Astronomers capture red supergiant's death throes
`For the first time, we watched a red supergiant star explode,'
researcher says

Date:
January 6, 2022
Source:
Northwestern University
Summary:
Astronomers previously believed that red supergiant stars fell
dormant at the end of their lives. A new study shows that red
supergiant stars can violently erupt before collapsing into
supernovae


FULL STORY ==========================================================================
For the first time ever, astronomers have imaged in real time the
dramatic end to a red supergiant's life -- watching the massive star's
rapid self- destruction and final death throes before collapsing into
a type II supernova.


==========================================================================
Led by researchers at Northwestern University and the University of
California, Berkeley (UC Berkeley), the team observed the red supergiant
during its last 130 days leading up to its deadly detonation.

The discovery defies previous ideas of how red supergiant stars evolve
right before exploding. Earlier observations showed that red supergiants
were relatively quiescent before their deaths -- with no evidence of
violent eruptions or luminous emissions. The new observations, however, detected bright radiation from a red supergiant in the final year before exploding. This suggests at least some of these stars must undergo
significant changes in their internal structure, which then result in
the tumultuous ejection of gas moments before they collapse.

"This is a breakthrough in our understanding of what massive stars do
moments before they die," said Wynn Jacobson-Gala'n, 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 discovery
was published today (Jan. 6) inThe Astrophysical Journal.

Although the work was conducted at Northwestern, where Jacobson-Gala'n
was a National Science Foundation (NSF) Graduate Research Fellow, he
has since moved to UC Berkeley. Northwestern co-authors include Deanne Coppejans, Charlie Kilpatrick, Giacomo Terreran, Peter Blanchard and
Lindsay DeMarchi, who are all members of Northwestern's Center for Interdisciplinary and Exploratory Research in Astrophysics (CIERA).



========================================================================== 'We've never confirmed such violent activity' The University of Hawai?i Institute for AstronomyPan-STARRS on Haleakal?, Maui, first detected
the doomed massive star in summer 2020 via the huge amount of light
radiating from the red supergiant. A few months later, in fall of 2020,
a supernova lit the sky.

The team quickly captured the powerful flash and obtained the very first spectrum of the energetic explosion, named supernova 2020tlf (SN 2020tlf)
using the W.M. Keck Observatory's Low Resolution Imaging Spectrometer on Maunakea, Hawai?i. The data showed direct evidence of dense circumstellar material surrounding the star at the time of explosion, likely the same
gas that Pan- STARRS had imaged the red supergiant star violently ejecting earlier in the summer.

"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." The team continued to monitor SN 2020tlf after the explosion. Based on data obtained from Keck Observatory's Deep Imaging
and Multi-Object Spectrograph and Near Infrared Echellette Spectrograph,
the researchers determined SN 2020tlf's progenitor red supergiant star -- located in the NGC 5731 galaxy about 120 million light-years away from
Earth -- was 10 times more massive than the sun.



========================================================================== Remote possibilities Margutti and Jacobson-Gala'n conducted most of
the study during their time at Northwestern, with Margutti serving as
an associate professor of physics and astronomy and member of CIERA,
and Jacobson-Gala'n as a graduate student in Margutti's research
group. Margutti is now an associate professor of astronomy and
astrophysics at UC Berkeley.

Northwestern's remote access to Keck Observatory's telescopes was integral
to their research. From the University's Evanston campus, astronomers
can connect with an on-site telescope operator in Hawai?iand choose
where to position the telescope. By bypassing long-distance travel to
Hawai?i, astronomers save precious observing time -- often catching
transient events like supernovas, which can quickly flare up and then
swiftly vanish.

"This significant discovery of a red supergiant supernova is yet one more strong indication of the importance of Northwestern's investment in access
to top private telescope facilities, including the Keck Observatory," said Vicky Kalogera, the Daniel I. Linzer Distinguished University Professor
of Physics and Astronomy at Northwestern's Weinberg College of Arts and Sciencesand director of CIERA. "The Keck telescopes, currently the best
on our planet, uniquely enable scientific advances of this caliber as
CIERA researchers have shown since our Keck partnership started just
a few years ago." Margutti, Jacobson-Gala'n and their Northwestern
co-authors are members of the Young Supernova Experiment, which uses
the Pan-STARRS telescope to catch supernovae right after they explode.

"I am most excited by all of the new 'unknowns' that have been unlocked
by this discovery," Jacobson-Gala'n said. "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."
The study was supported by NASA, the National Science Foundation, the
Heising- Simons Foundation, the Canadian Institute for Advanced Research,
the Alfred P.

Sloan Foundation and VILLUM FONDEN.

========================================================================== Story Source: Materials provided by Northwestern_University. Note:
Content may be edited for style and length.


========================================================================== Related Multimedia:
* Video_of_a_red_supergiant_exploding ========================================================================== Journal Reference:
1. W. V. Jacobson-Gala'n 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 [abstract] ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220106143653.htm

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