For centuries, the search for new elements has been the driving force behind many scientific disciplines. Understanding the structure of the atom and the development of nuclear science allowed scientists to achieve the old goal of alchemists: to transform one element into another. Over the past few decades, scientists from the United States, Germany and Russia have figured out how to use special tools to fuse two atomic nuclei and create new, superheavy elements.

These heavy elements are generally unstable. Heavier elements have more protons, or positively charged particles, in their nuclei; Some protons scientists have created have numbers as high as 118. With so many protons, the electromagnetic repulsive forces between protons in the atomic nucleus outweigh the attractive nuclear force that holds the nucleus together. Scientists have long predicted that elements with about 164 protons might have relatively long half-lives and even be stable. They call this place the “island of stability”; The attractive nuclear force here is strong enough to balance any electromagnetic repulsion.

Because heavy elements are difficult to produce in the laboratory, physicists like me search for these elements everywhere, even beyond Earth. To narrow down the search, we need to know what natural processes can produce these elements. We also need to know what properties they have, such as their mass density.

Density calculation

From the beginning, my team wanted to determine the mass density of these superheavy elements. This property can tell us more about how the atomic nuclei of these elements behave. Once we have an idea of ​​their density, we can better understand where these elements may be hiding.

To determine the mass density and other chemical properties of these elements, my research group used a model that represents an atom of each of these heavy elements as a single charged cloud. This model works well for large atoms, especially metals arranged in a lattice structure.

We first applied this model to atoms of known density and calculated their chemical properties. Once we realized it worked, we used the model to calculate the density of elements with 164 protons and other elements in this island of stability.

According to our calculations, we expect the densities of stable metals with atomic numbers around 164 to be between 36 and 68 g/cm3 (21-39 oz/in3). However, we used a conservative assumption about the mass of the atomic nucleus in our calculations. It is possible that the actual range is 40% higher.

Asteroids and heavy elements

Many scientists think that gold and other heavy metals settled on the Earth’s surface after asteroids hit the planet. The same thing could happen to these superheavy elements, but the superheavy, dense superheavy elements sink into the ground and are removed from the Earth’s surface through the subduction of tectonic plates. However, although researchers have not found superheavy elements on the Earth’s surface, they may be present in asteroids similar to the asteroids that may have brought them to this planet.

Scientists estimate that the mass density of some asteroids exceeds the mass density of osmium (22.59 g/cm3, 13.06 oz/in3), the densest element found on Earth. The largest of these objects is asteroid 33, nicknamed Polyhymnia, with an estimated density of 75.3 g/cm3 (43.5 oz/in3). However, since it is very difficult to measure the mass and volume of distant asteroids, this density may not be completely accurate.

Polyhymnia isn’t the only dense asteroid. In fact, there are a number of superheavy objects, including asteroids, that may contain these superheavy elements. A while ago I named this class Compact Ultra-Dense Objects, or CUDO.

In a study published in the European Physical Journal Plus in October 2023, my team proposed that some CUDOs orbiting the Solar System may still contain some of these dense, heavy elements in their cores. Their surfaces will eventually accumulate ordinary matter and appear normal to a distant observer.

So how are these heavy elements produced? Some extreme astronomical events, such as the merger of binary stars, can be hot and dense enough to form stable superheavy elements. Some of the superheavy material may remain in the asteroids formed in these events. They can become trapped inside these asteroids that orbit the solar system for billions of years.

looking to the future

The European Space Agency’s Gaia mission aims to create the largest and most accurate 3D map of the entire sky. Researchers can use these highly accurate results to study the motion of asteroids and determine which ones might be unusually dense.

Space missions are conducted to collect material from the surface of asteroids and analyze them on Earth. Both NASA and Japan’s national space agency JAXA have successfully targeted low-density near-Earth asteroids. Just this month, NASA’s OSIRIS-REx mission returned an example. Although analysis of the samples is just beginning, there is a small chance that they contain dust containing superheavy elements that have accumulated over billions of years.

A single sample of dust and rock sent to Earth would be sufficient. NASA’s Psyche mission, set to launch in October 2023, will fly to and sample a metal-rich asteroid that is more likely to host superheavy elements. More asteroid missions like this will help scientists better understand the properties of asteroids orbiting the Solar System.