PHI's view of the Sun in visible light

This image shows the Sun in visible light. It was taken by the Polarimetric and Helioseismic Imager (PHI) onboard the Solar Orbiter spacecraft on 22 March 2023. The instrument collected red light with a wavelength of 617 nanometres.

What you see is the visible surface of the Sun, also called the photosphere. Almost all radiation from the Sun comes from this layer, which has a temperature between 4500 and 6000 °C. Beneath it, the hot, dense plasma is churned around in the ‘convection zone’ of the Sun, not unlike magma in Earth's mantle.

The most striking features in this image are the sunspots. These look like dark spots, or holes, in the otherwise smooth surface. Sunspots are regions where the Sun's magnetic field breaks through. This inhibits the plasma’s convection because charged particles are forced to follow the magnetic field rather than following the heat-mixing convective flow. As a result, sunspots are colder than their surroundings and send out less light.

Assembled from multiple high-resolution images taken by the PHI instrument, the diameter of the Sun's disc is spanned by around 8000 pixels. It is one image of a set of four, three being the first high-resolution full-disc views of the Sun from PHI and the fourth an image of the Sun's corona taken by Solar Orbiter's Extreme Ultraviolet Imager (EUI).

Read the full story here