Only a point of light testifies to the cosmic collision
All of this occurs so far away from us that we can measure light signals, but we cannot “see” how the neutron stars orbit each other. What we observe is a point that grows brighter, i.e., a few more light particles hitting the measuring device. However, in order to view the actual structure of the star system in spatial detail, we would simply have to be closer. If we had a spaceship with a futuristic propulsion system and strong shields, we could use it to leave our galaxy and travel to such an event in another galaxy. This would be incredibly exciting because the merger of two neutron stars creates new elements that would otherwise hardly be able to form in our universe. Above all, it creates heavy elements such as gold and platinum. I would like to travel there to see how the matter is ejected during the collision, because so far we have only been able to simulate these processes on a computer. Does it really look the way we imagine it, or completely different?
But I don’t want to get too close to neutron star during the collision either – after all, you have to be careful not to be hit by the gamma-ray burst. This is a high-energy radiation that is emitted upwards and downwards relative to the plane in which the neutron stars orbit each other. Gamma-ray bursts have been studied for decades, but initially it was unclear exactly where they came from. The collision of neutron stars is one way in which they can form.
Traveling faster than the speed of light
Even if our spacecraft were flying at the speed of light, it would still take an extremely long time to reach colliding neutron stars. For comparison: the collision that we were able to see in 2017, with the help of gravitational waves as well as light, was 130 million light-years away. This means that the signals had already been travelling for 130 million years before they reached us. So we would have to set out a few hundred million years earlier to be able to see the event upon arrival. The only possibility, which is also mathematically proven, would be a warp drive that bends space so that our spaceship could effectively travel faster than light. Although the term warp drive comes from the world of science fiction, it is based on concrete physical formulas of the general theory of relativity. This would allow us to travel across space fast enough. Unfortunately, this is all just theory, and I am very skeptical that humanity will ever truly be able to put these ideas into practice.
Another point that makes the collision of neutron stars so exciting is measuring how fast the gravitational waves propagate compared to the light signal. According to Einstein’s theory of relativity, both travel at the same speed. In the 2017 event, the signals took 130 million years to reach the Earth and arrived just 1.7 seconds apart. This aligns perfectly with theoretical calculations that gravitational waves would arrive first, followed shortly by the gamma-ray burst. It was a wonderful confirmation of Einstein’s theory and thus ruled out alternative theories about gravitational waves. The simultaneous measurement of different signals opens up incredible possibilities for cosmology.
When two super heavyweights orbit each other in the universe, like black holes or neutron stars, gravitational waves are emitted. These waves compress and stretch space-time and propagate at the speed of light.
Tim Dietrich has been Professor of Theoretical Astrophysics at the University of Potsdam since 2020.
This text was published in the university magazine Portal – One 2025 “Children” (PDF).