There is a gap in our observations of the Sun: Part of its atmosphere is virtually invisible to our telescopes. But images taken from Earth during a solar eclipse fill this hole, providing an unprecedented look into the hidden layer of our star.
But capturing these images requires expertise, special equipment and a lot of patience. . One of the few who can receive and process solar eclipse images Czech mathematician will reveal some of the sun’s best-kept secrets Miloslav Druckmüller. The breathtaking renditions of the wispy, white rays and looping magnetic lines that make up the solar corona emerging from the eclipsed sun to the human eye are well known in solar physics circles.
Druckmüller spoke to Space.com from his office at Brno University of Technology in the Czech Republic, a few days before leaving for Mexico. There, in collaboration with researchers from the University of Hawaii, he will oversee a complex imaging campaign during the research. Total solar eclipse on April 8.
Relating to: How to photograph the total solar eclipse on April 8, 2024?
On the day of the eclipse, 66 cameras equipped with special filters and distributed at three observation points in Mexico and the United States will capture tens of thousands of images during the approximately four-minute eclipse. The researchers hope that Druckmüller’s specialist image processing technology can reveal some previously unknown information about the normally invisible region of the sun from this huge data set.
Blind spot
The solar corona, composed of extremely thin charged gas called plasma, is the upper part of the Sun. atmosphere of the sun. It is a million times dimmer than the underlying photosphere that forms the Sun’s visible surface, so it is completely eclipsed by the star’s light when viewed in visible light.
To observe the corona, astronomers need to obscure the visible solar disk to allow faint coronal light to appear in the dark universe. To do this, they use a tool called . coronagraphIt is equipped with an occulter that blocks sunlight.
However, if the oculator only covers what is visible sunDiffraction (the bending of light around an obstacle) causes the bright light of the photosphere to spread to the edges of the oculator, distorting photographs. For this reason, astronomers use larger oculators that also cover the inner corona to a distance of one solar radius from the sun’s surface.
However, while the moon is far away and does not cause any diffraction, it is just the right size to perfectly cover the sun’s disk during a total eclipse.
“Any coronagraph that attempts to imitate a solar eclipse is vastly inferior to a real solar eclipse,” Druckmüller said. “It’s very close to the telescope, which means it causes diffraction. Therefore, the occulter must be much larger than the solar disk, which means we can’t see the innermost part of the corona.”
Because of these limitations, scientists know very little about the processes taking place in this hidden region.
“If you take images from space telescopes Solar Dynamics Observatory“You can see a small part of the corona,” Shadia Habbal, professor of solar physics at the University of Hawaii and Druckmüller collaborator, told a conference in Brno in November 2022. “It is reflected towards the surface, but this is clearly not enough to understand how this plasma is expanding into space.”
Corona is the source of this solar wind, a steady stream of charged particles expanding throughout the solar system. Sometimes it erupts with huge explosions. coronal mass breakthroughsIt can cause dramatic geomagnetic storms on Earth. Most of the processes that accelerate this solar wind into space occur in the blind spot of the coronagraph: the Sun.
A serendipitous discovery
In Druckmüller’s solar eclipse images, this hidden region is revealed in unprecedented detail. Coronal gas, composed mostly of ionized hydrogen and helium with small amounts of heavier elements such as iron, magnesium, silicon or calcium, orbits the sun’s magnetic field lines. Elsewhere, it flows into space from large sunspots, or active regions, and flows through coronal holes where magnetic field lines break.
Druckmüller first tried solar eclipse photography in 1999; For the first time in 150 years, the moon’s shadow visited Central Europe. The Czech Republic was just outside the totality band and stormy weather threatened to ruin the experience at many of the closest viewing locations. Druckmüller set out for Hungary, which provided “perfectly clear skies”.
Druckmüller, an expert in mathematical image analysis, spent months perfecting the photographs; He attempted to create images that mimic what a human observer would experience if their eyes could handle the enormous difference in brightness between the parts of the corona near the sun’s surface. more removed. He had no idea at the time that this newfound “hobby” would turn into a second career.
“I was just playing with it,” Druckmüller said. “My goal was to create beautiful, high-quality solar eclipse images. That’s it.”
In the early 2000s, he shared his creations on a personal website. From there, one of the images found its way into Habbal and colleagues’ paper published in a scientific journal. He didn’t know they were using his picture and they didn’t know it was his.
“It was a complete coincidence,” Druckmüller said. “Someone took it from my website and copyrighted it. I discovered this through a friend. I contacted them to work it out and we started collaborating. Within a year, we were on an expedition together.”
temperature measurement
Druckmüller has participated in more than a dozen solar eclipse observations since 1999. Over the years, campaigns have become more complex. For the upcoming eclipse, Druckmüller’s team in Brno sent thousands of pounds of special photographic equipment to be spread across three observation points.
In addition to capturing the white light of the corona, researchers can now visualize the spectral lines of various energetic ions present in the coronal gas. This opens the door to more exciting science.
“Different ion species appear at different temperatures, so by imaging the spectral lines of different ion species we can measure the temperature in different parts of the corona,” Druckmüller said. said. “This is very difficult to do outside the visible part of the spectrum and cannot be done by probes in space that do not actually see visible light.”
Druckmüller admitted that the increasing complexity of the observations took some of the fun out of the experience. What was once an exciting adventure now looks more like an industrial operation.
Related Stories
—Scientists may have solved the sun’s biggest mystery
—Scientists are finally looking inside the sun’s central corona
—See amazing new sun photos from the world’s largest solar telescope
“We will spend four days putting all the equipment together,” he said. “The eclipse itself is really stressful for us because everything has to go right. I’ll be relieved when I get back to my office and find the hard drive on my desk to work on.”
Druckmüller hopes to have the first images ready to share with the world and scientists in Hawaii two weeks after the eclipse. He said it may take until the next expedition to process all the data.