These three colored disks, published by the European Space Agency (ESA), on November 20 – with a fourth with more explosive contours – are photographs of the Sun taken by the Solar Orbiter probe, on March 22, 2023. Each one is a set of 25 images taken by the probe, then 74 million kilometers from the star. The orange ball, a classic visible light photograph, reveals the gaseous surface whose temperature ranges between 4,500°C and 6,000°C. The spots are colder regions.
The greenish disk is a kind of planisphere of the Sun’s magnetic field. This magnetogram shows that this field is concentrated in the spots regions and is oriented outwards (in red) or inwards (in blue). The same camera can record the movements of matter on the surface of the Sun (third disk), in blue when the matter approaches the lens and in red when it moves away from it. This tachogram reveals that plasma is pushed outward around sunspots. These photographs, of unrivaled quality, can be dramatically enlarged on the ESA website.
The fourth photograph presented in this publication is that of the solar corona. This glowing outer atmosphere lies above the photosphere, the visible surface of the Sun. It was imaged by the space probe’s Extreme Ultraviolet Imager instrument. This 1 million degree plasma follows magnetic field lines that extend from the Sun and often connect neighboring sunspots.
8,000 pixels in diameter
The quality of the images thus collected allows us to observe details of the surface of our star. The ESA specifies in its press release that, in its mosaics of 25 photographs, the solar disk has a diameter of almost 8,000 pixels.
With a total cost of 1.5 billion euros, the Solar Orbiter mission, piloted by the European agency and with which NASA is associated, took off in February 2020. By progressively abandoning the plane of the ecliptic, the one in which the planets evolve around the Earth, Sol, will be the first probe to photograph the poles of the daytime star.
The plane in which Solar Orbiter orbits the Sun will therefore be inclined in 2027 by 24 degrees with respect to the ecliptic, and up to 33 degrees in 2030. To resist heat, a shield designed to withstand a maximum temperature of 520°C It protects the probe and each of its ten measuring instruments or cameras is equipped with windows that only open when in operation.
