Today at several simultaneous press conferences, scientists from the gravitational observatories LIGO and Virgo, as well as from other scientific institutions around the world, announced that in August this year they were able to register for the first time gravitational waves generated by the merger of two neutron stars. Previously, gravitational waves were observed by physicists four times, but in all cases they were generated by the merger of two black holes, not neutron stars.
© ESO / L. Calçada / M. Kornmesser
Moreover, also for the first time in history, the event that caused gravitational waves was noted not only by gravitational interferometer detectors, but also observed by space and ground-based telescopes in various ranges (X-ray, ultraviolet, visible, infrared and radio bands). The discovery will not only take the next step in the study of gravitational waves and gravity, but will also provide significant progress in the study of neutron stars. In particular, it confirms the hypothesis of the synthesis of heavy elements in the process of merging neutron stars and the nature of gamma-ray bursts. The discovery is described in a number of articles published in the journal Nature, Nature Astronomy, Physical Review Letters, and Astrophysical Journal Letters.
Gravitational waves are generated by any object with mass and moving with uneven acceleration, but sufficiently strong waves that can be detected with the help of devices made by man are born during the interaction of objects of very large mass: black holes, components of binary stars, neutron stars. The current wave, designated GW170817, was recorded by both detectors at the LIGO gravitational observatory in the United States and the Virgo detector in Italy on August 17 this year.
The presence of three detectors located at different points on the Earth allows scientists to roughly determine the position of the wave source. Two seconds after gravitational observatories detected wave GW170817, a gamma-ray burst was noted in the region where its source should be located. This was done by space gamma-ray telescopes Fermi (Fermi Gamma-ray Space Telescope) and INTEGRAL (INTErnational Gamma Ray Astrophysics Laboratory). After that, many ground and space observatories began to look for a possible source of these events. The area of \u200b\u200bthe search area, determined from the data of the gravitational observatory and gamma-ray telescopes, was quite large, amounting to about 35 square degrees, in such a section of the sky several hundred full lunar disks would fit, and the number of stars located on it is several million. But it was still possible to find the source of the gravitational wave and the gamma-ray burst.
The Swope reflector telescope at the Las Campanas observatory in Chile was the first to do so, eleven hours after the gamma-ray burst. After that, several large telescopes immediately interrupted their previously approved observation programs and switched to observing the small galaxy NGC 4993 in the constellation Hydra, at a distance of 40 parsecs from the solar system (about 130 million light years). This event triggered the first rumors about the discovery, but scientists have not officially confirmed anything until today's press conferences.
Indeed, the source of the waves and gamma radiation was a star located next to the galaxy NGC 4993. This star was followed for several weeks by the Pan-STARRS and Subaru telescopes in Hawaii, the Very Large Telescope of the European Southern Observatory (VLT ESO), the New Technology Telescope (NTT), VLT Survey Telescope (VST), 2.2-meter MPG / ESO telescope, ALMA (Atacama Large Millimeter / submillimeter Array) telescope array - in total, about seventy observatories from around the world participated in the observations, as well as the Hubble Space Telescope. “It is rare for a scientist to witness the beginning of a new era in science,” the ESO press release quoted astronomer Elena Pian of the Italian Astrophysical Institute INAF as saying. “This is one of those cases!” Astronomers had little time, since the galaxy NGC 4993 was available for observation only in the evening in August, in September it was too close to the Sun in the sky and became unobservable.
The observed star was initially very bright, but in the first five days of observations, its brightness decreased twenty times. This star is located at the same distance from us as the galaxy NGC 4993 - 130 million light years. This means that the gravitational wave GW170817 originated at a record distance from us. Calculations showed that the source of the gravitational wave was the merger of objects whose masses are equal from 1.1 to 1.6 times the mass of the Sun, which means that they could not be black holes. So neutron stars became the only possible explanation.
Composite image of NGC 4993
and kilonova according to many ESO instruments
© ESO
The generation of gravitational waves by neutron stars follows the same scenario as when merging black holes, only the waves generated by neutron stars are weaker. While revolving around a common center of gravity in a binary system, two neutron stars lose energy by emitting gravitational waves. Therefore, they gradually approach each other until they merge into one neutron star (there is a possibility that a black hole may also appear during the merger). The merger of two neutron stars is accompanied by an outburst that is much brighter than an ordinary nova. Astronomers suggest the name "kilonova" for it. Part of the mass of two stars during the merger is converted into the energy of gravitational waves, which were noticed this time by earth scientists.
Although kilonova stars were predicted more than 30 years ago, this is the first time such a star has been discovered. Its characteristics, determined as a result of observations, are in good agreement with earlier predictions. As a result of the merger of two neutron stars and the explosion of a kilonova, radioactive heavy chemical elements are released, scattering at a speed of one-fifth the speed of light. Within a few days - faster than any other stellar explosion - the kilonova's color changes from bright blue to red. “When the spectrum of the object appeared on our monitors, I realized that this is the most unusual transient phenomenon I have ever seen,” says Stephen Smartt, who made observations with ESO NTT. - I've never seen anything like it. Our data, as well as the data of other research groups, clearly show that it was not a supernova or a variable background star, but something completely unusual. "
The star's emission spectra show the presence of cesium and tellurium, ejected into space by merging neutron stars. This observation confirmed the theory of r-nucleosynthesis (r-process, a fast process of neutron capture) formulated earlier by astrophysicists in the interiors of superdense stellar objects. The chemical elements formed during the merger of neutron stars, after the explosion of the kilonova, scattered in space.
Another theory of astronomers has also been confirmed, according to which short gamma-ray bursts occur when neutron stars merge. This idea was expressed for a long time, but only the combination of data from the gravitational observatories LIGO and Virgo with the observations of astronomers made it possible to finally make sure that it was correct.
“So far, the data we have obtained are in excellent agreement with theory. This is a triumph of theorists, confirmation of the absolute reality of the events recorded by the LIGO – VIRGO devices, and a remarkable achievement of ESO, which managed to obtain such observations of a kilonova ”, - says astronomer Stefano Covino (Stefano Covino).
Before we observed this event, we had two ways to estimate the frequency of neutron hole mergers: measurements of binary neutron stars in our galaxy (as from pulsars) and our theoretical models of the formation of stars, supernovae and their remnants. All this gives us an estimate - about 100 such mergers occur annually within a cubic gigaparsec of space.
The observation of the new event provided us with the first observable estimate of the auroral frequency, and it is ten times higher than expected. We thought we'd need a LIGO that had reached the limit of sensitivity (it's halfway there now) to see at least something, and then three additional detectors to pinpoint the exact location. And we managed not only to see it early, but also to localize it on the first try. So, the question is: were we just lucky to see this event, or is the frequency of those really much higher than we thought? If higher, in what then are our theoretical models wrong? Next year, LIGO will be spent on modernization, and theorists will have a little time to brainwash.
What causes the substance to be thrown out in the fusion process in such an amount?
Our best theoretical models predicted that star mergers like this would be accompanied by a bright light signal in the ultraviolet and optical parts of the spectrum during the day, and then fade and disappear. But instead, the aurora lasted two days before it began to fade, and of course we had questions. The bright glow, which lasted so long, indicates that the winds in the disk around the stars ejected 30-40 Jupiter masses in the form of matter. According to our data, the substance should have been less than half or even eight times.
What is so unusual about these emissions? To simulate such a merge, you need to include many different physics:
- hydrodynamics
- magnetic fields
- equation of state of matter at nuclear densities
- interactions with neutrinos
…and much more. Different codes model these components with different levels of difficulty, and we don't know for sure which component is responsible for these winds and emissions. Finding the right one is a problem for theorists, and we have to put up with the fact that we measured the merger of neutron stars for the first time ... and got a surprise.
In the final moments of the merger, the two neutron stars not only emit, but also a catastrophic explosion that echoes across the entire electromagnetic spectrum. And if the product is a neutron star, a black hole, or something exotic in between, the transition state is still unknown to us.
Did this merger produce a supermassive neutron star?
To obtain enough mass lost from a merger of neutron stars, the product of that merger must generate enough energy of the appropriate type to blow this mass off the disk surrounding the star. Based on the observed gravitational-wave signal, we can say that this merger created an object with a mass of 2.74 solar masses, which is well above the maximum solar mass that a non-rotating neutron star can have. That is, if nuclear matter behaves as expected, the merger of two neutron stars should have led to the appearance of a black hole.
A neutron star is one of the densest collections of matter in the universe, but its mass has an upper limit. Exceed it and the neutron star will collapse again to form a black hole.
If the core of this object, after the merger, immediately collapsed into a black hole, there would be no ejection. If instead it were to become a supermassive neutron star, it would have to rotate extremely fast, since the large angular momentum would increase the maximum mass limit by 10-15%. The problem is that if we were to get a supermassive neutron star spinning so rapidly, it would have to become a magnetar with an extremely powerful magnetic field, a quadrillion times more powerful than the fields on the Earth's surface. But magnetars quickly stop spinning and should collapse into a black hole in 50 milliseconds; our observations of magnetic fields, viscosity, and heating that ejected the mass show that the object has existed for hundreds of milliseconds.
Something is wrong here. Either we have a rapidly rotating neutron star, which for some reason is not a magnetar, or we will have ejections for hundreds of milliseconds, and our physics does not give us an answer. At the same time, even for a short time, most likely, we had a supermassive neutron star, and behind it a black hole. If both options are correct, we are dealing with the most massive neutron star and the smallest black hole ever!
If these neutron stars were more massive, would the merger be invisible?
There is a limit to how massive neutron stars can be, and if you add and add masses, you end up with a black hole. This limit of 2.5 solar masses for non-rotating neutron stars means that if the total mass of the merger is lower, you will almost certainly be left with the neutron star after the merger, resulting in the strong and long lasting ultraviolet and optical signals that we saw in this case. On the other hand, if you rise above 2.9 solar masses, a black hole will form immediately after the merger, quite possibly - without ultraviolet and optical accompaniments.
One way or another, our very first merger of neutron stars was exactly in the middle of this range, when a supermassive neutron star could appear, creating ejections and optical and ultraviolet signals for a short time. Do magnetars form in less massive mergers? And the more massive ones - they immediately come to black holes and remain invisible at these wavelengths? How rare or widespread are these three categories of mergers: ordinary neutron stars, supermassive neutron stars, and black holes? In a year, LIGO and Virgo will be looking for answers to these questions, and theorists will have just a year to bring their models in line with predictions.
What causes gamma ray bursts to be so bright in many directions and not in a cone?
This question is very difficult. On the one hand, the discovery confirmed what had long been suspected, but could not prove in any way: that merging neutron stars do indeed produce gamma ray bursts. But we have always assumed that gamma ray bursts only emit gamma rays in a narrow, conical shape, 10-15 degrees in diameter. Now we know, from the merging position and the magnitude of the gravitational waves, that gamma ray bursts are going 30 degrees from our line of sight, but we are seeing a powerful gamma ray signal.
The nature of gamma ray bursts must change. The challenge for theorists is to explain why the physics of these objects is so different from that predicted by our models.
On a separate line: how opaque / transparent are heavy elements?
When it comes to the heaviest elements in the periodic table, we know that they are mostly produced not by supernovae, but by mergers of black holes. But to get the spectra of heavy elements from a distance of 100 million light years, you need to understand their transparency. This includes understanding the atomic physical transitions of electrons in orbitals of an atom in an astronomical setting. For the first time, we have an environment for testing how astronomy intersects with atomic physics, and subsequent observations of mergers should allow us to answer the question of opacity and transparency as well.
It is possible that neutron stars are constantly merging, and when LIGO reaches the planned sensitivity level, we will find dozens of mergers a year. It is also possible that this event was extremely rare and we are lucky to see only one per year even after updating installations. Theoretical physicists will spend the next ten years looking for answers to the above questions.
The future of astronomy lies before us. Gravitational waves are a completely independent way of exploring the sky, and by comparing the sky with gravitational waves with traditional astronomical charts, we are ready to answer questions that we did not dare to ask a week ago.
Today, at a press conference in Washington, scientists officially announced the registration of an astronomical event that no one has recorded before - the merger of two neutron stars. According to the results of the observation, more than 30 scientific articles were published in five journals, so we cannot tell about everything at once. Here is a rundown and the most important discoveries.
Astronomers have observed the merger of two neutron stars and the birth of a new black hole.
Neutron stars are objects that appear as a result of explosions of large and massive (several times heavier than the Sun) stars. Their dimensions are small (they are usually no more than 20 kilometers in diameter), but their density and mass are enormous.
As a result of the merger of two neutron stars 130 million light-years from Earth, a black hole was formed - an object even more massive and dense than a neutron star. The merging of stars and the formation of a black hole was accompanied by the release of enormous energy in the form of gravitational, gamma and optical radiation. All three types of radiation were recorded by terrestrial and orbiting telescopes. The gravitational wave was recorded by the LIGO and VIRGO observatories.
This gravitational wave was the highest energy wave ever observed.
All forms of radiation reached Earth on August 17. First, ground-based laser interferometers LIGO and Virgo recorded periodic compression and expansion of space-time - a gravitational wave that circled the globe several times. The event that generated the gravitational wave was named GRB170817A. Seconds later, NASA's Fermi gamma-ray telescope detected high-energy photons in the gamma range.
On this day, large and small, ground-based and orbiting telescopes operating in all ranges were looking at one point in space.
Based on the results of observations at the University of California (Berkeley), a computer simulation of the merger of neutron stars was made. Both stars were, most likely, a little more than the mass of the Sun (but much smaller in radius). These two balls of incredible density swirled around each other, constantly accelerating. This is how it was:
As a result of the merger of neutron stars, atoms of heavy elements - gold, uranium, platinum - got into outer space; astronomers believe that such events are the main source of these elements in the universe. Optical telescopes first "saw" blue visible light, and then ultraviolet radiation, which was replaced by red light and radiation in the infrared range.
This sequence is consistent with theoretical predictions. According to the theory, colliding, neutron stars lose part of the matter - it is sprayed around the collision site with a huge cloud of neutrons and protons. When a black hole begins to form, an accretion disk forms around it, in which particles rotate at a tremendous speed - so enormous that some overcome the black hole's gravity and fly away.
Such a fate awaits about 2% of the matter of colliding stars. This substance forms a cloud around the black hole with a diameter of tens of thousands of kilometers and a density approximately equal to that of the Sun. The protons and neutrons that make up this cloud stick together to form atomic nuclei. Then the decay of these nuclei begins. The radiation of decaying nuclei was observed by terrestrial astronomers for several days. Over the millions of years that have passed since the GRB170817A event, this radiation has filled the entire galaxy.
For the first time in human history, astronomers have recorded gravitational waves from the merger of two neutron stars. The event in the galaxy NGC 4993 was "smelled" on August 17 by the LIGO / Virgo gravitational observatories. Following them, other astronomical instruments joined in the observations. As a result, 70 observatories watched the event, and according to the observations, at least 20 (!) Scientific articles have been published today.
Rumors that the LIGO / Virgo detectors have finally registered a new event and this is not another merger of black holes, spread on social networks on August 18. Statements about him were expected at the end of September, but then scientists limited themselves to just another gravitational-wave event involving two black holes - it happened 1.8 billion light years from Earth, and not only American detectors took part in its observation on August 14 for the first time, but also the European Virgo, which "joined" in the hunt for space-time fluctuations two weeks before.
New LIGO. Source with optical counterpart. Blow your sox off!
J Craig Wheeler (@ ast309) August 18, 2017
After that, the collaboration its well-deserved Nobel Prize in physics - for the detection of gravitational waves and confirmation of the correctness of Einstein, who predicted their existence - and now it told the world about the discovery, which it saved for "sweet".
What exactly happened?
Neutron stars are very, very small and very dense objects that usually arise from supernova explosions. The typical diameter of such a star is 10-20 km, and the mass is comparable to the mass of the Sun (the diameter of which is 100,000,000 times larger), so that the density of matter in a neutron star is several times higher than the density of an atomic nucleus. At the moment, we know of several thousand such objects, but there are only one and a half to two dozen binary systems.
Kylon (by analogy with the "supernova"), the gravitational effect of which was registered by LIGO / Virgo on August 17, is located in the constellation Hydra at a distance of 130 million light years from Earth. It arose from the merger of two neutron stars with masses ranging from 1.1 to 1.6 solar masses. How close this event was to us is indicated by the fact that while the signal from merging binary black holes was usually in the sensitivity range of the LIGO detectors for a fraction of a second, the signal recorded on August 17 lasted for about 100 seconds.
“This is not the first kilonova recorded,” astrophysicist Sergei Popov, a leading researcher at the State Astronomical Institute named after V.I. PC. Sternberg, - but they could be listed not even on the fingers of one hand, but almost on the ears. There were literally one or two of them. "
At almost the same time, about two seconds after the gravitational waves, NASA's Fermi Space Telescope and the INTErnational Gamma-Ray Astrophysics Laboratory / INTEGRAL recorded gamma ray bursts. In the days that followed, scientists recorded electromagnetic radiation in other ranges, including X-rays, ultraviolet, optical, infrared and radio waves.
Having received the coordinates, several observatories were able to start searching in the region of the sky where the event supposedly occurred within a few hours. A new bright point, reminiscent of a new star, was detected by optical telescopes, and as a result, about 70 observatories observed this event at various wavelengths.
“For the first time, unlike the 'lonely' mergers of black holes, a 'companionable' event was registered not only by gravitational detectors, but also by optical and neutrino telescopes. This is the first such round dance of observations around one event, ”said Sergei Vyatchanin, professor of the physics department of Moscow State University, who is part of a group of Russian scientists who participated in the observation of the phenomenon under the leadership of professor of the physics department of Moscow State University Valery Mitrofanov.
At the time of the collision, the bulk of the two neutron stars merged into one ultra-dense object emitting gamma rays. The first measurements of gamma rays, combined with the detection of gravitational waves, support the prediction of Einstein's general theory of relativity, namely that gravitational waves travel at the speed of light.
“In all previous cases, merging black holes were the source of gravitational waves. Paradoxically, black holes are very simple objects consisting solely of curved space and therefore fully described by the well-known laws of general relativity. At the same time, the structure of neutron stars and, in particular, the equation of state of neutron matter are still not known exactly. Therefore, the study of signals from merging neutron stars will provide a huge amount of new information about the properties of superdense matter in extreme conditions, ”said Professor of the Physics Department of Moscow State University Farit Khalili, who is also part of Mitrofanov's group.
What is the significance of this discovery?
First, observing neutron star mergers is another clear demonstration of the effectiveness of astronomical observations, pioneered by the LIGO and Virgo detectors.
“This is the birth of a new science! Such is the day today, - Vladimir Lipunov, head of the space monitoring laboratory of the Moscow State University and the head of the MASTER project, told Cherdak. - It will be called gravitational astronomy. This is when all the thousand-year-old methods of astronomy, which thousands of astronomers have applied for many thousands of years, have worked out, will become useful for gravitational-wave topics. Until now, all this was pure physics, that is, even fantasy from the point of view of the public, but now it is already reality. New Reality ".
“A year and a half ago, when gravitational waves were discovered, a new way of studying the Universe was discovered, studying the nature of the Universe. And this new method has already demonstrated its ability to give us important, deep information about various phenomena in the Universe in a year and a half. For several decades, gravitational waves were only trying to detect, and then once - a year and a half ago they were detected, they received the Nobel Prize, and now a year and a half have passed, and it has indeed been shown that apart from the flag that everyone was raising - aha, Einstein was right! - it is really working already now, only at the beginning of the science of gravitational astronomy, it turns out to be so effective as to study various phenomena in the Universe, ”astrophysicist Yuri Kovalev, head of the laboratory for fundamental and applied research of relativistic objects of the Universe at MIPT, head of the laboratory, told the Attic correspondent FIAN, head of the scientific program of the Radioastron project.
In addition, a huge amount of new data was collected during the observations. In particular, it was recorded that in the process of merging neutron stars, heavy elements such as gold, platinum and uranium are formed. This confirms one of the existing theories of the origin of heavy elements in the Universe. Simulations have already shown that supernova explosions alone are not enough for the synthesis of heavy elements in the Universe, and in 1999 a group of Swiss scientists suggested that mergers of neutron stars could serve as another source of heavy elements. Although kilonovae are much rarer than supernova explosions, they can generate most of the heavy elements.
“Imagine, you've never found money on the street, and then you finally found it. And this is just a thousand dollars, - says Sergei Popov. - Firstly, it is a confirmation that gravitational waves propagate with the speed of light, a confirmation with an accuracy of 10 -15. This is a very important thing. Secondly, this is a certain number of purely technical confirmations of a number of provisions of the general theory of relativity, which is very important for fundamental physics in general. Thirdly - if we go back to astrophysics - this is confirmation that short GRBs are mergers of neutron stars. And as for the heavy elements, then, of course, not that no one believed in such things before. But there was no such gorgeous data set. "
And this set of data already on the first day allowed scientists to publish, according to the calculations of "Attic", at least 20 articles (eight in Science, five in Nature, two in Physical Review Letters and five in Astrophysical Journal Letters). According to the calculations of journalists Science, the number of authors of the article describing the event corresponds to about a third of all active astronomers. Are you looking forward to continuing? We are.
Immediately in all ranges of the spectrum plus - register gravitational waves from this event. The photograph taken by the Hubble telescope shows the galaxy NGC 4993 in which this happened. The yellow spot above and to the left of the center of the galaxy is a merger flash. The sidebars show how it changed from 22 to 28 August.
The gravitational wave burst itself occurred on August 17 this year, and therefore received the name GW170817. At the beginning, he was caught on VIRGO (the installation successfully connected for a short time to the scientific observation session of LIGO), and then - after a split second - on American detectors. The observed splash lasted almost two minutes! It's worth listening to!
But most importantly, after 1.7 seconds, gamma detectors on the Fermi and INTEGRAL satellites recorded a short gamma-ray burst, named GRB 170817A. As it quickly became clear, these are related events.
Gravitational detectors cannot very accurately determine the burst point in the sky, even in this case, when three detectors were triggered, the area of \u200b\u200buncertainty was about 30 square degrees (more than 100 lunar disks), but gamma detectors can determine the coordinates much more accurately. Therefore, it was immediately possible to connect observers working in the entire spectrum range (in addition, the data from neutrino detectors were analyzed, but they did not see anything, as, incidentally, was expected). And this led to an amazing discovery - the burst and its afterglow were seen in X-ray, optical, ultraviolet and infrared ranges!
Since the gravitational wave signal and the gamma-ray burst arrived almost simultaneously, it is possible to assert with high accuracy (approximately 10-15) that the propagation speed of gravitational waves is equal to the speed of light (note that the delay is most likely associated not with the difference in velocities, but with the physics of generation gamma-ray burst). In addition, it was possible, with a higher accuracy than before, to verify several more predictions of the General Theory of Relativity.
The presence of a gravitational wave signal allows you to directly determine the distance to the merging objects. And the data of optical measurements give the identification of the galaxy, that is, they allow to determine the redshift. Together, these independent measurements provide the Hubble constant. So far, however, they are not very accurate - 60–80 (km / s) / Mpc. This accuracy is worse than in a number of other cosmological measurements. However, it is important that in this case the Hubble constant is measured by a completely different independent method, moreover, by a model-independent method (that is, there is no need to lay additional theoretical assumptions to obtain a result). Therefore, we can hope that in the future such data on the observation of mergers of neutron stars using gravitational-wave detectors in galaxies with a known redshift will become a source of significant cosmological information.
So. At a distance of 130 million light years (40 megaparsecs), two neutron stars merged in the galaxy NGC 4993. As a result, a gravitational wave burst occurred, and a large amount of energy was released in different ranges of the electromagnetic spectrum.
In addition to the main flare, for some time astronomers also observed the so-called kilonova (they are sometimes also called macron, see Kilonova). This radiation is associated with the decay of radioactive elements synthesized as a result of the merger of neutron stars. The synthesis takes place as a result of the so-called r-process, the letter "r" here is from the word rapid (fast). After the fusion, the expanding substance is permeated by a flux of neutrons and neutrinos. This creates favorable conditions for the transformation of the nuclei of elements into heavier ones. Nuclei capture neutrons, which can then turn into protons inside the nucleus, as a result of which the nucleus jumps one cell in the periodic table. So you can "jump" not only to lead, but also to uranium and thorium. Modern calculations show that the bulk of heavy elements (with a mass of more than 140), for example, gold and platinum, are synthesized precisely as a result of the merger of neutron stars, and not in the process of supernova explosions.
Thus, a large set of data was obtained from one event, which is interesting for various fields of physics and astrophysics:
1. The connection of short gamma-ray bursts with mergers of neutron stars has been proved. New data will provide a much better understanding of the physics of short GRBs.
2. It was possible to carry out an excellent check of a number of predictions of general relativity (speed of propagation of gravitational waves, Lorentz invariance, the principle of equivalence).
3. Unique data were obtained on the synthesis of elements during the merger of neutron stars.
4. It was possible to obtain a direct measurement of the Hubble constant
We expect that subsequent observations will help to determine the masses and radii of neutron stars with high accuracy (which is important for understanding their structure, that is, it is relevant for nuclear physics as well), and we are also waiting for an event where the merger of two neutron stars will lead to the observed formation of a black hole. By the way, it is impossible to say exactly what happened as a result of this event (but most likely, a black hole was formed after all).
In conclusion, we note that astronomers are very, very lucky. First, the surge is very close. Second, the likelihood that a gravitational wave burst will be accompanied by a gamma-ray burst is not very high. Let's hope that astronomers will continue to be lucky!
The original articles with materials related to the discovery can be found on the LIGO website.
Sergey Popov