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Collisions of neutron stars enrich the universe more than the merging of black holes with stars

Scientist of the MIT from LIGO and the University of New Hampshire calculated the amount of heavy elements produced when black holes merge with neutron stars and compared their data with the amount of heavy elements produced when neutron stars merge. Hsin-Yu Chen, Salvatore Vitale and Francois Foucart used advanced simulation systems and data from the Gravitational wave observatories LIGO-Virgo.

Currently, astrophysicists do not fully understand how elements heavier than iron form in the universe. They are believed to arise in two ways. About half of these elements are formed during the process s in stars of low mass (0,5-10 solar masses) in the final stages of their life. They are then red giants. There takes place Nucleosynthesis instead of when fast Neutrons be captured by nuclides with low neutron density and medium temperatures.

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The other half of the heavy elements, on the other hand, are created quickly r process, for supernovae and kilonova explosions. Then there is a rapid capture of many neutrons, followed by a series of decays that lead to the formation of a stable element. This process requires high temperatures and very dense neutron flows. However, scientists argue about where the r-process takes place.

In 2017 LIGO-Virgo signed a Neutron star merger on leading to a huge explosion, called a kilonova, led. At that time, it was confirmed that heavy elements were formed in this process. However, there is a possibility that the r-process also occurs immediately after a neutron star merges with a black hole.

The scientists suspect that when a neutron star is torn apart by the Gravitational field The black hole throws a huge amount of neutron-rich material into space. However, the experts point out that this process must be a black hole with a relatively low mass that rotates very quickly. A black hole that is too massive will very quickly become material from the Neutron star absorb, and little will end up in space.

Chen, Vitale and Foucart were the first to introduce the crowd heavy elements compared that arise in both types of r-processes. In doing so, they tested numerous models according to which the r-process could run.

Most of the simulations showed that over the past 2,5 billion years space was enriched by 2 to 100 times more heavy elements from the merging of neutron stars than from collisions between black holes and neutron stars. In models in which the black hole rotated slowly, the amalgamation of Neutron stars twice as many heavy elements as the fusion of the black hole and neutron star. On the other hand, when neutron stars merge, where the Black hole rotates slowly and has a low mass - less than 5 solar masses - up to 100 times more heavy elements than in the r-process. The data we currently have, however, tend to rule out the existence of such black holes.

The study's authors are already planning to use data from LIGO, Virgo and the new Japanese KAGRA detector to improve. All three instruments should be ready for use again next year. More precise calculations of the production rate of heavy elements in the universe will be useful, among other things, to better determine the age of distant galaxies.