Back to the story of SRON 
Sheer powers of the sun
1980
The 1960s… Using the first X-ray instruments mounted in the nose cones of sounding rockets, space researchers in Utrecht discovered that the Sun has a corona with a temperature of millions of degrees.
Then, in 1972, their experiments on the TD-1A satellite allowed for longer-term observations. And much more stable ones. They discovered that solar flares emit X-rays in short, intense flashes, known as ‘elementary bursts’...
In 1980, as the Sun was once again going through its eleven-year active cycle, a new Utrecht-developed instrument was carried aboard NASA’s Solar Maximum Mission: the X-ray imager HXIS.
This taught us how solar flares arise when magnetic field lines suddenly form loops. HXIS observed the footpoints of these loops glowing brightly on the Sun, acting as point contacts for an electric current of billions of amperes.
The current heats the gas within the loop, triggering the emission of X-rays. The gas can reach temperatures of up to 40 million degrees. One example is the widely studied ‘Queen’s Flare’ on 30 April 1980, the day Queen Beatrix was crowned. As the hot gas expands, the loop rises until it ‘snaps’. And voilà: a solar flare.
Dutch space research owes much of its new knowledge and experience to the world-renowned solar research carried out in Utrecht. However, following SolarMAX, the focus of the space laboratories shifts towards X-ray and infrared astronomy of phenomena outside our solar system. Other missions however, continue to uncover new secrets of the Sun.
- Photos, credit NASA: A solar flare; Magnetic fields on the Sun; An astronaut (bottom right) attempts to retrieve SolarMAX from the air using a robotic arm; Astronauts carrying out a spacewalk. The first satellite repair in space has been successfully completed.
- Article about SolarMAX in the Leeuwarder Courant, available to read in the Delpher newspaper archive.