Astronomers calculated the origin of all chemical elements and wondered: where is there so much gold in the universe? The fact is that there are not enough known processes to explain the observed abundance of this precious metal.
Details are set out in a scientific article published in the Astrophysical Journal.
Astronomers believe that the earliest atomic nuclei appeared in the era of primordial nucleosynthesis, which began in the first seconds after the Big Bang and lasted several tens of minutes. At the same time, almost all the hydrogen available in the Universe was formed, a significant part of helium, a certain amount of lithium and an insignificant amount of beryllium and boron. All these chemical elements are light and are located at the very beginning of the periodic table.
The appearance of all the other atomic nuclei is somehow connected with the stars. New nuclei are formed in the bowels of all the stars without exception, as well as in the atmospheres of red giants, during supernova explosions and collisions of neutron stars.
What contribution does each of these processes make to the formation of certain chemical elements? This remains a matter of controversy.
The authors of the new study were the first to calculate the process of formation of all stable nuclei from carbon to uranium from first principles. This means that they solved the equations of nuclear physics in all their complexity, without resorting to simplifying assumptions.
These calculations made it possible to find out how much of this or that element is formed in a typical small star, in one supernova explosion, and so on. Based on this, scientists calculated the role of various celestial bodies and the events occurring with them in the huge chemical complex of the Universe.
It turned out, for example, that small stars that do not explode like supernovae produce half of all carbon in the universe. The second half falls on massive luminaries that end their lives in a supernova explosion.
It is supernovae, according to the authors, that supply the universe with iron. Moreover, half of it falls on explosions of massive stars, and another half – on type Ia supernovae, that is thermonuclear explosions of white dwarfs .
However, the most unusual result concerns gold. In previous studies, the origin of the noble metal was attributed to collisions of neutron stars. Now scientists have questioned this.
“Even the most optimistic estimates of the neutron-star collision rate simply cannot explain the apparent abundance of this element in the universe,” says co-author Amanda Karakas of Monash University in Australia. “It came as a surprise.”
However, astronomers already have their own version of the origin of gold. They speculate that the problem is in supernovae of an unusual type. Explosions of very massive stars with strong magnetic fields could provide space with the observed amount of gold, experts say.
At the same time, the authors do not deny the contribution of collisions of neutron stars to the synthesis of other chemical elements .