The prediction from 1989 that came true and the rapid mobilization of astrophysicists to observe the source of gravitational waves with other detectors as well

Prof. Zvi Piren from the Hebrew University, who predicted what might happen when two neutron stars collide, and Prof. Dobi Ponzanansky from Tel Aviv University, who represents the experimental astronomers, are interviewed for the science site following the combined discovery of gravitational waves, gamma radiation, and electromagnetic radiation simultaneously from the same event

The event in which two neutron stars collided whose gravitational waves reached the Earth on August 17, 2017 is a defining event in the field of astrophysics. As you remember, the two detectors of an American project called LIGO and a European detector called Virgo picked up gravitational waves from the event of the merger of two neutron stars somewhere in the universe, and at the same time the massive explosion was observed with the help of a large variety of telescopes on Earth and in space.

It interests both the theoretical astrophysicists and of course the experimenters - those who sit on the output of the instruments observing the event - from the giant LIGO and VIRGO detectors that discovered the gravitational waves and located the galaxy from which they came, to space telescopes and of course every ground telescope that could observe the source in the coming days the event

Quite a few Israeli researchers participated in the global effort. Professors Dan Maoz Ehud Neker Dobi Poznansky and Yair Harkabi from Tel Aviv University, Professors Assaf Sternberg and Zvi Piren from the Hebrew University, as well as Prof. Avishai Gal-Yam and Eran Ofek at the Weizmann Institute and many others.
Piren and Necker deal with the theoretical aspects of the phenomenon from different directions, Maoz Poznansky and Harkabi deal with processing observations in the visible field, Sternberg investigates the event in the field of radio radiation.

This diversity is indicative of the general diversity of astrophysicists around the world who took part in the effort to observe the event with all possible detectors.

Prof. Piren predicted in an article he wrote with partners and which was published in the journal Nature in 1989, he predicted the sequence of events and what type of radiation would reach the earth following it and at what speed, and also predicted the origin of the heavy elements in the universe, among other things, in events involving neutron stars.

"In an article in 1989 in Nature, I and a number of other researchers proposed that in neutron star collisions, in addition to gravitational waves, gamma waves and rare metals are also created, and indeed this is what was discovered after observing the gravitational waves and then the gamma radiation flash and finally optical and infrared radiation that arrived for weeks from each The heavy elements thrown into space.”
"In the last stages of the current event, I was involved in three different groups that made observations of this system, both in the radio field and in visible light. Two of the articles were published in the journal SCIENCE and the third in Nature. In addition to this, immediately after the publication of the dozens of articles, I together with a group of researchers from Tel Aviv University, headed by Prof. Neker, sent two theoretical articles that give a detailed explanation of what we think happened exactly. Although we predicted the event 29 years ago, there are still some differences. We explained the differences between the observations and what the forecast was, we explained why the gamma radiation was a little weaker than what was expected and why the visible light radiation was a little stronger in the first days, here too there is an interesting curiosity because in May of this year, a few months before the event, Ehud Necker and his student Or Gottlieb published We published an article that was accepted for publication before the discovery that explains that there will be weaker events than the usual explosions and this is exactly what they predicted this time."
"The current event had three components, each of which came from a different research field in astrophysics. The gravitational waves testified that there was a merger of two neutron stars and that a black hole was probably created in the merger process. The flash of gamma radiation indicated that the merger of two neutron stars emitted into outer space jets of matter moving at a speed close to the speed of light. In contrast, the visible light and infrared radiation that followed showed us that we were seeing the heavy materials thrown into outer space. We proposed that the origin of the heavy elements in the universe is in such collisions and indeed the visible light and especially the infrared light that came about 4-5 days after the explosion showed that heavy substances characterized by high opacity were formed there. In other words, there are three pieces of the puzzle that each indicate different outcomes of the collision."

Prof. Dobi Ponzanansky was also interviewed by the Hedaman website following the wave of scientific publications surrounding the event. "I am excited by the sociological aspect surrounding the event, it was good to see the mobilization of the astrophysical community - every telescope that could be pointed in the general direction and the effort of thousands of people from dozens of groups around the world. Thanks to this effort we learned a lot of new things. I will have to spend the next few weeks only from what was published this week. There has never been a massive release of such a large number of papers in one day, unprecedented in science, it can even be said that it is part of the new era in science.

"The main thing we learned from this event is another layer on the formation of the heavy elements in the universe that for a long time it was not clear where they were formed. Until now, it was estimated that they occurred in supernovae, but it was not clear if there were conditions for the rapid enrichment of the elements by the neutrons. So far we have evaluated this from the theoretical point of view. Now we can see this at least indirectly thanks to the properties measured in the event.”
According to him, apparently the nature of the galaxy where the collision occurred has an effect on it. Since the convergence between the neutron stars is slow, the likelihood is that this will happen in old galaxies, and indeed the galaxy is one that has already stopped producing new stars, which indicates its high age."

See more on the subject on the science website:

• For the first time, gravitational waves and light waves were discovered from the same event - the merger of two neutron stars (Tel Aviv University)
• For the first time, a collision and merger of two neutron stars was observed (Weizmann Institute)
• Einstein - the man who started to take us out of the matrix: there are gravitational waves!
• Nobel Prize in Physics for the discovery of gravitational waves
• "The winners of the Nobel Prize in Physics were themselves surprised by the strength of the signal of the first gravitational wave event"
• A collaboration between three observatories resulted in another discovery of gravitational waves
• A new detector will determine the origin of gravitational waves
• A third gravitational wave event has been discovered; Confirms the existence of a new type of black holes
• Proof of Einstein's theory of general relativity: "The discovery of gravitational waves opens a new window to the universe"