Astronomers first heard gravitational waves from merging neutron stars

Astronomers first heard gravitational waves from merging neutron stars

Scientists for the first time in the history of recorded gravitational waves from the merger of two neutron stars — super dense objects with mass of our Sun and the size of Moscow.

Then caused a gamma-ray burst and flash bulanovoi watched about 70 ground-based and space-based observatories — they were able to see theorists predicted the synthesis of heavy elements, including gold and platinum, and to confirm the correctness of the hypotheses about the nature of the mysterious short gamma-ray bursts, according to the press service of the collaboration LIGO/Virgo, the European southern Observatory and the Observatory, Los Cumbres. The results of observations may shed light on the mystery of the structure of neutron stars and the formation of heavy elements in the Universe.

On the morning of August 17, 2017 (8:41 on the East coast of the United States, when in Moscow 15:41) automatic system at one of two detectors gravitational-wave Observatory LIGO registered the arrival of gravitational waves from space. The signal received the designation GW170817, it was already the fifth case of fixation of gravitational waves from 2015, from when they were first registered. Just three days before the LIGO Observatory for the first time “heard” gravitational wave together with the European project Virgo.

This time, two seconds after gravitational events space telescope Fermi has recorded a flash of gamma radiation in the southern sky. Almost at the same time the flash saw the European-Russian space Observatory INTEGRAL.

Automatic data analysis systems Observatory LIGO came to the conclusion that the coincidence of these two events is extremely unlikely. In seeking additional information, it was discovered that the gravitational wave saw the second LIGO detector, as well as the European gravitational Observatory, Virgo. Astronomers around the world were raised by alarm — the hunt for the source of the gravitational waves and gamma-ray burst began many observatories including the European southern Observatory and space telescope Hubble.

The task was not easy — the combined data LIGO/Virgo, Fermi, and INTEGRAL allowed us to outline the region with an area of 35 square degrees is the approximate size of several hundred lunar disk. Only 11 hours light meter Swope telescope with a mirror located in Chile, made the first the possible cause — he looked like a very bright star next to the elliptical galaxy NGC 4993 in the constellation Hydra. Over the next five days, the source brightness fell 20 times, and the color gradually shifted from blue to red. All this time the object was observed by many telescopes in the range of x-ray to the infrared, while in September, the galaxy was not too close to the Sun, and was not available for observation.

Scientists came to the conclusion that the source of the outbreak was located in the galaxy NGC 4993 at a distance of about 130 million light years from Earth. It’s incredibly close, so far gravitational waves come to us from distances of billions of light years.

Thanks to this proximity, we were able to hear them. The source wave was a merger of two objects with masses in the range from 1.1 to 1.6 solar masses — it could only be a neutron star.

The surge “was” a very long time — about 100 seconds, mergers of black holes gave bursts lasting fractions of a second. A pair of neutron stars rotate around a common center of mass, gradually losing energy in the form of gravitational waves and getting closer. When the distance between them was reduced to 300 kilometers, the gravitational waves become powerful enough to get into the zone of sensitivity of the gravitational detectors LIGO/Virgo. At the time of the merger of two neutron stars into a single compact object (neutron star or black hole) is powerful flash of gamma radiation.