A team of astronomers from the Niels Bohr Institute and the DAWN research center published an article in the journal Astronomy & Astrophysics. They reported on the study of the merger of two neutron stars.
Kilonova explosion
In 2017, detectors of the LIGO-Virgo network captured a gravitational-wave burst whose source was located in the galaxy NGC 4993, which is 130 million light-years away from the Milky Way. It was created by the merger of two neutron stars.
This event led to the formation of the smallest black hole observed so far. But the consequences went beyond that. The collision resulted in a fireball expanding almost at the speed of light. In the days that followed, it shone with a luminosity comparable to hundreds of millions of suns. This object, called a kilonova, shone so brightly because of the decay of heavy radioactive elements formed during the merger.
This event, not surprisingly, instantly attracted the attention of the scientific community. Observations of the kilonova have been joined by many observatories, from ESO’s Very Large Telescope to Hubble. By combining the data they have collected, an international team of researchers has come closer to unraveling where the chemical elements that make up our planet and all of us came from.
The fact is that in the interior of even the most massive stars cannot form elements heavier than iron. Therefore, they should have some other source of origin. Neutron star collisions are considered the best candidate.
Big Bang in miniature
According to the science team, the kilonova explosion reminded them of the Universe in miniature as it was at the time of the Big Bang. Immediately after the collision, the shattered stellar matter had a temperature of many billions of degrees. It was a thousand times hotter than the center of the Sun and was comparable to the temperature of the Universe one second after the Big Bang. Such conditions are impossible to replicate in any Earth laboratory.
Such extreme temperatures led to the fact that the electrons were not attached to atomic nuclei, but floated in the so-called ionized plasma. As it cooled, neutral atoms and then heavy elements began to form from it. It was similar to the process that occurred after the Big Bang when heavy metals began to form. In the afterglow of kilonova, scientists were able to detect traces of strontium and yttrium. Most likely, other heavy elements were also synthesized.
Observations of the kilonova explosion have shown that scientists can experimentally confirm the basic theories of the evolution of the Universe and observe processes similar to the ones that occurred after the Big Bang. They also demonstrated the importance of different observatories working together. No one, even the most powerful telescope, individually would have been able to get the data that the scientists needed.
Provided by nbi.ku.dk
