Scientists have created the first-ever simulation of the process of merging binary neutron stars. This will help to understand how dark matter behaves.

Simulations will help test theories that go beyond general relativity, such as reproducing the behavior of dark energy. This will allow us to compare Einstein’s theory and its modified versions, and if we have enough accurate data, it can unravel the mystery of dark energy.

For about 100 years, the general theory of relativity has been a good description of gravity in various regimes. But in order to explain, for example, the accelerated expansion of the Universe, it is necessary to introduce some corrections into the theory, for example, to take into account such components as dark matter and dark energy, which are still a mystery.

Enrico Barausse, an astrophysicist at SISSA (International Graduate School of Awanzati Studies) and Principal Investigator of the ERC GRAMS (Gravity from Astrophysical to Microscopic Scales) grant, wonders if dark energy is real or if it is a disruption in how we understand gravity.

The existence of dark energy may just be an illusion. The accelerated expansion of the Universe can be caused by some as yet unknown modifications of the general theory of relativity, a kind of “dark gravity”.

Enrico Barausse, SISSA astrophysicist

The merger of neutron stars is a unique situation that allows you to test this hypothesis, since the gravity around them is in an extreme state.

Neutron stars are the densest stars in existence, typically up to 10 km in radius, but with a mass one or two times that of the Sun. This makes the gravity and space-time around them extreme. There is an active generation of gravitational waves when two of them collide. We can use data from such events to study how gravity works and test Einstein’s theory.

Enrico Barausse, SISSA astrophysicist

Through these simulations, researchers are finally able to compare general relativity and modified gravity.

Surprisingly, we have found that the “dark gravity” hypothesis is just as well suited as general relativity to explain the collision process of binary neutron stars. Indeed, the differences between the two theories in these systems are quite subtle, but they can be found with the next generation gravitational interferometer, such as the Einstein telescope in Europe. This will help to use gravitational waves to distinguish between dark matter and “dark gravity”.

Enrico Barausse, SISSA astrophysicist

The authors note that their discovery will help to use gravitational waves to distinguish between dark matter and “dark gravity.”