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In a discovery that could upset our understanding of the origin of Earth's heavy elements, such as gold and platinum, new research done by a physicist at the University of Guelph suggests that the most of them have been vomited by a sort of star explosion largely ignored, distant in time and space. of our planet.
Some 80% of the heavy elements of the universe have probably formed in collapses, a rare but heavy form of supernova explosion resulting from the gravitational collapse of ancient and massive stars, usually 30 times heavier than our sun, said physics professor Daniel Siegel.
This finding reverses the widely held belief that these elements came mainly from collisions between neutron stars or between a neutron star and a black hole, Siegel said.
His article co-authored with colleagues from Columbia University is published today in the journal Nature.
Using supercomputers, the trio simulated the dynamics of collapsars, or old stars whose gravity causes their implosion and the formation of black holes.
According to their model, massive, rapidly rotating collapsies reject heavy elements whose quantities and distribution "look amazingly similar to what we observe in our solar system," said Siegel. He joined the UG this month and was also appointed to the Perimeter Institute for Theoretical Physics in Waterloo, Ontario.
Most of the elements found in nature were created by nuclear reactions in stars and were finally expelled by huge stellar explosions.
Heavy elements found on Earth and elsewhere in the universe, from old explosions, range from gold and platinum to uranium and plutonium used in nuclear reactors, to more exotic chemical elements, such as as neodymium, present in consumer goods such as electronics.
Until now, scientists thought that these elements were mainly made up of stellar smashups involving neutron stars or black holes, as in a collision of two neutron stars observed by earth-bound detectors who made the headlines in 2017.
Ironically, said Siegel, his team began working to understand the physics of this merger before their simulations point to collapses as a birth chamber of heavy elements. "Our research on neutron star mergers led us to think that the birth of black holes in a very different kind of stellar explosion could produce even more gold than mergers. neutron stars. "
What collapsars lack of frequency, they compensate for the generation of heavy elements, said Siegel. Collapsars also produce intense gamma ray lightning.
"80% of these heavy elements that we see should come from collapsars." Collapsars are quite rare in supernova occurrences, even rarer than neutron star mergers – but how much material do they have? eject in the space is far superior to that derived from star neutrons mergers. "
The team now hopes to see its theoretical model validated by observations. Siegel said infrared instruments such as those of the James Webb Space Telescope, which is scheduled for launch in 2021, should be able to detect revealing radiation pointing to heavy elements coming from a collapsar located in a far-off galaxy.
"It would be a clear signature," he said, adding that astronomers could also detect collapses by examining the amount and distribution of heavy elements in other stars of our galaxy, the Pathway. Milky.
Siegel said this research could provide clues to the beginning of our galaxy.
"Trying to determine where the heavy elements come from can help us understand how the galaxy was chemically assembled and how it was formed." It could actually help solve some of the big questions in cosmology because the heavy elements are a good tracer. "
This year marks the 150th anniversary of the creation of the periodic table of chemical elements by Dmitri Mendeleiev. Since then, scientists have added many other elements to the periodic table, a basic element of textbooks and science classes around the world.
Speaking of the Russian chemist, Siegel said: "We are familiar with other elements that he did not know.What is fascinating and surprising is that after 150 years of In studying the fundamental elements of nature, we still do not understand how to create a large fraction of the elements of the periodic table. "
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