For several years now, astronomers who study the sun have faced a little mystery — our star seemed to hold too little silver. Whenever scientists examined the sun's outer layers, they've seen significantly less silver than they've expected to find.
Where, then, did the missing silver go?
As it turns out, this mystery may finally be solved. Newly published research suggests that the sun's missing silver may have been hiding in plain sight all along.
At first, the real mystery might seem to be why you'd seek silver in the sun at all. After all, 98.5% of the sun's mass is made from lightweight hydrogen and helium. Silver is just a tiny fraction of the remaining 1.5%, which also includes traces of other heavy elements like iron and copper.
These trace elements can illuminate the history of the cosmos. Silver is thought to form when dying stars violently explode in supernovas. When astronomers find silver in the sun and other stars, they can retrace the silver's origins and how stars have evolved over the eons.
"By studying the light of stars of different types and ages, we hope to understand where silver is formed in the universe, and how it has been distributed throughout the Milky Way over time," says Sema Caliskan, the lead author of the research and now a postdoc at the University of Liège in Belgium, in a statement.
Silver is particularly interesting because it's also found in utterly ancient meteorites called CI chondrites. These meteorites formed from the same primordial matter that created the sun, 4.6 billion years ago. As a result, when scientists break into CI chondrites that have fallen to Earth, they expect to find silver levels that match those they see in the sun.
Astronomers can measure the latter from afar by looking at sunlight's spectral lines. As light streams out from the sun's heart, it crashes into the atoms of our star's outer layers, which absorb the light at certain wavelengths. Look at a spectrum of sunlight, and you'll see dark lines where light has been absorbed. Atoms of different elements absorb different wavelengths, so each element leaves a distinct fingerprint.
Scientists can pore over these spectral fingerprints to reconstruct what elements created them and in what quantities. Therein lies the mystery: The sun seemed to contain much less silver than CI chondrites would indicate. This missing silver is a source for confusion in the sun's history.
Caliskan and her colleagues wondered if astronomers were missing something. They could not visit the sun in person, but they could still find where the silver might be hidden by simulating the sun's atoms on a computer. If they could create a high-silver model that still spawned the low-silver spectral lines, that model could be a good guess for the silver's whereabouts.
Other scientists had tried this before to limited success, but their simulations had been relatively simple. As light strikes an atom, the light has all sorts of intricate effects on the atom's innards. These effects can alter how the atom absorbs the light and, therefore, change how astronomers see that light.
Past models hadn't accounted for many of these tricky "non-equilibrium effects", because simulating them is far easier said than done. They're messy and complex and they vary a great deal from atom to atom.
In fact, no known scientists had ever tried to simulate a silver atom with non-equilibrium effects before Caliskan and her fellow investigators took on the challenge. They tried with their best guesses and the power of the Tetralith supercomputer in Linköping, Sweden.
Indeed, these non-equilibrium effects seem to explain the silver mystery. Based on their model, Caliskan and colleagues calculated that the sun holds 55% more silver than astronomers have measured.
This isn't a perfect match for the CI chondrites, but it's close enough that investigators can rule out any extraordinary cause. Instead, the missing silver may have been right there, in the sun all along, simply occluded from astronomers' view by tricks of physics. Next, Caliskan and colleagues plan to use this method to simulate other types of stars.
They published their work in the journal Astronomy & Astrophysics in July 2026.
