The Sun's Hidden Silver: New Solar Abundance Findings

HMI Continuum
Image Credit: Solar Dynamics Observatory / NASA / Scientific Frontline

Scientific Frontline: Extended "At a Glance" Summary: Solar Silver Abundance

The Core Concept: Researchers at Uppsala University have determined that the Sun contains 55 percent more silver than previously estimated, bringing its composition into alignment with chemically primitive meteorites.

Key Distinction/Mechanism: Unlike earlier measurements that relied on simplified assumptions, this updated abundance is derived from a dynamic 3D model of the Sun’s outer layers combined with non-equilibrium atomic physics calculations. This captures how solar light influences the same silver atoms that create dark absorption lines in the spectrum.

Major Frameworks/Components:

• Spectroscopy: The analysis of sunlight to identify dark absorption lines, which act as unique elemental fingerprints in the solar spectrum.
• Dynamical Atmospheric Modeling: The use of advanced 3D simulations of the Sun's outer layers to create a realistic physical environment for calculation.
• Non-Equilibrium Atomic Physics: Calculations (Non-LTE) that account for how radiation and specific particle interactions explicitly impact the atomic states of silver.

Branch of Science: Stellar Astrophysics, Astronomy, and Atomic Physics.

Future Application: The computational methods developed in this study will be applied to other stars of varying types and ages, enabling researchers to map the formation and distribution of heavy elements throughout the Milky Way.

Why It Matters: The Sun serves as astronomy's primary baseline reference. Because heavy elements act as a chemical fossil record, accurately mapping their trace presence in the Sun is fundamental to understanding the evolution of stars, planets, and cosmic material across the universe.

The solar spectrum: The two strongest silver lines, highlighted in white, lie in the ultraviolet region, which is invisible to the human eye.
Image Credit: Anish Amarsi.

Researchers at Uppsala University have calculated that the Sun contains 55% more silver than previously estimated. The results are based on more realistic modeling of the Sun’s atmosphere and resolve a long-standing problem of missing silver in the solar system.

Like most stars, the Sun consists almost entirely of hydrogen and helium, and only 1.5% of its mass consists of heavier elements, such as carbon, iron, or silver. Yet, these trace elements are extremely important. They act as a fossil record of the cosmos.

“The new knowledge about the Sun’s composition is important for the understanding of other stars, planets, and cosmic material, because the Sun is one of astronomy’s key reference points,” says Sema Caliskan, who conducted the work during her PhD studies at the Department of Physics and Astronomy at Uppsala University.

Understanding the Milky Way Heavy elements are formed in stars and during stellar explosions, and they become part of new generations of stars and planets. Mapping the abundance of these elements is key to understanding the chemical evolution of the Milky Way.

To determine the amount of silver in the Sun, the researchers analyzed sunlight using spectroscopy. When atoms in the solar atmosphere absorb light, they produce dark absorption features at specific wavelengths in the spectrum, known as spectral lines. These lines act as fingerprints, with each element producing a unique pattern.

The fingerprint is compared to calculated atmospheric models to quantify the abundance of silver in the Sun. Previous estimates were based on simplified models. However, in this new study, the researchers developed a new model that predicts 55% more silver than before. They combined a dynamical model of the Sun’s outer layers with improved atomic physics calculations to capture how silver atoms interact with light and other particles. Unlike earlier methods, the new calculations include nonequilibrium effects, meaning that the light influences the same silver atoms that create the dark absorption lines.

The Solar System’s Missing Silver “With our new model, we were able to interpret the spectral lines used to determine the solar silver abundance more accurately,” says Sema Caliskan, who started her PhD studies working on the structure of atoms and later applied her expertise to problems in stellar astrophysics.

The new silver value resolves a long-standing problem of missing silver in the solar system. Until now, the silver abundance measured in the Sun was significantly lower than that found in chemically primitive meteorites, even though both the Sun and the meteorites formed at the same time from the same cloud of gas and dust 4.6 billion years ago. The new silver value in the Sun is now in much better agreement with these meteorites.

Method Could Be Used on Other Stars The new results also improve our understanding of how silver and other elements are produced in stars and stellar explosions and later incorporated into new generations of stars and planets. The same method will now be applied to other stars.

“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.

Funding: The study is funded by the Swedish Research Council, the Royal Swedish Academy of Sciences and the Anusandhan National Research Foundation.

Published in journal: Astronomy & Astrophysics

Title: Ag I model atom and the 3D non-LTE solar silver abundance

Authors: S. Caliskan, A. M. Amarsi1, P. Jönsson, N. Grevesse, and B. K. Sahoo

Source/Credit: Uppsala University | Camilla Thulin

Edited by: Scientific Frontline

Reference Number: asph072026_01

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