There are a variety of theories about how our solar system could have formed. But at the moment, scientists have not yet come to a general agreement and a model that could explain all the features and oddities associated with it. To the collection of such theories can be added the latest work of researchers from the University of Chicago, who argue that their model is able to explain very unusual aspects associated with the early history of our system.
According to a common theory, our solar system was formed several billion years ago as a result of a supernova explosion, the effects of which triggered some processes in the gas and dust nebula, from which our Sun later appeared.
However, according to the new proposed model, it all started thanks to the explosion of a Wolf-Rayet star, which was 40-50 times larger than our current Sun in size. The stars of this class are considered one of the hottest. In addition, stars of this class are believed to produce massive amounts of chemical elements that are ejected from their surface by strong stellar winds. As the Wolf-Rayet star loses its mass, its stellar wind "churns" the chemical elements around it, eventually forming a dense bubble.
A computer model shows how stellar winds carry mass from the surface of a giant star and form bubbles around it over millions of years.
"The shell of such a bubble and the dust and gas accumulating underneath is an ideal environment for the production of new stars," said study co-author Nicholas Doffas, professor in the Department of Geosciences at the University of Chicago.
Researchers believe that approximately one to sixteen percent of all sun-like stars could have appeared in such "stellar nurseries."
The new model of the formation of the solar system is very different from the hypothesis in which the progenitor of our sun is considered a supernova explosion. Yet it is able to explain one obscure aspect that other theories cannot explain. The aspect is quite significant, as it significantly distinguished our young system from the rest of our galaxy. In particular, we are talking about the unusual proportion of some isotopes that were available in our system in its early times: the isotope of aluminum-26, which was much more than everywhere else (meteorites that remained from the days of the young solar system told us about its presence), and also the isotope of iron-60, of which there was much less, as evidenced by the results of earlier studies in 2015.
This led scientists to some questions, because supernovae produce the same amount of both isotopes.
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"We asked ourselves: why is there a difference in the volume of these isotopes in our solar system, if the supernova was supposed to supply them with the same amount?"
Thus, the researchers eventually came to the Wolf-Rayet stars, which produce a lot of the isotope aluminum-26, but not iron-60.
“We assume that the aluminum-26 isotope produced by the Wolf-Rayet star was ejected towards the outer edge of the bubble on dust particles that accumulated around the star. These particles received enough momentum and were thrown through the shell, but most of them broke against the shell, sealing the aluminum isotope inside it,”says Dwarkadas.
In the end, under the influence of the star's gravity, part of the shell collapsed, which launched the process of the beginning of the formation of our solar system.
A slice of a model showing how bubbles evolve around massive stars over millions of years (watch clockwise from the top left of the image) As for the fate of the Wolf-Rayet star itself, it remains a mystery to researchers. It is very likely that her life ended as a result of a supernova explosion or direct collapse into a black hole. But in both cases, it would be about the production of a small amount of the isotope iron-60.
Nikolay Khizhnyak