Scientists used Solar Orbiter’s EUI camera in a new mode of operation to record a portion of the sun’s atmosphere at extreme ultraviolet wavelengths that had been nearly impossible to image until now. This new mode of operation was made possible by a last-minute camera “hack” and is sure to influence new solar instruments for future missions.
Solar Orbiter’s Extreme Ultraviolet Imager (EUI) returns high-resolution images of structures in the Sun’s atmosphere. Scientists call this area the corona. During construction of the EUI, a last-minute modification of the safety door on the front of the device allowed the target area to be viewed deeper than originally specified.
“It was a real breakthrough,” says Frédéric Ocher, of the Institute of Astrophysics at the University of Paris-Sud, and a member of the EUI team. “I had the idea of doing this and seeing if it would work. It’s actually a very simple modification to the tool.
This involved adding a small, protruding “thumb,” weighing a few grams, to the door of the machine. When the door slides away to let light into the camera, if stopped halfway, the thumb covers the sun’s bright disk, and the EUI can detect a million times fainter ultraviolet light coming from the surrounding corona.
The team refers to this as the fuzzy operating mode. Testing with the mysterious EUI has been going on since 2021. Now the team is confident that it will work and it has worked Written paper She published a video clip explaining the results.
The movie shows an ultraviolet image of the Sun’s corona taken with the EUI occultator. An ultraviolet image of the Sun’s disk is superimposed in the center, in the area left blank by the occultation. The image of the sun’s disk was taken by NASA’s STEREO mission, which happened to be looking at the sun from roughly the same direction as Solar Orbiter at the same time, so the features on the surface have a good correlation to features on the corona.
In the past, images of the sun’s corona were taken with specialized instruments called coronagraphs. For example, the coronagraph of the Solar Orbiter is called Metis. The value of this new approach is that the chronograph and camera can be included in the same instrument.
“We have shown that this works so well that you can now think about a new type of instrument that can image the Sun and its corona,” says Daniel Müller, ESA’s Solar Orbiter project scientist.
Even before these new tools, there is a lot of new science coming from EUI. The occult mode allows scientists to see deeper into the sun’s atmosphere. This is the area that lies outside the field of view of classical UV imagers but is usually obscured by conventional coronagraphs. However, now, EUI’s mysterious instrument can easily image this little-explored area.
“The physics are changing there, the magnetic structures are changing there, and we haven’t gotten a close look at them before. There must be some secrets that we can find out now,” says David Bergmans, Royal Observatory of Belgium, and principal investigator at EUI.
Solar Orbiter is an international cooperation space mission between ESA and NASA, managed by the European Space Agency.
Notes to editors:
Beyond the disk: Ultraviolet corona imaging observations from the extreme ultraviolet imager aboard the Solar Orbiter. By F. Osher et al Published in Astronomy and astrophysics Volume 674, June 2023.
For more information please contact:
ESA Media Relations
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