On November 20, 2024, the Solar Orbiter mission, a collaboration between the European Space Agency (ESA) and NASA, released four spectacular high-resolution images of the Sun. These images were obtained using the Polarimetric and Helioseismic Imager (PHI) and the Extreme Ultraviolet Imager (EUI), showcasing the Sun's visible surface (photosphere) in unprecedented detail.
The PHI instrument not only captures images in visible light but also measures the magnetic field direction and maps the velocity and direction of various surface movements. These photospheric measurements can be directly compared with a new image of the Sun's outer atmosphere (corona) captured by the EUI on the same day, March 22, 2023.
Daniel Müller, Project Scientist of Solar Orbiter, emphasized the importance of understanding the Sun's magnetic field, stating, "These new high-resolution maps from the PHI instrument reveal the beauty of the Sun's surface magnetic field and its flows in great detail. They are essential for deducing the magnetic field in the Sun's hot corona, which our EUI instrument is reproducing."
The detailed visible light image from PHI reveals the Sun's surface as a continuously moving, incandescent plasma, with temperatures ranging from 4500 to 6000°C. Below this layer, hot, dense plasma churns in the Sun's convective zone, similar to magma in Earth's mantle, resulting in a granular appearance.
Notably, sunspots appear as dark patches on the otherwise smooth surface, indicating regions where the Sun's magnetic field disrupts plasma convection. Consequently, sunspots are cooler and emit less light than their surroundings.
The second image provides a magnetic map of the Sun, the third shows surface movement, and the final image depicts the Sun in ultraviolet light. These images were taken when the Solar Orbiter was less than 74 million kilometers from the Sun, and each high-resolution image covered only a small portion of the Sun, requiring the spacecraft to tilt and rotate to capture the entire solar disk, which was then stitched together into a mosaic.