evidence for the transition from a massive star to a supernova explosion,” says 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 team continued to monitor the SN 2020tlf after the explosion; on the basis of data obtained from the DEep Imaging and Multi-Object Spectrograph (DEIMOS) and the Near Infrared Echellette Spectrograph (NIRES) from the Keck observatory, they determined the red supergiant star progenitor of SN 2020tlf, located in the galaxy NGC 5731 about 120 million light-years away as seen from Earth, was 10 times more massive than the Sun.

The discovery challenges previous ideas of how red supergiant stars evolve just before they explode. Prior to that, all of the red supergiants observed before exploding were relatively calm: they showed no signs of violent eruptions or light emission, as was observed before SN 2020tlf. However, this new detection of bright radiation from a red supergiant in the last year before it explodes suggests that at least some of these stars must undergo significant changes in their internal structure which then lead to the tumultuous ejection of gas moments before their collapse.

Margutti and Jacobson-Galán conducted most of the study during their time at Northwestern University, with Margutti as associate professor of physics and astronomy and member of CIERA (Center for Interdisciplinary Exploration and Research in Astrophysics), and Jacobson-Galán as graduate student.

The team’s discovery paves the way for transient investigations such as YSE to search for light radiation from red supergiants and gather more evidence that such behavior could signal the impending disappearance of a supernova from a massive star.

“I am very excited by all of the ‘unknown’ news that has been unlocked by this discovery,” says 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 stars. last moments of their life. “

For more on this research, see Astronomers capture red supergiant star that explodes in massive supernova – for the very first time.

Reference: “Last moments. I. Precursor Emission, Envelope Swelling and Enhanced Mass Loss Preceding Type II Luminous Supernova 2020tlf ”by WV Jacobson-Galán, L. Dessart, DO Jones, R. Margutti, DL Coppejans, G. Dimitriadis, RJ Foley, CD Kilpatrick, DJ Matthews, S. Rest, G. Terreran, PD Aleo, K. Auchettl, PK Blanchard, DA Coulter, KW Davis, TJL de Boer, L. DeMarchi, MR Drout, N. Earl, A. Gagliano , C. Gall, J. Hjorth, ME Huber, AL Ibik, D. Milisavljevic, Y.-C. Pan, A. Rest, R. Ridden-Harper, C. Rojas-Bravo, MR Siebert, KW Smith, K. Taggart, S. Tinyanont, Q. Wang and Y. Zenati, January 6, 2022, The Journal of Astrophysics.
DOI: 10.3847 / 1538-4357 / ac3f3a