SOHO celebrates its 22nd year around the Sun


The Solar and Heliospheric Observatory (SOHO) celebrates 22 years of observing the Sun, marking a complete magnetic cycle in the life of our star. Its mission is to study the internal structure of the Sun, its external atmosphere and the origin of the solar wind.

On December 22nd, the Solar and Heliospheric Observatory (SOHO) celebrated its 22 years in space. A significant milestone, which corresponds to the average duration of the total magnetic cycle of our star. Sunspot cycles are known to occur every 11 years, but the complete cycle is twice this length due to the behavior of magnetic fields. The polarity of the sun changes gradually through its cycle, so that after 11 years the orientation of the field will have switched between the northern and southern hemispheres. At the end of a 22-year cycle, the orientation of the magnetic field is the same as at the beginning.

SOHO is a real success. Launched in 1995, the mission was to last only three years. But it is still relevant ongoing and relevant today. SOHO’s 22 years of observation will have inflated our space weather prediction capability, which affects our modern technologies. Space communications, broadcasting, weather services and navigation are all affected by space weather. The same is true for energy distribution and terrestrial communications, especially at northern latitudes. Solar weather can also degrade not only the performance but also the lifespan of communication satellites.


The Sun’s magnetic field operates over a 22-year cycle. It takes 11 years for the field orientation to shift between the northern hemisphere and the southern hemisphere, and another 11 years to return to its original orientation. This image is composed of snapshots of the Sun taken with the Extreme Ultraviolet Imaging telescope installed on SOHO. Image: SOHO (ESA and NASA)

In addition to improving our ability to predict space weather, SOHO has made other important discoveries. After 40 years of research, SOHO finally found evidence of seismic waves in the Sun. Called g-modes, these waves revealed that the heart of the Sun rotates 4 times faster than the surface. SOHO was also the privileged witness of the passage of comets near the Sun – more than 3,000 – although the study of comets does not form part of its attributions. But why not? Comets are indeed primitive relics of our solar system. Observing them allows us to learn more about our history.

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SOHO continues to turn its eye on the Sun from its location, located about 1.5 million kilometers from the Earth. Its orbit is adjusted to be able to communicate clearly with the Earth without interference from the Sun.

Carl Frantz

Polyglot, humanitarian, Carl was born in Germany but raised in the USA. He writes mostly on tech, science and culture.