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The existence of heavy elements such as precious metals is due to neutron star collisions, current theory holds. But something is wrong in math because colliding neutron stars couldn’t produce as much gold as there is in the universe today.
Neutron star collisions do not produce as many chemical elements as we previously assumed, according to a recent analysis of the evolution of galaxies published by Australian astronomers in the Astrophysical Journal. The research, for example, says that current models cannot explain why we see so much gold in the universe – that is, we are faced with another astronomical mystery.
One figure in the article is a redefined periodic table in which the background of each natural element is quenched according to its astronomical origin. All hydrogen atoms in the universe, including all hydrogen on Earth, were formed in the Big Bang. The Big Bang also produced significant amounts of helium and lithium, while almost nothing else. Each of the other natural elements was created by nuclear processes within stars. The mass of a star determines what elements it is capable of creating and then, at the end of the star’s life, all the matter it produces is dispersed into its own galaxy. This scattering occurs explosively in the case of really large stars, and in the form of dense fluxes like the solar wind in the smallest of the size class of our Sun.
Green: elements formed by the explosion of luminous stars.
Blue: elements formed by the explosion of massive stars
Red: elements formed by the explosion of white dwarfs
Purple: elements formed by the collision of neutron stars.Source: Chiaki Kobayashi et al Artwork: Sahm Keily
We can think of stars as huge pots into which new elements are spilled. Explains Amanda Karakas, a staff member at the Australian Center of Excellence in Astrophysics in 3 Dimensions (ASTRO 3D). “The nuclear reactions that extract these elements are the same ones that keep stars shining for billions of years. As the stars age and the interior warms, they create heavier and heavier elements. “
It is currently believed that half of the elements heavier than iron, such as thorium and uranium, are formed when super dense burned stellar remnants, called neutron stars, collide with each other. Although theories have long assumed this, the neutron star collision was only first observed in 2017 by observation.
Now, however, the latest analysis published by Karakas et al., Chiaki Kobayashi, and Maria Lugaro concludes that previous theories may have greatly overestimated the role of colliding neutron stars in element formation, and an entirely different astrophysical process may be responsible for creating most of the heavy elements.
Special supernovae
“Neutron star mergers did not produce enough heavy elements during the early life of the universe, and it is no different now, 14 billion years later,” Karakas stated. “The universe could not have created them so quickly as to explain their presence in very old stars, and in general there are not as many neutron star collisions as would be necessary to produce the heavy elements in the quantities we see today.
The researchers, on the other hand, suggest that heavy elements can result from an entirely different process: in abnormal supernovae that collapse spinning very rapidly while generating strong magnetic fields. This theory is just one of the results of an article published in the latest issue of the Astrophysical Journal. The study is the first to deduce the origins of all natural elements, from carbon to uranium, down to the theoretical foundations.
The new model will fundamentally redesign our current picture of the evolution of the universe, say the authors. “We built the new model by explaining the origins of all the elements at once, in a single frame, and found, for example, that it produced enough silver but very little gold,” said Kobayashi, a professor at the University of Hertfordshire, England. – Because our model overproduces silver compared to observations, but does not generate enough gold, a hitherto unknown starburst or nuclear reaction has yet to be identified. “
The study clarifies the relative roles of mass, age, and arrangement of stars in creating different elements. The researchers find, among other things, that stars less than eight times the mass of the sun produce carbon, nitrogen and fluorine, and produce half of the elements heavier than iron. Giant stars more than eight times the mass of the sun, which end their lives in a supernova explosion, produce most of the elements ranging from carbon to iron, including the carbon and calcium necessary for life.
“Apart from the hydrogen that was formed in the Big Bang, there is no element that can be created by just one type of star,” explains Kobayashi. “Half of the carbon comes from low-mass dying stars and the other half from supernovae. Half of the iron is formed in normal supernova explosions from giant stars, while the rest is formed in a different type of explosion, the Type Ia supernova. The latter is characteristic of the smaller stars that form the even system. “
The possible source
The gravitational pairs of giant stars, on the other hand, can become neutron stars, which can collide with some of the heaviest elements found in nature during giant star fusion, such as gold. In the calculation of the new model, however, the mathematics simply did not come to light. “Even if we estimate the frequency of neutron star collisions as generously as possible, we cannot explain how these elements can populate the universe in observed abundance,” Karakas emphasized. “We were surprised by this ourselves. It appears that spinning supernovae with a strong magnetic field could be the true birthplaces of most heavy elements. “
One of the article’s co-authors, Maria Lugaro, who, in addition to the Australian University of Monash, also conducts research at the Konkoly Thege Miklós Observatory in Budapest, believes that the mystery of the lost gold will soon be solved. “The study of rare nuclei formed by neutron star fusion at nuclear research institutes in Europe, the United States and Japan is expected to lead to new discoveries,” she said. – We still do not know the characteristics of these nuclei, but the truth is that they are closely related to the formation of heavy elements. The astrophysical question of lost gold will likely be answered by a nuclear physics experiment. “
The authors predict that future research may still conclude that neutron star collisions are more frequent than we think based on the data now available. In this case, we will obviously have to re-evaluate their contribution to the formation of elements that help our lives in so many places and ways, from our cell phones to their screens to the fuel in our nuclear reactors.
However, if this is not the case, the current conclusion remains that these gigacollisions, at least when it comes to creating heavy elements, have more smoke than flames.
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