Rare supernova challenges old theories, reveals secrets of dying giant star

DNVN - A rare cosmic explosion has been discovered that has given scientists an unprecedented look at the internal structure of a giant star. This event not only challenges long-standing astronomical theories, but also opens up a new direction of research into how massive stars end their lives.

Revealing the hidden core with silicon and sulfur

The supernova, SN2021yfj, revealed the stripped-down core of a massive star, exploding with unusual amounts of silicon and sulfur. Unlike typical supernovae, the event showed a unique chemical signature unlike anything previously observed.

An international collaboration led by astrophysicists at Northwestern University (USA) has identified this as a completely new type of supernova, containing unusually high levels of silicon, sulfur and argon.

Normally, when massive stars collapse, scientists find traces of hydrogen and helium. However, SN2021yfj revealed heavier elements that were thought to be deep inside, challenging the old theory of the "onion" structure of massive stars.

SN 2021yfj is a new type of supernova that challenges our understanding of stellar evolution. Its progenitor star lost its outer layers long before the supernova, leaving behind only an oxygen/silicon core — unlike any known star in the Milky Way. Credit: WM Keck Observatory/Adam Makarenko

Bright explosion 2.2 billion light years from Earth

According to the researchers, the progenitor star of SN2021yfj went through two periods of extreme instability, shedding shells rich in silicon, sulfur, and argon. The violent collision of these layers created a bright supernova, still visible from a distance of 2.2 billion light years.

What's special is that SN2021yfj is classified in a completely new class – Type Ien, and it's possible that the star itself hasn't been completely destroyed.

Observations indicate that the star shed its outer layers of hydrogen, helium, and carbon, exposing regions rich in silicon and sulfur before exploding. This is the first time scientists have had a direct look at the long-anticipated inner shell. The results of the study were published in the journal Nature on August 20.

“This is the first time we’ve seen a star stripped all the way to its core. It shows that stars don’t just lose their outer layers, but can strip almost all of their outer layers before exploding brilliantly,” said researcher Steve Schulze of Northwestern University.

Challenging old theories

“This event is unlike anything we’ve ever seen,” said study co-author Adam Miller. “It shows that our current theories of stellar evolution are too narrow. It’s not that the textbooks are wrong, but they’re clearly incomplete. There may be exotic pathways that we haven’t thought of.”

Supernova SN2021yfj was discovered by Schulze and his colleagues in September 2021 using data from the Zwicky Transient Facility (ZTF) in California. The team then collected spectra using telescopes at the W. M. Keck Observatory in Hawaii, which helped decipher the elements present in the explosion.

Instead of familiar traces like helium, carbon, or oxygen, SN2021yfj's spectrum is dominated by strong signals of silicon, sulfur, and argon—elements that only form deep in the core of giant stars.

Researchers believe the explosion may have been caused by the star tearing itself apart during a period of extreme instability. This resulted in shells being continuously ejected, colliding and creating the bright radiation observed.

“We only have one example, SN2021yfj. It is a reminder that the universe is full of strange phenomena, forcing us to continue to search and study,” scientist Adam Miller emphasized.

La Khe (According to SciTechDaily)

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