Finally there has been official confirmation. Many years ago, in a very distant (but clearly identified, as we will explain later) galaxy two neutron stars merged to form either another “daughter” neutron star (called a “kilonova”) or even a black hole. The remaining energy of this fusion did not reach the earth until August 17, just a few days before the eclipse of the Sun, which was visible, for example, from the US.
Speaking of the Sun and neutron stars… Let us quickly remember that a neutron star is what remains after the supernova explosion of a star slightly larger than our “star king” . In this case, the electrons and protons ended up merging and forming neutrons and neutrinos. The latter escape at almost the speed of light, but the former will remain “packed together” forever, making up the heaviest and hardest objects in the cosmos.
But let’s get back to the main topic of this article. Despite overcoming many technological obstacles to be able to reach the detection of gravitational waves and having this already occurred on several occasions, there were still people skeptical of these achievements. After all, there has never been any corroboration from other observatories and / or experiments. But after the discovery, there is no longer the right to have any more doubts.
As we said and already predicted the rumors, scientists have discovered the merger of two neutron stars that occurred millions of years ago millions of light years.
But what is really interesting about this detection is that the same event has been observed both in the “spectrum of gravitational waves” and in the electromagnetic spectrum.
We also remember that the latter is the one we are already used to working on and that it involves all kinds of “light”: visible, radio, infrared, ultraviolet, gamma, etc.
Timeline of discovery
It all started on August 17 at 8:41 in the morning (US East Coast time) when LIGO detected a clear gravitational wave pattern that we have already discussed on other occasions. This signal lasted about 100 seconds (the longest to date and coinciding with the expected shape produced by the merger of two neutron stars). About two seconds later, the Fermi telescope and the Integral satellite detected an emission of gamma rays (electromagnetic spectrum).
Gamma-ray bursts have been thought to originate from merging neutron stars for many years, but there has never been clear evidence until now. Everything seems to indicate that the detection of gravitational waves by Ligo and the location of gamma rays carried out by two different telescopes came from the same cosmological event.
Unlike with black holes, light is emitted in neutron star collisions, and light is still being generated even seconds after the cataclysm has ended. Thanks to the coordination of data from Fermi, Integral and Ligo, it has been possible to specify with astonishing precision the area of space where the merger of neutron stars could have taken place.
But also, with the data from Virgo (which was already operational), this region narrowed even more: just the size that 140 full moons would have on the horizon.
A few hours later, astronomers at the VLT telescope in Chile aimed their sensors at that area of space, clearly identifying a change in the brightness of a point in the galaxy NGC 4993 : the aftermath of our neutron star merger.
In short: a new era in astronomy begins. A new era in which we are a little less “blind” to the events of the iniverse. A new era in which we combine our perfected power of vision in the electromagnetic spectrum with a new sixth sense: the talent to measure the zigzags of own space and time.
Alberto Corbi is a professor at the Higher School of Engineering and Technology (ESIT) of the International University of La Rioja (UNIR).
Image: Illustration by Robin Dienel / Carnegie Institution for Science.
