The clearest image of the Sun’s surface

On November 20, the European Space Agency (ESA) shared four photos of the Solar Orbiter spacecraft taken last March, when the ship was 74 million km from the Sun. These images capture in detail the Sun’s rough surface called the photosphere, the layer that emits the light we see.

The Polarimeter and Solar Seismic Imager (PHI), one of six instruments on board, captures particles scattered across the surface. They are large, chaotic plasma drives, each spanning about 1,000 km. They are created by convection, the process by which hot plasma rises from below and cooler plasma sinks from above, similar to bubbles forming and rising in a pot of boiling water. These foci cover the entire surface of the Sun, except for sunspots, cooler, darker areas that appear like pimples on a smooth photosphere.

The image below is a new map of the Sun’s magnetic field, also from PHI. It revealed that the magnetic field was particularly strong and concentrated in the sunspot area. This helps explain why the sunspot is cooler than its surroundings. The extremely strong magnetic field there limits the plasma’s normal convection process, forcing matter to move with the magnetic field. As a result, some of the heat cannot reach the surface, making the sunspot cooler than other places on the Sun’s surface, according to Daniel Müller, ESA’s Solar Orbiter project scientist.

Another new map called a tachogram shows the speed and direction at which material on the Sun’s surface moves. The blue area moves toward the Solar Orbiter while the red area moves away from the ship, revealing the Sun’s rotation around its axis. Solar wind escaping from the outer atmosphere called the corona was also imaged last March using the Extreme Ultraviolet Imager (EUI) instrument aboard Solar Orbiter.

The Solar Orbiter is currently 120 million km from the Sun, outside the orbit of Venus. Along with NASA’s Parker probe, the probe recently provided new clues about the process by which the solar wind heats up and accelerates to incredible speeds in space. The probe launched in 2020 as part of a joint European-NASA mission to collect never-before-seen images of the Sun’s poles. In early 2025, the spacecraft’s orbit will allow it to reach a higher angle and directly observe the Sun’s poles.