The solar eclipse on August 12 will allow researchers to test their understanding of the solar corona using observational data from ESA’s Solar Orbiter. 

• Observation campaign: In the days leading up to the solar eclipse on August 12, 2026, ESA’s Solar Orbiter spacecraft will peer at the Sun as part of a special campaign.
• Calculations: Observational data from Solar Orbiter’s SO/PHI telescope serve as the starting point for modeling the structure and dynamics of the solar corona.
• Stress test: During a solar eclipse, the corona is clearly visible, even without special instrumentation. The event offers an exceptional opportunity to test the model calculations. 
• Solar activity: Solar wind and solar flares originate in the corona. Researchers therefore try to better understand the processes in this layer of our star.

Every endeavor to understand our star’s turbulent nature must take into account the solar corona. There, in the Sun’s hot atmosphere, many dynamic processes originate: The solar wind, the never-ending stream of charged particles from the Sun, is accelerated and rushes out into space from the corona; violent particle and radiation eruptions draw their explosive energy from there. In order to understand how the complex interplay of plasma heated to temperatures of more than one million degrees, strong magnetic fields, and waves drives these phenomena, researchers develop theoretical models and simulate the processes in the corona on computers.

Such calculations are based on observations of the magnetic field at the Sun’s visible surface, known as the photosphere. Instruments such as SO/PHI (Polarimetric and Helioseismic Imager) on board ESA’s Solar Orbiter spacecraft routinely provide such data. SO/PHI was developed and built under the leadership of the Max Planck Institute for Solar System Research (MPS) and is operated by MPS.

To verify whether the models realistically describe the processes in the corona, in a second step the results must be compared with observations of the Sun’s atmosphere. As the photosphere outshines the much fainter corona, the latter can only be made visible using special instruments called coronagraphs. In this process, an occulting device blocks the solar disk, allowing the delicate structures of the corona to be seen. The same thing happens naturally during a solar eclipse: the Moon, acting as an occulting device, moves in front of the solar disk.

Researchers at the MPS and the US based research company Predictive Science Inc. (PSI) are therefore now looking to the upcoming solar eclipse on August 12.

However, in their efforts to model the Sun’s atmosphere, researchers face a problem: the input data from the photosphere are never entirely up to date. This is because observations typically come from along the Earth-Sun line, both from space probes and ground-based telescopes alike, yielding a very limited view of our star. Only the side of the Sun facing Earth is visible. In order to “feed” the models with information about the magnetic fields across the Sun’s entire surface, researchers must wait for a complete solar rotation of approximately 27 days — and can then only calculate an image of the corona averaged over this period.

Only Solar Orbiter can remedy this situation. Unlike other solar probes, it orbits the Sun and is currently leaving the far side of our star. SO/PHI can therefore determine the magnetic field on that side, while probes near Earth simultaneously observe the Sun’s near side – thus compiling a complete picture of the Sun’s photosphere much more quickly, in this way significantly improving the numerical modelling of the corona.

As part of the current observation campaign leading up to the solar eclipse, SO/PHI has already begun collecting data. Working closely with ESA, the MPS team ensures that the data are transmitted to Earth as quickly as possible and processed for further scientific use. This allows researchers at PSI to model the corona as promptly as possible, predict its appearance at the time of the solar eclipse — and then compare their results with images of the corona taken on August 12. This collaboration had already proven successful during the solar eclipse of April 8, 2024, which was primarily visible in the United States. Joint findings were published in the journal Science.

The upcoming solar eclipse on Wednesday, August 12, will be visible as a total solar eclipse in Greenland, Iceland, Spain, and a small part of Northern Portugal. In other parts of Europe, such as Germany, a partial solar eclipse will be visible. As seen from Göttingen, the Moon will cover almost 90 percent of the Sun. As the solar eclipse begins in the evening, the Sun will no longer be high in the sky at that time. While still a breathtaking show, the relatively small part of the Sun that is not covered by the Moon will unfortunately blend the fine structure of the corona but, more importantly, can severely damage your eyes if watched unprotected: please, do wear proper eclipse glasses!

The Solar Orbiter mission is an ESA-led project of ESA and NASA. The spacecraft was launched into space in February 2020. Since then, it has been orbiting the Sun in highly elongated elliptical orbits. It is equipped with a total of ten scientific instruments. The MPS contributed to four of these instruments.