Gravitational waves neutron stars. GW170817, or Astronomically important hundred seconds of summer. For the first time in history, gravitational waves from the merger of neutron stars have been detected. What is the Hubble constant?

For the first time in human history, astronomers have detected gravitational waves from the merger of two neutron stars. The event in the galaxy NGC 4993 was “sensed” on August 17 by the LIGO/Virgo gravitational observatories. Following them, other astronomical instruments joined in the observations. As a result, 70 observatories observed the event, and according to observational data, at least 20 (!) scientific articles were published today.

Rumors that the LIGO/Virgo detectors have finally registered a new event and this is not another black hole merger began to spread across social networks on August 18. A statement about it was expected at the end of September, but then scientists limited themselves to only the next gravitational wave event involving two black holes - it occurred 1.8 billion light years from Earth, and for the first time not only American detectors took part in its observation on August 14, but also the European Virgo, which “joined” the hunt for space-time fluctuations two weeks earlier.

New LIGO. Source with optical counterpart. Blow your sox off!

J Craig Wheeler (@ast309) August 18, 2017

After this, the collaboration won its well-deserved Nobel Prize in physics - for the detection of gravitational waves and confirmation of Einstein’s correctness in predicting their existence - and now it has told the world about the discovery that it saved for “sweets”.

What exactly happened?

Neutron stars are very, very small and very dense objects that are usually created by supernova explosions. The typical diameter of such a star is 10-20 km, and the mass is comparable to the mass of the Sun (whose diameter is 100,000,000 times larger), so the density of the neutron star’s substance is several times higher than the density of the 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.

A kilonova (similar to a “supernova”), the gravitational effect of which was recorded by LIGO/Virgo on August 17, is located in the constellation Hydra at a distance of 130 million light years from Earth. It resulted from the merger of two neutron stars with masses ranging from 1.1 to 1.6 solar masses. An indication of how close this event was to us is that while the signal from merging binary black holes was typically within the sensitivity range of LIGO detectors for a fraction of a second, the signal recorded on August 17 lasted about 100 seconds.

“This is not the first registered kilonova,” said astrophysicist Sergei Popov, leading researcher at the State Astronomical Institute. 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.”

Almost at the same time, about two seconds after the gravitational waves, NASA's Fermi Gamma-ray Space Telescope and INTERnational Gamma-Ray Astrophysics Laboratory/INTEGRAL detected gamma-ray bursts. In the following days, scientists recorded electromagnetic radiation in other ranges, including X-ray, ultraviolet, optical, infrared and radio waves.

Having received the coordinates, several observatories were able to begin searching within a few hours in the area of ​​​​the sky where the event supposedly occurred. The new bright point, resembling a nova, was detected by optical telescopes, and about 70 observatories eventually observed the event in various wavelength ranges.

“For the first time, in contrast to “lonely” black hole mergers, a “company” event was recorded 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 Professor of the Faculty of Physics of Moscow State University Sergei Vyatchanin, who is part of a group of Russian scientists who participated in the observation of the phenomenon under the leadership of Professor of the Faculty of Physics of Moscow State University Valery Mitrofanov.

At the moment of the collision, the main part 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, confirm the prediction of Einstein's general theory of relativity, namely that gravitational waves travel at the speed of light.

“In all previous cases, the source of gravitational waves was merging black holes. Paradoxically, black holes are very simple objects, consisting entirely of curved space and therefore completely 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 is still precisely unknown. Therefore, studying signals from merging neutron stars will allow us to obtain a huge amount of new information also about the properties of superdense matter in extreme conditions,” said Farit Khalili, a professor at the Faculty of Physics at Moscow State University, 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 power of astronomical observations pioneered by the LIGO and Virgo detectors.

“This is the birth of a new science! Today is such a day,” Vladimir Lipunov, head of the space monitoring laboratory of the State Aviation Institute of Moscow State University and 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 used for many thousands of years, have developed, will become useful for gravitational wave topics. Until today, all this was pure physics, that is, even fantasy from the point of view of the public, but now it is already a reality. New reality."

“A year and a half ago, when gravitational waves were discovered, a new way of studying the Universe, studying the nature of the Universe was discovered. And this new method has already demonstrated in a year and a half its ability to give us important, deep information about various phenomena in the Universe. For several decades, they were just trying to detect gravitational waves, and then once - a year and a half ago they were detected, received the Nobel Prize, and now a year and a half has passed, and it has really been shown that, except for the flag that everyone raised - yeah, Einstein was right! “It’s really working now, only at the beginning of the science of gravitational astronomy, it turns out to be so effective 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 Lebedev Physical Institute, head of the scientific program of the Radioastron project.

In addition, during the observations a huge amount of new data was collected. In particular, it was recorded that during the merger of 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. Previous modeling had already demonstrated that supernova explosions alone are not enough to synthesize heavy elements in the Universe, and in 1999 a group of Swiss scientists suggested that neutron star mergers could be another source of heavy elements. Although kilonovae are much rarer than supernovae, 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 a thousand dollars at once,” says Sergei Popov. - Firstly, this is confirmation that gravitational waves propagate at the speed of light, 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 return to astrophysics - this is confirmation that short gamma-ray bursts are the merger of neutron stars. As for heavy elements, of course, it’s not that no one believed in such things before. But there wasn’t such a gorgeous set of data.”

And this complex of data already on the first day allowed scientists to publish, according to Attic calculations, at least 20 articles (eight in Science, five in Nature, two in Physical Review Letters and five in Astrophysical Journal Letters). According to journalists' estimates Science, the number of authors of the article describing the event roughly corresponds to a third of all active astronomers. Are you looking forward to the continuation? We do.

Russian scientists as part of the LIGO and Virgo collaborations have for the first time detected gravitational waves from the merger of two neutron stars. This is the first cosmic event observed in both gravitational and electromagnetic waves. The discovery was presented today at press conferences in Washington and Moscow. The results will also be published in the journal Physical Review Letters.

Two weeks after the Nobel Prize in Physics was awarded to three US researchers for the discovery of gravitational waves, the LIGO (Laser Interferometric Gravitational Wave Observatory, US) and Virgo (a similar observatory in Italy) collaboration announced that they had detected for the first time gravitational waves from the merger of two neutrons. stars, and this phenomenon was observed on laser interferometers that record gravitational waves, using space observatories (Integral, Fermi) and ground-based telescopes that record electromagnetic radiation. In total, this phenomenon was observed by about 70 ground-based and space observatories around the world, including the MASTER network of robotic telescopes (M.V. Lomonosov Moscow State University).

“The first direct detection of gravitational waves from colliding black holes by the LIGO observatory took place about two years ago. A new window to the Universe was opened. Already today we see what unprecedented opportunities this new channel for obtaining information in combination with traditional astronomy creates for researchers,” says Valery Mitrofanov, professor at the Faculty of Physics at Moscow State University.

On August 17, both LIGO detectors detected a gravitational signal called GW170817. The information provided by the third Virgo detector has significantly improved the localization of the cosmic event. Almost at the same time (about two seconds after the gravitational waves), NASA's Fermi Gamma-Ray Space Telescope and the INTEGRAL International Gamma-Ray Astrophysics Laboratory (INTEGRAL) detected gamma-ray bursts. In the following days, electromagnetic radiation was recorded in other ranges, including X-ray, ultraviolet, optical, infrared and radio waves.

Signals from the LIGO detectors showed that the detected gravitational waves were emitted by two astrophysical objects rotating relative to each other and located at a relatively close distance, about 130 million light years, from Earth. It turned out that the objects were less massive than the binary black holes previously discovered by LIGO and Virgo. Their masses were calculated to be between 1.1 and 1.6 solar masses, which falls within the mass range of neutron stars, the smallest and densest stars. Their typical radius is only 10-20 kilometers.

Having received the coordinates, within a few hours the observatories were able to begin searching the area of ​​the sky where the event supposedly occurred. A new bright point resembling a nova was discovered by optical telescopes. Ultimately, about 70 observatories on Earth and in space observed the event in various wavelength ranges. In the days following the collision, electromagnetic radiation was recorded in the X-ray, ultraviolet, optical, infrared and radio wave ranges.

“For the first time, in contrast to “lonely” black hole mergers, a “company” event was recorded 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 a professor at the Faculty of Physics of Moscow State University named after M.V. Lomonosov Sergey Vyatchanin.

Theorists predicted that the merger would produce a "kilonova." This is a phenomenon in which material left over from a neutron star collision glows brightly and is ejected from the collision area far into space. This creates processes that create heavy elements such as lead and gold. Observing the afterglow of a neutron star merger provides additional information about the various stages of the merger, the interaction of the resulting object with its environment, and the processes that produce the heaviest elements in the Universe.

“During the fusion process, the formation of heavy elements was recorded. Therefore, we can even talk about a galactic factory for the production of heavy elements, including gold, because it is this metal that interests earthlings most of all. Scientists are beginning to propose models that would explain the observed parameters of this merger,” Vyatchanin noted.

Illustration copyright Getty Images Image caption The phenomenon was observed using space observatories and ground-based telescopes

Scientists have been able to detect gravitational waves from the merger of two neutron stars for the first time.

The waves were recorded by LIGO detectors in the USA and the Italian Virgo Observatory.

According to researchers, as a result of such mergers, elements such as platinum and gold appear in the Universe.

The discovery was made on August 17th. Two detectors in the United States detected the gravitational signal GW170817.

Data from the third detector in Italy made it possible to clarify the localization of the cosmic event.

“This is what we've all been waiting for,” said LIGO Laboratory Executive Director David Reitze, commenting on the discovery.

The merger occurred in the galaxy NGC4993, which is located about 130 million light years from Earth in the constellation Hydra.

The star masses ranged from 1.1 to 1.6 solar masses, which falls within the mass range of neutron stars. Their radius is 10-20 km.

Stars are called neutron stars because, during the process of gravitational compression, protons and electrons inside the star merge, resulting in an object consisting almost exclusively of neutrons.

Such objects have incredible density - a teaspoon of matter would weigh about a billion tons.

The LIGO laboratory in Livingston, Louisiana, is a small building from which two pipes extend at right angles - the arms of the interferometer. Inside each of them there is a laser beam, recording changes in the length of which gravitational waves can be detected.

The LIGO detector, set in the middle of vast forests, was designed to detect gravitational waves that generate large-scale cosmic cataclysms such as neutron star mergers.

The detector was upgraded four years ago, and since then it has detected black hole collisions four times.

Gravitational waves, which arise as a result of large-scale events in space, lead to the emergence of time-spatial distortions, somewhat similar to ripples in water.

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They stretch and compress all the matter they pass through to an almost insignificant degree - less than the width of one atom.

“I’m delighted with what we’ve done. I first started working on gravitational waves in Glasgow while I was still a student. Many years have passed since then, there have been ups and downs, but now everything has come together,” says LIGO worker, Professor Norna Robertson.

“Over the past few years, we have first detected the merger of black holes and then neutron stars, and I feel like we are opening up a new field for research,” she adds.

• The existence of gravitational waves was predicted by Einstein's general theory of relativity
• It took decades to develop the technology that made it possible to record the waves.
• Gravitational waves are distortions in time and space that arise as a result of large-scale events in space
• Rapidly accelerating matter generates gravitational waves that travel at the speed of light
• Among the visible sources of waves are mergers of neutron stars and “black holes.”
• Wave research opens up a fundamentally new field for research

Scientists believed that the release of energy on such a scale led to the creation of rare elements such as gold and platinum.

According to Dr Kate Maguire from Queen's University Belfast, who analyzed the first outbreaks that arose from the merger, this theory has now been proven.

"Using the world's most powerful telescopes, we discovered that this neutron star merger produced a high-velocity release of heavy chemical elements such as gold and platinum into space," says Maguire.

"These new results make significant progress toward resolving a long-standing dispute about where elements heavier than iron come from on the periodic table," she adds.

New frontiers

Observations of the neutron star collision also confirmed the theory that it is accompanied by short bursts of gamma rays.

By combining the information collected about the gravitational waves resulting from the collision with data on light radiation collected using telescopes, scientists used a previously unused method to measure the rate of expansion of the Universe.

One of the most influential theoretical physicists on the planet, Professor Stephen Hawking, speaking to the BBC, called it "the first rung on the ladder" to a new way of measuring distances in the Universe.

"New ways of observing the universe tend to lead to surprises, many of which cannot be foreseen. We are still rubbing our eyes, or rather, clearing our ears, after hearing the sound of gravitational waves for the first time," Hawking said.

Now the equipment of the LIGO complex is being modernized. In a year, it will become twice as sensitive, and will be able to scan a section of space that is eight times larger than it is now.

Scientists believe that in the future, observations of collisions between black holes and neutron stars will become commonplace. They also hope to be able to observe objects that they cannot even imagine today, and begin a new era in astronomy.

On August 17, 2017, the laser interferometer gravitational-wave observatory LIGO and the French-Italian gravitational wave detector VIRGO recorded gravitational waves from the collision of two neutron stars for the first time. About two seconds later, NASA's Fermi Gamma-ray Space Telescope and ESA's INTEGRAL Gamma-ray Astrophysics Laboratory observed a short gamma-ray burst, GRB170817A, in the same area of ​​the sky.

“It is rare for a scientist to have the opportunity to witness the beginning of a new era in science. This is one of those cases!” - said Elena Pian from the Astrophysical Institute of Italy, author of one of the publications in Nature articles.

What are gravitational waves?

Gravitational waves, created by moving masses, are markers of the most violent events in the Universe and occur when dense objects such as black holes or neutron stars collide.

Their existence was predicted back in 1916 by Albert Einstein in his General Theory of Relativity. However, it was possible to detect gravitational waves only after a hundred years, since only the most powerful of these waves, caused by rapid changes in the speed of very massive objects, can be recorded by modern receivers.

Until today, 4 signals of gravitational waves have been caught: three times LIGO alone recorded the “ripples” of space-time, and on September 14, 2017, for the first time, gravitational waves were caught by three detectors at once (two LIGO detectors in the USA and one VIRGO detector in Europe).

The four previous events have one thing in common - they are all caused by the merger of pairs of black holes, as a result of which it is impossible to see their source. Now everything has changed.

How observatories around the world “caught” the source of gravitational waves

The joint work of LIGO and VIRGO made it possible to position the source of gravitational waves within a vast area of ​​the southern sky, the size of several hundred disks of the full Moon, containing millions of stars. More than 70 observatories around the world, as well as NASA's Hubble Space Telescope, began observing this region of the sky in search of new sources of radiation.

The first message about the discovery of a new light source came 11 hours later from the Swope meter telescope. It turned out that the object was very close to the lenticular galaxy NGC 4993 in the constellation Hydra. Almost at the same time, the same source was detected by ESO's VISTA telescope in infrared light. As the night moved west across the globe, the object was observed in the Hawaiian Islands by the Pan-STARRS and Subaru telescopes, and its rapid evolution was noted.

The flash from the collision of two neutron stars in the galaxy NGC 4993 is clearly visible in this image from the Hubble Space Telescope. Observations carried out from August 22 to 28, 2017 show how it gradually disappeared. Credit: NASA/ESA

Estimates of the object's distance from both gravitational wave data and other observations have yielded consistent results: GW170817 is at the same distance from Earth as the galaxy NGC 4993, 130 million light-years away. This makes it the closest gravitational wave source ever discovered to us, and one of the closest gamma-ray burst sources ever observed.

Mysterious kilonova

After a massive star explodes as a supernova, it is left behind with a super-dense, collapsed core: a neutron star. Neutron star mergers also largely explain short gamma-ray bursts. This event is believed to be accompanied by an explosion a thousand times brighter than a typical nova - a so-called kilonova.

An artist's representation of the collision of two neutron stars in the galaxy NGC 4993, producing a kilonova flare and gravitational waves. Credit: ESO/L. Calgada/M. Kornmesser

“This is like nothing else! The object very quickly became incredibly bright, and then began to rapidly fade, turning from blue to red. This is incredible! " – says Ryan Foley from the University of California at Santa Cruz (USA).

The almost simultaneous detection of gravitational waves and gamma rays from GW170817 raised hopes that this was the long-sought kilonova. Detailed observations using ESO's instruments and the Hubble Space Telescope have indeed revealed properties of this object very close to theoretical predictions made more than 30 years ago. Thus, the first observational confirmation of the existence of kilonovae was obtained.

It is not yet clear what kind of object was created by the merger of two neutron stars: a black hole or a new neutron star. Further data analysis should answer this question.

The merger of two neutron stars and the explosion of a kilonova releases radioactive heavy chemical elements, flying away at one-fifth the speed of light. Over the course of a few days—faster than any other stellar explosion—the kilonova's color changes from bright blue to very red.

“The data we obtained is in excellent agreement with the theory. This is a triumph for theorists, a confirmation of the absolute reality of the events recorded by the LIGO and VIRGO installations, and a remarkable achievement by ESO, which managed to obtain observations of the kilonova,” says Stefano Covino from the Astrophysical Institute of Italy, the author of one of the papers published in Nature Astronomy articles.

Some of the elements ejected into space when two neutron stars merge. Credit: ESO/L. Calçada/M. Kornmesser

Spectra obtained by instruments on ESO's Very Large Telescope reveal the presence of cesium and tellurium ejected into space by neutron star mergers. These and other heavy elements are dispersed into space after kilonova explosions. Thus, observations indicate the formation of elements heavier than iron during nuclear reactions in the interior of superdense stellar objects. This process, called r-nucleosynthesis, was previously known only in theory.

The importance of discovery

The discovery marked the dawn of a new era in cosmology: now we can not only listen, but also see the events that generate gravitational waves! In the short term, analysis of the new data will allow scientists to gain a more accurate understanding of neutron stars, and in the future, observations of similar events will help explain the ongoing expansion of the Universe, the composition of dark energy, and the origin of the heaviest elements in the cosmos.

Research describing the discovery is presented in a series of journal articles Nature, Nature Astronomy And Astrophysical Journal Letters.

Observational results may in the future shed light on the mystery of the structure of neutron stars and the formation of heavy elements in the Universe

Artist's depiction of gravitational waves generated by the merger of two neutron stars

Image: R. Hurt/Caltech-JPL

Moscow. October 16. website - For the first time in history, scientists have recorded gravitational waves from the merger of two neutron stars - super-dense objects with a mass the size of our Sun and the size of Moscow, reports the N+1 website.

The subsequent gamma-ray burst and kilonova burst were observed by about 70 ground-based and space observatories - they were able to see the process of synthesis of heavy elements predicted by theorists, including gold and platinum, and confirm the correctness of the hypotheses about the nature of the mysterious short gamma-ray bursts, the press service of the collaboration reports LIGO/Virgo, European Southern Observatory and Los Cumbres Observatory. The observational results may shed light on the mystery of the structure of neutron stars and the formation of heavy elements in the Universe.

Gravitational waves are waves of vibrations in the geometry of space-time, the existence of which was predicted by the general theory of relativity. The LIGO collaboration first reported their reliable discovery in February 2016 - 100 years after Einstein’s predictions.

Reportedly, on the morning of August 17, 2017 (at 8:41 a.m. East Coast time, when it was 3:41 p.m. in Moscow), automatic systems on one of the two detectors at the LIGO gravitational-wave observatory detected the arrival of a gravitational wave from space. The signal was designated GW170817, the fifth time gravitational waves have been detected since they were first detected in 2015. Just three days earlier, the LIGO observatory “heard” a gravitational wave for the first time, together with the European Virgo project.

However, this time, just two seconds after the gravitational event, the Fermi space telescope recorded a flash of gamma rays in the southern sky. Almost at the same moment, the European-Russian space observatory INTEGRAL saw the flash.

LIGO's automated data analysis systems concluded that the coincidence of these two events is extremely unlikely. During the search for additional information, it was discovered that the gravitational wave was also seen by the second LIGO detector, as well as the European Virgo gravitational observatory. Astronomers around the world were put on alert - many observatories, including the European Southern Observatory and the Hubble Space Telescope, began hunting for the source of gravitational waves and a gamma-ray burst.

The task was not easy - the combined data from LIGO/Virgo, Fermi and INTEGRAL made it possible to outline an area of ​​35 square degrees - this is the approximate area of ​​​​several hundred lunar disks. Only 11 hours later, the small Swope telescope with a meter-long mirror located in Chile took the first image of the alleged source - it looked like a very bright star next to the elliptical galaxy NGC 4993 in the constellation Hydra. Over the next five days, the brightness of the source dropped by a factor of 20, and the color gradually shifted from blue to red. All this time, the object was observed by many telescopes in the ranges from X-ray to infrared, until in September the galaxy was too close to the Sun and became inaccessible for observation.

Scientists concluded that the source of the flare was in the galaxy NGC 4993 at a distance of about 130 million light years from Earth. This is incredibly close; until now, gravitational waves have come to us from distances of billions of light years. Thanks to this proximity, we were able to hear them. The source of the wave was the merger of two objects with masses in the range from 1.1 to 1.6 solar masses - these could only be neutron stars.

Localization of the source of gravitational waves in the galaxy NGC 4993

The burst itself “sounded” for a very long time - about 100 seconds; bursts lasting a fraction of a second were produced. A pair of neutron stars revolved around a common center of mass, gradually losing energy in the form of gravitational waves and moving closer together. When the distance between them was reduced to 300 km, the gravitational waves became powerful enough to fall into the sensitivity zone of the LIGO/Virgo gravitational detectors. The neutron stars managed to complete 1.5 thousand revolutions around each other. When two neutron stars merge into one compact object (a neutron star or a black hole), a powerful burst of gamma radiation occurs.

Astronomers call such gamma-ray bursts short gamma-ray bursts; gamma-ray telescopes detect them about once a week. The reported brief gamma-ray burst from the neutron star merger lasted 1.7 seconds.

If the nature of long gamma-ray bursts is more clear (their sources are supernova explosions), then there was no consensus on the sources of short bursts. There was a hypothesis that they are generated by mergers of neutron stars.

Now scientists have been able to confirm this hypothesis for the first time, since thanks to gravitational waves we know the mass of the merged components, which proves that these are neutron stars.

"For decades we have suspected that short gamma-ray bursts produce neutron star mergers. Now, thanks to data from LIGO and Virgo about this event, we have the answer. Gravitational waves tell us that the merging objects had masses corresponding to neutron stars, and a gamma-ray burst says "that these objects were unlikely to be black holes, since black hole collisions should not produce radiation," says Julie McEnery, Fermi project scientist at NASA Goddard Space Flight Center.

Source of gold and platinum

In addition, astronomers for the first time received unambiguous confirmation of the existence of kilonova (or “macron”) flares, which are approximately 1 thousand times more powerful than ordinary novae flares. Theorists predicted that kilonovae could arise from the merger of neutron stars or a neutron star and a black hole.

This triggers the process of synthesis of heavy elements, based on the capture of neutrons by nuclei (r-process), as a result of which many of the heavy elements such as gold, platinum or uranium appeared in the Universe.

According to scientists, one kilonova explosion can produce a huge amount of gold - up to ten times the mass of the Moon. So far, only once has an event that could have been a kilonova explosion been observed.

Now, for the first time, astronomers were able to observe not only the birth of a kilonova, but also the products of its “work.” Spectra obtained using the Hubble and VLT (Very Large Telescope) telescopes showed the presence of cesium, tellurium, gold, platinum and other heavy elements formed during the merger of neutron stars.

11 hours after the collision, the temperature of the kilonova was 8 thousand degrees, and its expansion speed reached about 100 thousand kilometers per second, notes N+1, citing data from the Sternberg State Astronomical Institute (SAI).

ESO said the observation matched almost perfectly with the prediction of how the two neutron stars would behave during a merger.

"So far, the data we have obtained is in excellent agreement with the theory. This is a triumph for theorists, a confirmation of the absolute reality of the events recorded by LIGO and VIrgo observatories, and a remarkable achievement for ESO, which was able to obtain such observations of a kilonova," says Stefano Covino, first author of one of the articles in Nature Astronomy.

This is how astronomers saw the collision of neutron stars

Scientists do not yet have an answer to the question of what remains after the merger of neutron stars - it could be either a black hole or a new neutron star, in addition, it is not entirely clear why the gamma-ray burst turned out to be relatively weak.