Colliding neutron stars produce smaller sizes of gold, creating an astronomical mystery

The concept of this artist portrays two neutron stars at the moment of collision. Credit: Dana Berry, SkyWorks Digital, Inc.

Colliding neutron stars were touted as the main source of some of the heaviest elements in the periodic table. Now, not so much…

Neutron star collisions do not create the amount of chemical elements already assumed, a new analysis of the evolution of the galaxy finds.

Research also suggests that current models cannot explain the amount of gold in the universe – creating an astronomical mystery.

This work has produced a new periodic table, showing the naturally occurring stellar origin from carbon to uranium.

All the hydrogen in the universe – including every molecule on Earth – was created by big Bang, Which produced a lot of helium and lithium, but not much.

The rest of the naturally occurring elements are formed by various atomic processes occurring inside the wires. The mass actually controls which elements are lattice, but they are all released into galaxies at the last moments of each star – indeed in the case of larger ones, or in the case of dense outflows, similar to solar wind, the Sun. For people in the same class as.

“We can think of stars as giant pressure cookers,” said Associate Professor Karakas, co-author of Australia’s ARC Center of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D).

Periodic table naturally recurring element

Periodic table, naturally occurring elements up to uranium. The shading indicates stellar origin. Sincerely: Chika Kobayashi et al. Artwork: Sahm Keiley

“The reactions that make up these elements also provide energy that keeps the stars shining for billions of years. As stars age, they produce heavier and heavier elements as heat is produced inside them. ”

Half of all the elements that are heavier than iron – such as thorium and uranium – were thought to form when neutron stars, superdances of the burnt sun, crash into each other. Long principles, neutron star The collision was not confirmed until 2017.

Now, however, the latest analysis conducted by Caracas and fellow astronomers Chiaki Kobayashi and Maria Lugaro suggests that the role of neutron stars has largely diminished – and that a more stellar process completely forms most of the heavier elements Is responsible for

“The Neutron Star merger did not produce enough heavy elements in the early life of the Universe, and they still do not, 14 billion years later,” Karakas said.

“The universe did not make them fast enough for their presence in very ancient stars, and, overall, there is not enough collision going on around today to account for the abundance of these elements.”

Instead, the researchers found that heavier elements must be formed by a completely different kind of stellar phenomena – unusual supernovas that rotate very rapidly and produce strong magnetic fields.

The discovery is one of several to emerge from his research, which has just been published Astrophysical Journal. His study is the first time the first origin of all naturally occurring elements from carbon to uranium has been calculated from first principles.

The new modeling, the researchers say, will substantially change the currently accepted model of how the universe evolved. “For example, we built this new model to explain all the elements at once, and found not enough silver but enough gold,” said Associate Professor Kobayashi, co-author at the University of Hertfordshire in the UK.

“Silver is produced more, but gold is produced in the model compared with the observations. This means that we may need to identify a new type of stellar explosion or nuclear reaction. ”

The study refines previous studies that calculate the relative roles of star mass, age, and order in the production of elements.

For example, researchers established that stars about eight times smaller than the Sun’s mass produce carbon, nitrogen, and fluorine, with half of all elements being heavier than iron.

Around eight times the stars of the Sun’s mass, which also explode at the end of their lives as supernovas, produce many elements from carbon through iron, including most of the oxygen and calcium needed for life.

“Apart from hydrogen, there is no single element that can be formed from only one type of star,” Kobayashi explained.

“Half of the carbon is produced from low-mass stars, but the other half comes from supernovae.

“And half of the iron comes from the normal supernova of large stars, but the other half requires another form, called Type Ia Superova. These are manufactured in the binary system of low-mass stars.”

Couples of gravitationally bound stars can, by contrast, turn into neutron stars. When they collide, the effect produces some of the heaviest elements found in nature, including gold.

In new modeling, however, the number is not simply adding.

“Even the most optimistic estimates of the frequency of neutron star collisions cannot account for the abundance of these elements in the Universe,” Karkas said. “It was a surprise. It seems that spinning supernovas with strong magnetic fields is the real source of most of these elements. ”

The co-authors, who held positions at the Konkoli Observatory in Hungary and Monash University in Australia, are Dr. Maria Lugaro feels that the mystery of the missing gold can be solved soon.

He said new discoveries are expected from nuclear facilities around the world, including Europe, the US and Japan, currently targeting rare nuclei associated with the neutron star merger.

“The properties of these nuclei are unknown, but they control the production of heavy element abundance. The missing gold astronomical problem can actually be solved by a nuclear physics experiment. ”

Researchers considered that future research could find that the neutron star’s collisions are more persistent than the evidence so far, in which case their contribution to the elements that range from mobile phone screens to fuel for nuclear reactors Some make, they can be modified upwards again.

However, at the moment, they pay very little money for their bangs.

Reference: 15 September 2020, Astrophysical Journal.
DOI: 10.3847 / 1538-4357 / abae65