Variable sunshine— researchers explain why our Sun’s brightness fluctuates

Sunspots [image credit: NASA]

One of the authors of the research says: “The results of our study show us that we have identified the governing parameters in our model”. Both climate and exoplanet research could benefit from the findings.

The Sun shines from the heavens, seemingly calm and unvarying. In fact, it doesn’t always shine with uniform brightness, but shows dimmings and brightenings, reports Phys.org.

Two phenomena alone are responsible for these fluctuations: the magnetic fields on the visible surface and gigantic plasma currents, bubbling up from the star’s interior.

A team headed by the Max Planck Institute for Solar System Research in Göttingen reports this result in today’s issue of Nature Astronomy. For the first time, the scientists have managed to reconstruct fluctuations in brightness on all time scales observed to date – from minutes up to decades.

These new insights are not only important for climate research, but can also be applied to distant stars. And they may simplify the future search for exoplanets.

When an exoplanet transits in front of its parent star, the star darkens briefly. Even from a distance of many light-years, space telescopes register these changes – and thus detect the exoplanets. In theory. In practice, it’s more complicated, as the brightness of many stars fluctuates, similar to that of the Sun.

These fluctuations can overlay the signals of passing exoplanets. “However, if we are aware of the details of the star’s intrinsic brightness fluctuations, exoplanets can be detected with great precision,” says Alexander Shapiro of the Max Planck Institute for Solar System Research.

Shapiro and his colleagues have taken a first step in this direction with their current paper – with a detailed look at a special star: our Sun. Since the beginning of the space age, numerous spacecraft have delivered detailed data collected unaffected by the disturbances caused by the Earth’s atmosphere.

These data seriously challenge any model describing fluctuations in stellar brightness: can the measured fluctuations be reconstructed using a model? And is it possible to link the fluctuations to the physical properties of the star?

Continued here.