A depiction of the artist showing the simulation of two merging neutron stars (left) and emerging traces of particles that can be seen in a heavy ion collision (right), which creates matter under similar conditions in the laboratory. Credit: Tim Dietrich, Arno Le Fevre, Keys Huyzer; background: ESA / Hubble, Sloan Digital Sky Survey
Combining experiments with heavy ions, astrophysical observations and nuclear theory.
When a massive star explodes into a supernova, if not completely destroyed, it will leave behind either a black hole or a neutron star. These enigmatic space objects are especially mysterious because of the crushing internal pressure resulting from the incredible density of neutron stars and the confusing properties of the nuclear matter from which they are made.
Now, for the first time, an international team of researchers is combining data from heavy ion experiments, gravitational wave measurements and other astronomical observations, using advanced theoretical modeling to more accurately limit the properties of nuclear matter that can be found inside neutrons. stars. The results were published on June 8, 2022 in the journal Nature.
Neutron stars form when a giant star runs out of fuel and collapses. They are among the densest objects in space, with a piece the size of a cube weighing 1 billion tons (1 trillion kg).
Throughout the universe, neutron stars are born in supernova explosions that mark the end of the lives of massive stars. Sometimes neutron stars are connected in binary systems and will eventually collide with each other. These high-energy astrophysical phenomena are characterized by such extreme conditions that they produce most of the heavy elements, such as silver and gold. Therefore, neutron stars and their collisions are unique laboratories for studying the properties of matter at densities far exceeding the densities in atomic nuclei. Heavy ion collision experiments with particle accelerators are an additional way to produce and study matter at high densities and under extreme conditions.
New insights into the fundamental interactions in nuclear matter
“Combining knowledge of nuclear theory, nuclear experiment and astrophysical observations is essential for shedding light on the properties of neutron-rich matter across the density range studied in neutron stars,” said Sabrina Hutt, Institute of Nuclear Physics at the Technical University. University of Darmstadt, which is one of the leading authors of the publication. Peter TH Pang, another lead author at the Institute for Gravitational and Subatomic Physics (GRASP), University of Utrecht, added: “We find that the limitations of collisions of gold ions with particle accelerators show remarkable consistency with astrophysical observations, although with completely different methods. “
Artistic image of a neutron star. Credit: ESO / L. Calçada
Recent advances in astronomy with many reports have allowed an international research team of researchers from Germany, the Netherlands, the United States and Sweden to gain new insights into the fundamental interactions in nuclear matter. In an interdisciplinary effort, the researchers included information from heavy ion collisions in a framework that combines astronomical observations of electromagnetic signals, gravitational wave measurements and high-performance astrophysical calculations with theoretical calculations of nuclear physics. Their systematic study combines all of these individual disciplines for the first time, pointing to higher pressures at intermediate densities in neutron stars.
Heavy ion collision data are included
The authors included information from gold ion collision experiments conducted at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, as well as the Brookhaven National Laboratory and the Lawrence Berkeley National Laboratory in the United States in their multi-stage procedure that analyzes limitations from nuclear theory. measurements of neutron star mass by radio observations, information from the International Space Station (ISS) neutron star mission (NICER) and observations with multiple messengers of binary neutron star mergers.
Nuclear theorists Sabrina Hutt and Achim Schwenk of the Technical University of Darmstadt and Ingo Tus of the Los Alamos National Laboratory were key to translating the information from heavy ion collisions into neutron star matter, which is needed to include astrophysics.
The inclusion of heavy ion collision data in the analyzes has allowed for additional limitations in the area of density, where nuclear theory and astrophysical observations are less sensitive. This helped to provide a fuller understanding of dense matter. In the future, improved restrictions on heavy ion collisions may play an important role in linking nuclear theory and astrophysical observations by providing additional information. Especially experiments that investigate higher densities while reducing experimental uncertainty have great potential to provide new constraints on neutron star properties. New information from both sides can easily be included in the framework to further improve the understanding of dense matter in the coming years.
Reference: “Limiting the matter of the neutron star by microscopic and macroscopic collisions” by Sabrina Hutt, Peter T.H. Pang, Ingo Tus, Tim Dietrich, Arno Le Fevre, Achim Schwenk, Wolfgang Trautmann, Krziti Agarwal, Matthias Bula, Michael W. Coughlin and Chris. Van Den Broeck, June 8, 2022, Nature.DOI: 10.1038 / s41586-022-04750-w
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