Using longer exposures and sophisticated processing techniques, scientists took extraordinarily high-reliability photos of the Sun's outer atmosphere - which we call the corona - and discovered fine details that have never been detected before.
The Sun is a complex object, and with the Parker Solar Probe mission about to be launched, we are about to learn much more about it. But there is still a lot we can do with our current technology, as scientists at the Southwest Research Institute (SWRI) have shown.
The team used the COR-2 coronagraph instrument at NASA's Solar and Ground Relations Observatory to study details in the outer atmosphere of the Sun. This instrument takes images of the atmosphere using what is known as a concealment disk - a disk placed in front of the lens which blocks the real Sun from the image and therefore the light that would overload the fine details in the image.
The corona is extremely hot, much warmer than the inner photosphere, reaching 2 million degrees Celsius. It is also the source of the solar wind - the constant flow of charged particles coming out of the Sun in all directions.
"In deep space, the solar wind is turbulent and stormy," says SwRI solar physicist Craig DeForest.
If turbulence was occurring at the source of the solar wind - the Sun - then we should have been able to see complex structures in the crown as its cause, but earlier observations did not show such structures. Instead, they showed the crown as a smooth, laminar structure. Except, as it turned out this time. The structures were there, but we could not get an image resolution high enough to see them.
In order to obtain the images, the research team carried out a special three-day campaign in which the instrument recorded images of different exposure than usual, allowing more time for light from weak sources to be detected by the coronagraph. But that was only part of the process.
While the hidden disk does a great job of filtering the bright light from the Sun, there is still a lot of noise in the resulting images, both around space and the instrument. They have developed new filtering algorithms to separate the corona from the noise and adjust the brightness. And, perhaps more challenging, correct the blur caused by the movement of the solar wind.
Finding out what this phenomenon is may require some extra help from the new Parker probe. Until then, we'll have to wait and wonder how our Sun can be mysterious. The probe will be launched next month. [ ScienceAlert ]