When a neutron star collide with another neutron star or a black hole, spacetime vibrates and energy is released in gravitational waves. These gravitational waves propagate through the universe at the speed of light and, once captured by gravitational-wave observatories like LIGO and Virgo and—in the future—the Einstein Telescope, are witnesses to the energetic events that created them. The collision also results in the ejection of matter into space, which produces electromagnetic radiation like gamma rays, X-rays, and visible light detectable by ground-based observatories like ESO’s Very Large Telescope and space-based observatories like NASA’s James Webb Space Telescope.

Where do rare earth metals and gold originate?

Gravitational and electromagnetic waves from neutron star mergers provides us with information about extreme physical conditions that cannot be reproduced on Earth itself. One example of this is the as yet unknown origin of rare earth elements and metals such as gold in the universe, which are probably formed during such mergers.

?The prerequisite for breakthrough discoveries is that we can read and correctly interpret the information in the gravitational waves and electromagnetic counterparts,? says Prof. Dr. Sebastiano Bernuzzi from the University of Jena. ?Although these different signals can now be detected together, comprehensively analysing them to answer fundamental physics questions remains a challenge,? explains the professor of theoretical physics and gravitational theory.

Together with colleagues at Pennsylvania State University in the United States, he has launched a new research project that addresses precisely this issue. Entitled ?Multimessenger Astronomy of Neutron Star Mergers with Numerical Relativity?, the project aims to develop the theoretical framework necessary for interpreting future observations. It is being carried out as part of the ?NSF-DFG Funding Opportunity for Collaborations in Physics? programme, receiving approximately 300,000 euros of funding from the German Research Foundation at the University of Jena.

A publicly accessible database with 1,000 simulations

A key aspect of the project involves creating a publicly accessible database comprising approximately 1,000 simulations of neutron star and black hole-neutron star mergers. The research will explore a variety of merger conditions such as the mases of the colliding objects and whether they are predominantly composed of traditional particles like protons and neutrons or more exotic particles like quarks. Simulation data and models will provide a theoretical basis for interpreting future merger observations, for example, by predicting how much matter is ejected by binaries with different masses, the properties of the merging objects and the characteristic signatures in the gravitational waves.

The project will train doctoral students in relativistic astrophyscics, numerical general relativity and fluid mechanics, high-performance computing and machine learning. ?The team and project will greatly benefit of the complimentary expertise in the two groups?, expects Prof. Bernuzzi. ?Additionally, the grants will also allow master student exchanges between the two universities, thus providing a great opportunity for undergraduate to experience different research environments and lifestyles.?