One hundred million light years from Earth, an unusual supernova is exploding.
That exploding star, known as the “supernova LSQ14fmg,” was the distant object discovered by a 37-member international research team led by Florida State University assistant physics professor Eric Hsiao. Their research, which was published in Astrophysical Journal, helped uncover the origins of the supernova group to which this star belongs.
The characteristics of this supernova – it gets brighter very slowly and is also one of the brightest explosions in its class – are unlike any other.
“This was a very unique and strange event, and our explanation is just as interesting,” said Hsiao, the lead author of the article.
The exploding star is what is known as a Type Ia supernova and, more specifically, a member of the “super-Chandrasekhar” group.
Stars go through some sort of life cycle and these supernovae are the explosive finale of some low-mass stars. They are so powerful that they shape the evolution of galaxies and so bright that we can observe them from Earth even in the middle of the observable universe.
Type Ia supernovae were crucial tools for discovering what is known as dark energy, which is the name given to the unknown energy that causes the universe’s current accelerated expansion. Despite their importance, astronomers knew little about the origins of these supernova explosions, other than the fact that they are the thermonuclear explosions of white dwarfs.
But the research team knew that light from a Type Ia supernova rises and falls over the course of weeks, fueled by the radioactive decay of nickel produced in the explosion. A supernova of that type would become brighter as nickel becomes more exposed, then weaker as the supernova cools and nickel decays into cobalt and iron.
After collecting data with telescopes in Chile and Spain, the research team saw that the supernova was hitting material around it, which caused more light to be released along with light from the decaying nickel. They also saw evidence of carbon monoxide production. Those observations led to their conclusion: the supernova was exploding inside what had been an asymptotic giant branch star (AGB) on its way to becoming a planetary nebula.
“Seeing how observing this interesting event fits in with the theory is very exciting,” said Jing Lu, an FSU graduate student and co-author of the paper.
They theorized that the explosion was triggered by the merger of the core of the star AGB and another white dwarf star orbiting within it. The central star was losing a significant amount of mass due to a stellar wind before the loss of mass abruptly stopped and created a ring of material surrounding the star. Soon after the supernova exploded, it hit a ring of thick material seen in planetary nebulae and produced the extra light and slow brightening observed.
“This is the first strong observational evidence that a Type Ia supernova can explode in a post-AGB or proto-planetary-nebula system and is an important step in understanding the origins of Type Ia supernovae,” said Hsiao. “These supernovae can be particularly annoying because they can mix with the sample of normal supernovae used to study dark energy. This research provides us with a better understanding of the possible origins of Type Ia supernovae and will help improve future dark energy research.” .
Shedding new light on the evolution of supernovae
E. Y. Hsiao et al, Carnegie Supernova Project II: The Slowest Rising Type Ia Supernova LSQ14fmg and Clues to the Origin of Super-Chandrasekhar / 03fg-like Events, The Astrophysical Journal (2020). DOI: 10.3847 / 1538-4357 / abaf4c
Research team discovers unique supernova explosion (2020, September 10)
recovered on 11 September 2020
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