Astronomers discover origin of thermonuclear supernova explosion

A recent publication in the esteemed journal Nature presents a groundbreaking revelation about the genesis of thermonuclear supernova explosions. Astronomers from Stockholm University have shed light on the origins of these cataclysmic events by studying the emission lines of helium and making the first-ever detection of a supernova of this type in radio waves. Their findings indicate that the white dwarf star responsible for the explosion had a companion star rich in helium.

Type Ia supernovae are of particular significance to astronomers as they serve as crucial tools for measuring the expansion of the universe. However, the exact mechanisms and nature of their progenitors have long eluded scientists. While it is known that the explosions originate from compact white dwarf stars that have accreted an excessive amount of matter from a companion, the precise process has remained elusive. The recent discovery of supernova SN 2020eyj has provided a breakthrough in this field by establishing that the companion star in this particular event was a helium star that had recently shed a substantial portion of its material just before the white dwarf's explosion.

Erik Kool, a post-doctoral researcher from the Department of Astronomy at Stockholm University and the lead author of the paper, elaborates on their approach: “Upon observing the distinct signatures of a vigorous interaction with material from the companion star, we endeavored to detect the same in radio emissions. The radio detection represents a significant milestone as it marks the first-ever observation of a Type Ia supernova in this wavelength range—a goal astronomers have pursued for decades.”

Supernova 2020eyj was initially discovered by the Zwicky Transient Facility camera located on Palomar Mountain, with the involvement of the Oskar Klein Center at Stockholm University as one of its participating institutions.

Animation of a supernova explosion. Credit: Adam Makarenko/W. M. Keck Observatory

Professor Jesper Sollerman, a co-author of the paper from the Department of Astronomy, emphasizes the pivotal role played by the Nordic Optical Telescope on La Palma in tracking the progress of this supernova. He also highlights the invaluable contribution of spectra obtained from the renowned Keck Telescope located in Hawai'i, which swiftly revealed the exceedingly uncommon presence of helium-dominated material surrounding the exploded star.

“This Type Ia supernova is undeniably extraordinary, yet it remains connected to the supernovae we employ for measuring the universe's expansion,” asserts Joel Johansson from the Department of Physics.

Johansson further elaborates, “While conventional Type Ia supernovae typically exhibit uniform brightness during their explosions, this particular supernova informs us that there exist numerous distinct paths leading to the explosion of a white dwarf star.”

Source: Stockholm University

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