In a recent paper published recently in the journal Astronomy & Astrophysics, scientists reported on months of observing the explosion following the merger of two neutron stars. It’s like the Big Bang in miniature, astrophysicists found, hour by hour they reconstructed the processes that took place during and after the explosion, including the recombination of electrons with atoms and the formation of matter.
Artistic representation of a kilonova explosion. Image source: ESO
A unique event was discovered and identified on August 17, 2017. Two weeks earlier, the third gravitational wave detector, the French-Italian Virgo Observatory, began operating. In addition to the two detectors of the American LIGO gravitational-wave observatory, the appearance of a third detector has made it possible to localize the source of gravitational waves with unprecedented accuracy. This is how the event GW170817 was recorded – a gravitational wave burst from the merger of two neutron stars.
When two neutron stars merged, it resulted in a massive explosion that is now called a kilonova. The energy of such explosions can be 1000 times higher than the brightness of a regular supernova explosion. This event received its own index – AT2017gfo, although it is derived from the merger of neutron stars.
Thanks to the rapid localization of the event and subsequent observations of it by dozens of ground and space observatories in all possible ranges, it was possible to collect a lot of data, the first comprehensive understanding of which appears only now, seven years after the event. And the whole turns out to be incredibly informative, even though even the first results were considered a breakthrough in astronomical observations.
According to scientists, they practically observed the events of the Big Bang in miniature. Today we detect the cosmic microwave background radiation around us, and the hourly observation of the kilonova AT2017gfo made it possible to see the processes before, during and after its appearance. Scientists observed how from the hot plasma, when there was no matter yet at the site of the kilonova explosion, electrons began to unite with atoms (recombine) and form neutral atoms – heavy elements that are born in the Universe only during such “energetic” events.
In the afterglow of the AT2017gfo event, scientists discovered strontium and other heavy metals. In stars, the energy of thermonuclear fusion is only enough to form iron atoms. During the kilonova explosion, the temperature rose to billions of degrees, which can be correlated with the temperature of the Big Bang, after which heavy metal atoms also began to form. This cannot be reproduced in any earthly laboratory. And there are not many celestial laboratories for observing such processes yet. But the AT2017gfo event showed that we can experimentally (observationally) prove the basic theories of the birth and evolution of the Universe. And even watch the “Big Bang” and its consequences.