An image of dark spots and bright diffuse torches (best seen at the edges). The analysis shows how the combination of heavy elements leaves stains unchanged, increasing the contrast of bright diffuse torches.
Spots on the solar surface appear and disappear over an 11-year cycle. It is driven by a stellar dynamo — the interaction between a magnetic field, convection, and rotation. But we still could not fully understand the physics underlying this mechanism. One of the most striking examples is the Maunder Minimum (17th century), when for as much as 50 years almost all the spots on the solar surface disappeared.
Now the international team managed to find a star that can reveal the details of solar dynamo physics. The object is distant from us for 120 light-years and lives in the territory of Swan. Its surface resembles the sun. There are also correspondences in mass, radius, and age, but in chemical composition there is a cardinal difference. There are about twice as many heavy elements in a star than in ours.
Scientists have combined observations with Kepler and data from ground surveys dating back to 1978. The amazing resemblance to the Sun makes this star a kind of Rosetta stone, contributing to the study of stellar dynamos.
Heavy items make the star more variable
The combination of photometric, spectroscopic and asteroidal information helped to create the most detailed set of observations for a solar cycle like that. The analysis showed that the amplitude of the cycle in the magnetic field of the star is twice as strong as in solar, and the cycle is more visible in visible light. This means that heavier elements create a more powerful cycle. Based on the physical models implemented in the depths of the star’s interior and its atmosphere, the researchers suggested an explanation for a stronger cycle.
First, the heavy elements make the star more opaque, which changes the energy transfer inside the star from radiation to convection. This increases the strength of the dynamo, affecting the amplitude of the variability of the magnetic belt and the pattern of rotation near the surface. Secondly, the heavy elements affect the surface and atmospheric processes of the star. The contrast between the diffuse bright zones (torches) and the quiet solar background increases as the number of heavy elements expands.
Influence of the Sun on Climate
A new study is important, because with its help it is possible to better understand how solar radiation is changing, as well as assess its impact on the Earth’s climate. The greatest attention is paid to the Maunder Minimum, which coincides with the period of cold climate. The analysis will create more accurate constraints for models trying to explain weak activity and a possible reason for the decrease in solar brightness.
