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A new collision revealed a violent collision between two neutron stars 4.6 billion years ago.
Not less than 0.3% of the gold, platinum and uranium of the Earth (as well as other heavy elements) could have been forged in the fire of 39. a merger 1000 light-years away from the day before, while the solar system was more than a cloud of gas and dust.
"This means that in all of us, we would find a value corresponding to these elements," said astrophysicist Imre Bartos of the University of Florida, "primarily in the form of iodine, essential to life ".
The famous neutron star collision detected in 2017 taught us a lot, including the fact that such collisions produce heavy elements. In the electromagnetic data produced by GW 170817, scientists detected for the first time the production of heavy elements, including gold, platinum and uranium.
Indeed, a powerful explosion, such as a supernova or star meltdown, can trigger the rapid process of neutron capture, or process-r, a series of nuclear reactions in which atomic nuclei collide. with neutrons to synthesize heavier elements than iron.
Reactions must occur fast enough that the radioactive decay is unlikely to occur until more neutrons are added to the nucleus, which means that this must happen when there is a lot of free neutrons that float – like a star that explodes.
Bartos and his colleague Szabolcs Márka, of Columbia University, badyzed the radioactive isotopes present in the early meteorites of the solar system to determine the origin of the heavy elements of the Earth, that it is Act of a supernova or a fusion of neutron stars.
They are found in actinides – heavy elements whose atomic numbers range from 89 to 103, from actinium to lawrencium, all of which are radioactive; their tracks are found in the meteorites of the first days of the solar system.
Radioactive isotopes have a half-life. This refers to the period of time necessary for the disintegration of half of the atomic nuclei of a sample, a known quantity for various elements. The radioactive half-life can therefore be used as a kind of control capsule to reconstitute specific periods.
The researchers were able to use these meteorite actinides, plutonium, uranium and curium, to reconstruct the abundances of heavy elements in the early solar system.
In itself, it does not tell us much more than that. The team has therefore carried out numerical simulations of the old solar system to compare the abundances of real meteorites with those of the simulation. And they discovered that the two did not meet without a neutron star.
The best fit for the abundances observed in actinides was a collision of neutron stars about 1000 light-years from the solar system (so in the Milky Way galaxy), about 100 million years before the formation of the Earth, when the gas cloud that became the solar system was still fusing.
"If a similar event happened today at a similar distance from the solar system, the resulting radiation could overshadow the entire night sky," Márka said.
Their research revealed that this event had projected elements into the surrounding space, contributing up to 70% to the curium of the original solar system and 40% of its plutonium. Because of radioactive decay, there is much less now, 4.6 billion years later.
And he could not act from a supernova, they found – they happen far too often, putting the abundances of actinides that they would produce beyond the constraints defined by the meteorites.
The researchers said this is a result that can shed light on the processes that have shaped the solar system. And that also has an existential meaning.
"Our results respond to a fundamental quest for humanity: where do we come from and where are we going?" Said Márka.
"It is very difficult to describe the terrible emotions we felt when we realized what we had discovered and what it meant for the future, while we were looking for an explanation of our place in the Universe. . "
The search was published in Nature.
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