Astrophysicists have set a new record by creating the longest and most complex simulation of neutron stars merging into a black hole with a powerful jet. The resulting artificial model opens up new possibilities for understanding some of the most energetic events in the Universe. The results of the study are published in Physical Review Letters.
The first detection of gravitational waves from colliding neutron stars in 2015 was a revolution in astronomy that marked the beginning of the era of “multi-messenger” research. This approach allows us to study the cosmos not only through light, but also through gravitational waves and neutrinos. Neutron star mergers are key events of this type, releasing gravitational waves, powerful gamma-ray bursts, and creating heavy elements such as gold or platinum. However, theoretical models of these processes still need to be refined.
Supercomputer reveals chaos
Neutron stars are the incredibly dense remnants of massive stars that exploded as supernovae. Just one teaspoon of their substance would weigh as much as Mount Everest. When two such stars merge, they generate chaos: within a critical 1.5 seconds, they collapse into a black hole, releasing streams of neutrinos and forming intense magnetic fields in the ultra-dense “nuclear paste”.
Reproducing this apocalyptic process is an incredibly difficult computational task even for today’s most powerful supercomputers. An international team of scientists used the power of the Japanese supercomputer Fugaku, applying modern physical theories. It took a colossal 130 million CPU hours to simulate just 1.5 seconds of real time using tens of thousands of cores simultaneously.
“Predicting the multi-messenger signals from binary neutron star mergers from first principles is extremely difficult. We have now succeeded in doing just that,” Kota Hayashi, a doctoral student at the Max Planck Institute for Gravitational Physics.
The birth of a black hole and a jet
The simulations showed merging neutron stars with masses of 1.25 and 1.65 solar masses. Within five mutual orbits, losing energy due to gravitational waves, the stars collided. Instantly, a supermassive neutron star was formed, which, unable to cope with its own gravity, collapsed into a black hole. Some of the matter formed an accretion disk around it.
The key result was the modeling of the birth of ultrafast jets. The intense magnetic fields of neutron stars, amplified by the rapid rotation of the black hole, accelerated matter along its spin axis.
“We think that this energy flow along the black hole axis, driven by magnetic fields, powers a gamma-ray burst,” explained Prof. Masaru Shibata, leader of the study. This provides unprecedented insight into the inner “kitchen” of the most powerful explosions in space.
We previously explained how to predict neutron star mergers.
According to iflscience.com
