On Monday it became known about the unprecedented phenomenon was first recorded by scientists of the LIGO and Virgo gravitational waves from the merger of two neutron stars. This event is called the beginning of a new era in astrophysics, but why is it so important?
We talked to Alan Jay Weinstein is Professor of physics and head of the group for the analysis of astrophysical data from the LIGO laboratory at the California Institute of technology. He told why the incident is so important, and how it can change the existing understanding of the Universe.
Everyone says there was «unprecedented» phenomenon. What is its significance?
The first time our scientific team and the LIGO detectors have detected gravitational waves in September 2015, the collision of two black holes. This confirmed the major hypothesis of the theory of relativity, gave us new possibilities for the study of black holes, allowed to witness a powerful phenomenon since the Big Bang and, to some extent, gave the opportunity to hear the vibrations of space-time. Since then we have fixed several similar phenomena.
But August 17, 2017, we saw something else. It was a combination of two ultra-compact bodies – not black holes, and neutron stars. They consist of pure nuclear material, so it is very exotic and interesting topic for physicists and astronomers. But the important thing is that, unlike black holes, they emit light in large quantities.
Gravitational waves
Gravitational waves, predicted by General relativityis the change of the gravitational field, which are distributed according to the principle wave. They can be described as «ripples of space-time».
They were first discovered in 2015 detectors LIGO Observatory. In 2017 American physicists Weiss, Thorne and Barish received the Nobel prize for experimental detection of gravitational waves from the merger of two black holes.
The term «gravitational wave» was introduced by Poincare in 1905.
The first time we witnessed such a large-scale astronomical phenomena, which were a source of gravitational waves and light. We watched the light in all its many manifestations: not only visible light but also ultraviolet, infrared, x-ray and gamma radiation, radio waves.
So we were able to «see» and «hear» this extraordinary phenomenon in a variety of ways. The incident confirmed the link between the merging of binary neutron stars and gamma ray bursts (GRB), identified the likely location for the synthesis of heavy elements in the universe, allowed us for the first time to measure the speed and polarization of gravitational waves. Due to gravitational waves event was the beginning of the era of multi-messenger astronomy.
Multi-messenger astronomy
The term multi-messenger astronomy is still no official counterpart in the Russian language. This field of astronomy is based on the coordinated observation and interpretation of the signals, creating, through a variety of astrophysical processes, electromagnetic radiation, gravitational waves, neutrinos and cosmic rays. So they reveal different information about their sources.
As a rule, sources are ultracomplete pairs of black holes and neutron stars, supernovae, irregular neutron stars, gamma-ray bursts active galactic nuclei and relativistic jets.
Now physicists and astronomers have the opportunity to learn a lot about this incredibly multi-faceted process, we still continue to investigate the incident and to learn something new. But if to speak about the importance of this event in a practical and universal sense, it gives us information about the origin of the heaviest chemical elements, including precious metals in our jewelry.
The collision appeared gold, lead and platinum. The person is not too close to the world of science (like me) sees it like a blast of Golden dust, but of course much more complicated.
A neutron star is a pure nuclear material, which, in a collision, ejected into interstellar space in large numbers. It is split and then combined in neutron-rich atomic nuclei, which are heavy elements — not only gold, lead and platinum, but also uranium, plutonium, most of the heaviest elements in the periodic table. They are scattered along the galaxy (which, if GW170817very far).
Such a collision happen in our milky Way about once in 10-100 thousand years. Remaining fragments of heavy elements get to our solar system and on Earth.
Neutron stars
A neutron star is a dense neutron core with a thin shell, which is formed in the supernova explosion. Neutron stars have a strong magnetic field and high density, but their size is 10-20 km A neutron star have great speed – several hundred revolutions per second.
Collision is important for a number of reasons. Already say that it will be the beginning of a new era for astronomy. Is it really so?
Yes! We find many similar phenomena, different stellar masses at different galactic environments. This will allow us to learn much about the formation, development and extinction of the most massive stars, and to foster new understanding of the origin of the heaviest chemical elements. The results of these studies will appear in the textbooks, so when we’re talking about a bright future, or even gold, really mean it.
The clash provided a new opportunity to study gravitational waves and the Universe. Scientists learn what’s new with this discovery?
We can measure the expansion rate of the Universe with ever improving precision. There are many ways to do it, but we have another completely new method. If in all cases we will come to the same conclusions, we will increase our understanding of the Big Bang. If not, then we will know that misunderstood some data in need of better theory, or missed something important.
We are going to the study of fundamental properties of gravitational waves more accurate information. This will allow us to expose the General theory of relativity, the modern theory of gravity, even more severe test. We suspect that in the end we find that she is not quite true, and it will point to a more deep and precise theory.
The General theory of relativity (GTR)
In 1915 albert Einstein published his geometric theory of gravity, which became known as the General theory of relativity. Its main assertion was that the gravitational and inertial forces are of the same nature, which showed that the deformation of space-time causes gravity effects.
Einstein used the gravitational field equations to link the matter and the curvature of space-timein which it existed – this was the difference between the work from other alternative theories of gravity.
The General theory of relativity predicted effects such as gravitational time dilation, gravitational light bending, gravitational redshift of light, gravitational radiation, signal delay in the gravitational field, etc. in addition, it predicted the existence of black holes.
At the present day remains the most successful theory of gravity.
Something like the collision of neutron stars occurs extremely rarely. When scientists witness something like that again?
Such phenomena can be observed in the milky Way every 10-100 thousand years. We don’t have to wait so long! Our current LIGO detectors are able to observe these collisions in distant galaxies, more than a million. Now we are improving the sensitivity of our detectors to be able to record these phenomena in the hundreds of millions of galaxies. So we hope to see something like that every year.
