Some asteroids in our solar system are so dense that no element on Earth can explain their properties. Instead, a new study suggests that they may consist of naturally occurring “superheavy elements” other than those listed in the periodic table (our best available catalog of 118 chemical elements).

“If asteroids contain superheavy elements, it will raise many questions about how these elements form and why we have not yet discovered them outside of asteroids,” said study co-author Johann Rafelski, a professor of physics at the University of Arizona. . Living science.

Extremely heavy space rocks, known as compact ultradense objects (CUDOs), are generally heavier than osmium, the heaviest naturally occurring element on Earth. One such rock is 33 Polyhymnia, located in the main asteroid belt between Mars and Jupiter. Scientists have long been puzzled by its density because the 34-mile-wide (55 kilometers) object does not have the mass necessary to compress minerals into superdense forms. However, due to its small size and distance from Earth, its composition was difficult to determine.

Previous studies had suggested that the density of CUDOs like 33 Polyhymnia could be explained if the objects were filled with mysterious dark matter particles, which can be found in clusters inside asteroids, rather than as freely dispersed particles. Now, in a study published September 15 in The European Physical Journal Plus, Rafelski and two colleagues have shown mathematically that the existence of CUDO can be explained not by dark matter but by unknown classes of chemical elements that are much denser outside the periodic table. than osmium.

Scientists have long debated whether elements heavier than oganesson, the last in Mendeleev’s table, can be found in nature and be stable. Such superheavy elements are highly radioactive and decay within milliseconds due to the repulsion of large numbers of protons packed in their nuclei.

Previous work had suggested that a theoretical region of superheavy elements around atomic number 164 existed in the Mendeleev table, called an “island of stability.” At this weight, elements could not undergo rapid radioactive decay and would exist for short periods of time. Rafelski and his team’s new calculations are consistent with this prediction.

“All superheavy elements—both highly unstable and simply unobserved ones—are combined in ‘unobtaium’,” Rafelski said in a statement. “The idea that some of them might be stable enough to be removed from our solar system is exciting.”

To reach their conclusions, the researchers theorized the atomic structure of hypothetical superheavy elements using a rough model of the atom known as the Thomas-Fermi model. They found that elements with atomic numbers around 164 would have densities ranging from 36 to 68.4 grams per cubic centimeter (20 to 39.5 ounces per cubic inch).

“What’s particularly exciting about this study is that we don’t know exactly where this will lead,” Rafelsky told Live Science.