Traces Of A Devastating Primordial Supernova (Cosmology)

Identified chemical traces of the explosion of an ancient high-energy supernova in a second generation star, named AS0039, present in the Sculptor dwarf galaxy The result is the result of a research led by two researchers from the University of Florence associated with the National Institute of Astrophysics

Deep in time, when the universe was still a child, about 13.5 billion years ago, the first stars appeared from a calm and dark sea made up of only hydrogen and helium. It is thought that they were more massive stars than our Sun, therefore destined to die by exploding as supernovae and spreading the first heavy chemical elements forged during their evolution into the surrounding environment: carbon, oxygen, iron, zinc … The search for traces of the first stars it is today one of the most fascinating frontiers of astrophysics and cosmology. From the gas enriched with chemical elements deriving from the explosion of those first stars, second generation stars were born. Of the latter, low-mass stars have survived to the present day.

The international research published on July 13 in The Astrophysical Journal Letters by a team, led by the University of Florence, which has led to the identification of the chemical traces of the explosion of a first supernova, of very high energy, falls within this framework. a second generation star, named AS0039, present in the Sculptor dwarf galaxy , which gravitates around the Milky Way. The chemical signature of this type of energetic primordial supernovae is an absolute novelty for scholars.

Artist’s impression of the first stars to appear in the universe. Credits: Nasa / Wmap Science Team

“At other times, research has proven, through the study of the chemical traces of second generation stars, the existence of primeval stars, but so far all the data analyzed have indicated that the primordial progenitor star exploded with a low explosion energy”, explain Asa Skuladottir and Stefania Salvadori , from the Department of Physics and Astronomy of the University of Florence and associated with the National Institute of Astrophysics (Inaf), who guided the work. «In this case, however, we are in the presence of a secondary star with exceptional chemical characteristics: low in iron, AS0039 is not even rich in carbon and has an extremely low amount of magnesium compared to other heavier chemical elements, such as calcium. In essence, it is the poorest star in heavy chemicals ever discovered outside our galaxy. The explanation of its uniqueness is that the very ancient stellar fossil studied was formed in an environment enriched by the chemicals released by a first star of about 20 solar masses exploded as a hypernova , i.e. with an energy 10 times higher than that of normal supernovae. of similar mass “.

“To achieve this fundamental result”, continues Salvadori, winner in 2018 of an ERC starting grant for the Nefertiti project on the origin of the first stars and the first galaxies, “we used the method of high resolution spectroscopy and they were analyzed further 16 thousand models of first-star enrichment. The research also involved researchers from Sweden, Holland, Great Britain, France and Spain, and leads to a fundamental acquisition: the study shows that the analysis of stellar fossils allows us not only to indirectly determine the mass of the first stars, but also it also provides crucial information about the energy of the first supernova explosions. And therefore on the first steps of the universe ».

Featured image: Sculptor dwarf galaxy. Credits: Eso / Digitized Sky Survey 2

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