Researchers at Uppsala University have determined that the Sun contains 55% more silver than previous calculations suggested. Their latest estimates are based on more realistic models of the solar atmosphere and help resolve long-standing discrepancies in measured amounts of silver across the solar system.
The Sun, like most stars, is made almost entirely of hydrogen and helium. Heavier elements such as carbon, iron, and silver account for only 1.5 percent of its mass. These elements, even in such small amounts, are extremely valuable to astronomers because they preserve clues about the history and chemical development of the universe.
PhD project reveals solar surprise
“The Sun is one of the key reference points in astronomy, so new knowledge about its composition is important for understanding other stars, planets and cosmic matter,” says Sema Kaliskan, who conducted the study while a doctoral student at Uppsala University’s Department of Physics and Astronomy.
Heavy elements are produced inside stars and during star explosions. They are later incorporated into new stars, planets, and other cosmic matter. Measuring how much of each element is present helps scientists track the chemical evolution of the Milky Way.
Reading silver fingerprints in sunlight
To measure the sun’s silver content, researchers studied sunlight using spectroscopy. Atoms in the sun’s atmosphere absorb specific wavelengths of light, leaving dark features in the spectrum called spectral lines. Each element creates its own unique set of lines, similar to a fingerprint.
Scientists compare these patterns to models of the sun’s atmosphere to calculate how much of an element is present. Previous estimates relied on simplified models. In the new study, the team developed a more advanced approach that produced a 55 percent higher silver estimate than previously.
The researchers combined dynamic models of the sun’s outer layers with improved calculations in nuclear physics. This allows them to more precisely explain how silver atoms interact with light and surrounding particles. Unlike the previous method, the new calculation also takes into account non-equilibrium effects. In this case, the light itself affects the same silver atoms that are responsible for producing the dark absorption lines.
Solving the silver shortage problem in the solar system
“Using our new model, we were able to more accurately interpret the spectral lines used to determine the abundance of solar silver,” says Sema Kaliskan. She began her doctoral research studying the structure of atoms and later applied that expertise to problems in stellar astrophysics.
The revised results address long-standing questions regarding silver in the solar system. Previous measurements suggested that the Sun contains significantly less silver than chemically primitive meteorites. The sun and its meteorites formed from the same cloud of gas and dust about 4.6 billion years ago, so the differences have been difficult to explain.
New calculations bring the abundance of silver in the Sun much more in line with the amounts found in these ancient meteorites.
Follow the silver across the Milky Way
The discovery could also advance scientists’ understanding of how silver and other heavy elements form in stars and stellar explosions before becoming part of later generations of stars and planets. The researchers now plan to use the same method to study other stars.
“By studying the light of stars of different types and ages, we hope to understand where in the universe silver formed and how it was distributed across the Milky Way over time,” Sema Kalliskan said.
About research
The calculations were performed using the Swedish supercomputer Tetralith at the National Supercomputer Center at Linköping University. This project combined expertise in stellar physics and atomic modeling.
Although similar methods have been used before to study other elements, this is the first time this approach has been applied to silver in the sun.
