La photo la plus proche du soleil

I and the help of the scientific team of the European Space Agency’s Solar Orbiter mission presented the first images of the Sun the closest ever taken. In February 2020, for an unprecedented mission of exploration and study of the Sun of a duration of seven to ten years, our Solar Orbiter aims to make the link between what is happening on the Sun and what is transported by the solar wind, and to provide a deeper understanding of our knowledge of the Sun and its inner heliosphere.

These data, which concern measurements of «variations of the magnetic field, of particles of the solar wind and of images of the surface of the Sun in different wavelengths», were acquired over very limited durations by the planning of the so-called phase of acceptance in flight, and yet the images of the Sun made public today «show details never seen before»! Compared to the images of Nasa’s SDO solar observatory, the images of Solar Orbiter are at least twice as high a resolution.

Once launched, the Solar Orbiter will follow an elliptical path around the Sun, «approaching up to 42 million km» (at this distance, the heat is so intense that no camera can look the Sun in the face), but the two probes do not have the same strategies. The Solar Parker Probe will perform measurements of the outermost part of the solar corona and a little beyond when the heliosphere begins, as for Solar Orbiter will perform UV images of the Sun’s crown with the best spatial resolution ever achieved (70 km/pixel). In addition, Solar Orbiter will also carry out measurements in the solar wind, especially when the Sun Parker Solar Probe and Solar Orbiter are aligned.

As with Solar Parker Probe, Solar Orbiter will obviously not be as close to the Sun as possible. The satellite will bring the Sun closer every five months. At the perihelion, the Solar Orbiter will be just 42 million kilometres from our star, which is closer to the planet Mercury. At the time of maximum approach, when it travels the fastest, the Solar Orbiter will remain for several days roughly positioned above the same region of the atmosphere while the Sun rotates on its axis.

As explained by Anne Pacros, Head of Mission and Scientific Instruments on board the satellite, “these first data are the result of functional tests” which made it possible to verify the operational state of the satellite’s payload and its instruments. 10 of them are divided into two groups and together they provide a holistic view of the Sun and the solar wind: four instruments measuring the plasma characteristics of the solar wind at satellite level and six others responsible for analysing the light emitted by the Sun (remote sensing measurements).

Technically, the images captured exceeded the expectations of scientists and the mission’s requirements in terms of resolution and clarity of images while the satellite is not yet in its final orbit! Currently, Solar Orbiter is located 77 million kilometers from the Sun, or 0.5 Astronomical Unit. As close as possible, the satellite will be only 42 million kilometres from the Sun (0.28 Astronomical Unit), less than a third of the Sun-Earth distance.

There is little doubt that Solar Orbiter will help scientists answer many fundamental questions about how the Sun works. Among the questions most pressing the scientists, let us quote the

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