The Sun would contain 55% more silver than previous estimates indicated. This reassessment does not mean that our star contains large amounts of precious metal. Silver remains extremely minor, but its measurement helps trace the chemical history of the Milky Way.
Like other stars, the Sun is composed almost entirely of hydrogen and helium. Heavier elements make up about 1.5% of its mass. Despite their low abundance, they serve as markers for understanding the formation of stars, planets and gas clouds.
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To measure solar silver, astronomers analyze the light produced by the Sun. Atoms present in its atmosphere absorb certain wavelengths. These spectral lines form a characteristic fingerprint, which allows estimating the amount of each element.
The previous assessments relied on simplified models of the solar atmosphere. However, the outer layers of the Sun are crossed by disordered motions, and the omnipresent energy of this environment can also alter the state of the atoms that produced the observed lines.
The new study combines a three-dimensional dynamic model with improved calculations of atomic physics. It notably takes into account non-equilibrium situations, in which silver atoms do not react as in a perfectly stable environment.
With this method, the estimated abundance of silver increases by 55% compared to previous calculations. This result greatly reduces a long-standing discrepancy between the measured composition of the Sun and that of primitive meteorites.
These meteorites formed about 4.6 billion years ago from the same cloud of gas and dust as the Sun. The two values, corrected for the Sun's specific light elements, should therefore have been close. The new estimate makes these compositions much more consistent.
The interest of this work goes beyond the sole composition of our star. Silver and other heavy elements are produced in stars or during stellar explosions. Their distribution allows us to trace the chemical evolution of the Galaxy over generations.
The researchers now wish to apply this method to other stars. Comparing their light signatures could specify when and in which cosmic events silver formed before entering the matter that gave birth to the Solar System.