Neutron stars turned out to be "factories" of heavy elements

Scientists recorded for the first time that strontium can form after the collision of neutron stars.

What elements do neutron stars produce? picture of supernova
What elements do neutron stars produce?

Observations of the merger of two neutron stars in the constellation Hydra helped astrophysicists to prove that such cosmic cataclysms do generate large amounts of heavy elements.

The researchers' findings were published by the scientific journal Nature.

What elements do neutron stars produce?

Scientists re-analyzed the data collected during observations of the merger as early as 2017, and found traces that at least one heavy element - strontium - was present in the "wreckage" of colliding neutron stars. 

This may prove that such cataclysms have given rise to almost all the reserves of this element in the universe.

After the Big Bang, there were only three elements in the universe - hydrogen, helium and trace amounts of lithium. 

After about 300-500 million years, when the first stars appeared and died, it began to gradually fill with heavier elements, which were formed during the thermonuclear reactions in the bowels of the stars.

Today, physicists believe that all elements heavier than iron, including gold, uranium, as well as other heavy and rare earth metals, have emerged for the most part as a result of supernova explosions, as the temperature and pressure inside the "normal" stars is too low for their rapid formation.

Relatively recently, cosmologists have faced a new problem. 

Estimates of the rate of formation of gold and other heavy elements that gave rise to supernovae indicated that as a result of such outbreaks the right amount of some astronomical "metals" could not have formed. 

This suggests that other, more exotic processes, such as neutron star collisions, may have been involved in their birth.

Neutron stars are one of the most concentrated sources of particles, which are needed for the so-called R-process

This is what astrophysicists call chains of thermonuclear reactions, during which lighter nuclei turn into gold and other heavy elements.

"Factory" of heavy elements

The first hints that this is indeed the case, scientists received in August 2017, when the gravitational observatories LIGO and ViRGO recorded fluctuations in space-time that arose as a result of the merger of the two pulsars in NGC 4993 in the constellation Hydra.

Researchers had to spend almost two years re-analyzing the data to find the first real traces of the process - the strontium atoms, the 38th element of mendeleev's periodic table. 

To do this, the scientists studied in detail how the spectrum of the light changed in the first hours and days after its detection. In doing so, they analyzed the absorption and radiation lines, presumably related to the elements that generate the R-process. 

This task was complicated by the fact that the remains of neutron stars during the explosion accelerated to near the speed of light.

Astronomers were able to circumvent this problem by using data on how often different elements of similar processes within the Sun and other stars are generated.

According to the researchers, they were surprised to find the formation of strontium, but this was not a complete surprise. 

On the one hand, scientists assumed that they would find traces of heavier elements in the hot cloud of gas that surrounds dead neutron stars in the galaxy NGC 4993, scientists have not yet found all these elements.

On the other hand, as the observations of the Sun and other ordinary stars have shown, in such explosions strontium should form much more than other heavy astronomical "metals". 

Therefore, its discovery, according to scientists, does not contradict the current ideas. It simply indicates that small differences in the nature of neutron star mergers can significantly change what elements these "space factories of matter" will produce.

For the first time, researchers directly linked the birth of new heavy element atoms as a result of the collision of lighter nuclei with neutrons.