Rare earth elements may be produced during neutron star mergers

(ORDO NEWS) — Japanese and European astronomers have found that neutron star mergers lead to the formation of superheavy atoms from the lanthanide group, which includes cerium, neodymium and many other important rare earth metals.

“For the first time, we have managed to detect traces of rare earth elements in the spectrum of a flare generated by the merger of neutron stars.

This discovery significantly expands our understanding of the process of the chemical evolution of the Universe,” said Nanae Domoto, a researcher at the University of Tohoku (Japan), whose words are quoted by the CfCA press service.

Today, physicists believe that all elements heavier than iron, including gold, uranium, and other heavy and rare earth metals, originated in large part as a result of supernova explosions, since the temperature and pressure inside “normal” stars are too low for their rapid formation. .

Subsequently, scientists discovered that supernova explosions could not produce the required amount of some astronomical “metals”, elements heavier than helium and hydrogen.

For this reason, theorists have suggested that other, more exotic processes, such as neutron star collisions, were involved in the formation of these elements.

Chemical evolution of the universe

The first hints that this is indeed the case were received in August 2017, when the gravitational observatories LIGO and ViRGO recorded fluctuations in the fabric of space-time generated by the merger of two pulsars in the galaxy NGC 4993 in the constellation Hydra.

In the spectrum of this flash, the researchers found traces of the so-called “R-process”, a chain of thermonuclear reactions in which light nuclei are converted into gold and other heavy elements.

Domoto and her colleagues were interested in whether there are traces of other reactions in the spectrum of this cataclysm that lead to the formation of other heavy elements, including lanthanum, cerium and other metals from the lanthanide group.

Many of these substances, as scientists note, should have very bright and clear lines in the spectrum, which makes it easier to search for them in the kilonova flare generated by the merger of neutron stars.

Guided by this idea, the researchers calculated on a supercomputer what the emission and absorption lines look like for all lanthanides, and tried to find them in the data collected by orbiting infrared telescopes in August 2017 during observations of the outburst GW170817 in the galaxy NGC 4993.

As it turned out, lines associated with lanthanum and cerium were indeed present in the infrared part of the spectrum of this flare.

The number of atoms of these elements was relatively small, but the very fact of their presence suggests that neutron star mergers do generate elements from the lanthanum group, the researchers concluded.


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