Unknown Trans-Uranic Elements Suspected In Very Dense Asteroids

Written by Mohammad Qusir Rather on October 17, 2023. Posted in Current News

Some asteroids have measured densities higher than those of any elements known to exist on Earth. This suggests that they are at least partly composed of unknown types of “ultradense” matter that cannot be studied by conventional physics

Jan Rafelski and his team at the Department of Physics, The University of Arizona, Tucson, U.S., suggest that this could consist of superheavy elements with atomic number (Z) higher than the limit of the current periodic table.

They modeled the properties of such elements using the Thomas-Fermi model of atomic structure, concentrating particularly on a proposed “island of nuclear stability” at and around Z=164 and extending their method further to include more exotic types of ultra-dense material.

This work has now been published in The European Physical Journal Plus.

Superheavy elements are defined as those with a very high number of protons (high atomic number), generally considered to be those with Z>104. They can be divided into two groups.

Those with atomic numbers between 95 and 118 have been made experimentally but are radioactive and unstable with very short half-lives and, therefore, are only of academic and research interest.

Elements above 118 have not yet been observed, but properties have been predicted for some of them.

In particular, an “island of nuclear stability” is predicted at about Z=164. And as, in general, the density of elements tends to rise with their atomic mass, these superheavy elements can be expected to be extremely dense.

The densest stable element is the rare platinoid metal osmium (Z=76); its density of 22.59 g/cm3 is about twice that of lead. Objects—typically, astronomical bodies—with densities higher than that are considered “compact ultradense objects” or CUDOs.

The most extreme example known is the asteroid named 33 Polyhymnia, which is located in the main belt between Mars and Jupiter; its density has been calculated as about 75 g/cm3. Rafelski proposes that Polyhymnia and similar objects may be composed of elements above Z=118, possibly with other types of ultradense matter.

Rafelski and his two student co-workers, Evan LaForge and Will Price set out to calculate the microscopic atomic structure and properties of ultraheavy elements using the relativistic Thomas-Fermi model of the atom.

“We chose this model, despite its relative imprecision, because it allows the systematic exploration of atomic behavior as a function of atomic number beyond the known periodic table,” Rafelski explains. “A further consideration is that it also enabled us to explore many atoms in the short time available to Evan [LaForge], our brilliant undergraduate student.”

The researchers’ calculations confirmed the prediction that atoms with around 164 protons in their nuclei were likely to be stable, and, furthermore, suggested that a stable element with Z=164 would have a density between 36.0 and 68.4 g/cm3: a range that approaches the expected value for asteroid Polyhymnia.

As their model used the charge distribution in the atomic nucleus as one of its inputs, it could be extended to simulate still more exotic substances including alpha matter: a condensate composed entirely of isolated helium nuclei (alpha particles).

The idea that some asteroids may be composed of materials unknown on Earth is further motivating potential “space miners” who are planning to exploit the precious metals, including gold, that are expected to lie close to the surface of others.

“All super-heavy elements—those that are highly unstable as well as those that are simply unobserved—have been lumped together as ‘unobtainium,’” concludes Rafelski. “The idea that some of these might be stable enough to be obtained from within our solar system is an exciting one.”

Reference

Evan LaForge et al, Superheavy elements and ultradense matter, The European Physical Journal Plus (2023). DOI: 10.1140/epjp/s13360-023-04454-8

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PSI Editor’s note: there are 94 elements in the periodic table which still occur naturally on Earth. Element 93; Neptunium is produced in nuclear reactors. Element 94; Plutonium is produced by bombarding uranium-238 with deuterium nuclei. This first produces neptunium-238 with a half-life of two days, and this decays by beta emission to form element 94. Beyond Plutonium, no heavier elements exist in nature, as they have all decayed into lighter elements.

Some years ago a ‘plataeu of stablility’ was predicted around element 115, but this was before 115 was experimentally recreated in 2003. It has been named Moscovium, and has a half-life of 220 milliseconds.

The physicist Bob Lazar, who claimed to have worked on reverse-engineering an alien spacecraft at Area 51, said the craft was powered by a device using element 115, but no corroborating evidence has ever been made public. If such a plateau of stability was discovered, its existence has been kept secret.

The idea of being able to recreate elements all the way up to 164 seems to me to be not just pushing at the limits of credibility, but rather well beyond credibility, as even if they can be recreated, they will be so unstable, they will decay before they can be observed.

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