Large atoms require a lot of energy to construct. A new model of quantum interactions now suggests that some of the lightest particles in the universe may play a crucial role in the formation of at least some heavy elements.
Physicists in the US have shown how subatomic ‘ghost particles’ known as neutrinos can force atomic nuclei to become new elements.
Not only would this be a completely different method for building elements heavier than iron, it could also describe a long-assumed “intermediate path” that straddles the border between two well-known processes, nuclear fusion and nucleosynthesis.
For most elements larger than hydrogen, the warm embrace of a large, bright star is enough to overcome protons and neutrons’ strong need to push apart long enough for other close-range interactions to take over. This fusion embrace releases extra energy, keeping the cores of stars nice and warm.
Once atoms are about 55 nucleons in size – the mass of an iron nucleus – the addition of extra protons requires more energy than the fusion process can ever repay.
This shift in thermonuclear economics means that the heavies of the periodic table can only form when extra neutrons stick to the solidifying mass of nuclear particles long enough for one to decay and regurgitate an electron and a neutrino, transforming it into the extra proton needed to qualify as a nuclear particle. new element.
Normally, this process is painfully slow, trickling out over decades or even centuries as nuclei in large stars jostle, often gaining and losing neutrons, with few ever making the switch to proton capping at the critical moment.
Given enough power, this growth can also happen surprisingly quickly – within minutes in the hot mess of collapsing and colliding stars.
But some theoretical physicists have wondered whether there are other routes, intermediate paths, between the slow ‘s’ process and the fast or ‘r’ process.
“Where the chemical elements are made is not clear, and we don’t know all the possible ways they could be made,” said physicist Baha Balantekin, lead author of the study from the University of Wisconsin.
‘We believe that some were formed during supernova explosions or neutron star mergers, and that many of these objects are subject to the laws of quantum mechanics, so you can use the stars to investigate aspects of quantum mechanics.’
A solution may well be found in the quantum nature of the flood of neutrinos – the most abundant particles with mass in the universe – spilling out into cosmic environments.
Although they are virtually massless and have virtually no means of making their presence known, their enormous numbers mean that the emission and occasional absorption of these short-lived ‘ghost particles’ still influence the budgets of protons and neutrons found deep within massive stars and cataclysmic cosmic stars buzzing around. events.
A bizarre quirk of the neutrino is its habit of oscillating within a quantum haze, switching between different flavors of identity as it flies through empty space.
Modeling huge numbers of neutrinos spinning and flopping in a chaotic nucleon soup is easier said than done. Therefore, physicists will often treat them as a single system, treating the properties of individual particles as one large, entangled superparticle.
Balantekin and his colleagues at George Washington University and the University of California, Berkeley, used the same approach to better understand how the wind of neutrinos emitted by a newborn neutron star colliding nearby might serve as an intermediate process of nucleosynthesis .
By determining the extent to which the quantum identity of individual neutrinos depends on the size of this entangled state, the team found that this ghostly storm could generate a significant amount of new elements.
“This paper shows that if the neutrinos are entangled, there is an improved new process for producing elements, the i-process,” says Balantekin.
While the numbers make sense in theory, testing the idea is a completely different matter.
Studying the interactions of “ghostly” neutrinos on Earth is still in its infancy, leaving researchers staring into the vast reaches of space for evidence of new ways the largest elements come together.
This research was published in The Astrophysical Journal.