See the Beauty of an Artificial Solar Eclipse, Created With a First-of-Its-Kind, ‘Perfect’ Satellite Formation
Two satellites’ highly precise alignment allows scientists to study the sun’s outer atmosphere like never before
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One of the ways that scientists study solar wind—charged particles streaming from the sun’s surface—is by observing the sun’s outer atmosphere, called the corona. But because the sun is so blindingly bright, observations of this ethereal region can only be conducted with a telescope attachment called a coronograph—or during a total solar eclipse. To address this issue, a consortium led by the European Space Agency (ESA) decided to create its own solar eclipses.
In December 2024, the agency’s Proba-3 mission launched into space, taking with it two spacecraft: the Coronagraph and the Occulter. In March, the Earth-orbiting satellites flew in “perfect formation,” 492 feet apart from each other, for hours, with one blotting out the surface of the sun from the other’s perspective in a first-of-its-kind feat.
Though the maneuver took place under the watchful gaze of ground control, the satellites aligned and maintained their relative positions, down to a single millimeter, autonomously.
“We almost couldn’t believe our eyes,” Andrei Zhukov, the principal investigator for the Coronagraph’s optical instrument at the Royal Observatory of Belgium, tells the Associated Press’ Marcia Dunn. “This was the first try, and it worked. It was so incredible.”
Besides showing off fancy navigation and positioning technologies, the stunt—which has since been repeated several times—serves to create the world’s first artificial total solar eclipses. The formation places the Occulter spacecraft’s 4.6-foot disk in front of the sun relative to the Coronagraph. The disk then casts a shadow across the Coronagraph’s optical instrument, called ASPIICS (Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun). This allows ASPIICS to image the corona as if during a natural total solar eclipse.
“Our ‘artificial eclipse’ images are comparable with those taken during a natural eclipse. The difference is that we can create our eclipse once every 19.6-hour orbit, while total solar eclipses only occur naturally around once, very rarely twice, a year,” Zhukov explains in an ESA statement. “On top of that, natural total eclipses only last a few minutes, while Proba-3 can hold its artificial eclipse for up to six hours.”
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Coronographs, telescope attachments that block out a star’s glare, could theoretically achieve this same result from the ground. But the problem with Earth-based coronographs is that stray light scattered by our planet’s atmosphere still gets in the way, per Space.com’s Jamie Carter. The Proba-3 mission mitigates this issue by essentially assembling a giant coronograph in space, beyond our atmosphere. From there, ASPIICS can see more details of the corona and make observations almost down to the very edge of the sun’s surface, which was previously only feasible during natural solar eclipses.
“Current coronagraphs are no match for Proba-3,” Jorge Amaya, space weather modeling coordinator at the ESA, says in the statement.
While blocking the sun’s physical light, Proba-3 will hopefully shed metaphorical light on the corona’s mysteries. That includes the “coronal heating problem”—the question of why the corona reaches significantly higher temperatures of around two million degrees Fahrenheit compared to the surface of the sun, which is around 10,000 degrees.
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The mission should also provide insight into a kind of solar activity called coronal mass ejections (CMEs): explosions of plasma and magnetic fields from the sun’s surface. CMEs drive the spectacular aurora borealis but can also endanger communication, power and navigation networks.
Another onboard instrument called the Digital Absolute Radiometer (DARA) will measure how much energy our star is releasing at a specific point in time. Put together with ASPIICS, scientists say these instruments have potential to uncover crucial new information about the sun.
“The first time I saw these pictures, it was difficult to believe,” Damien Galano, a systems engineer at the ESA, tells New Scientist’s Alex Wilkins. “But quickly, it was also a very, very strong feeling of achievement and pride for everything we have done over the years.”
As the Proba-3 mission is still in its commissioning phase, these early images are just a taste of what’s to come. Moving forward, the team aims to lengthen each orbit’s observation time to six hours and to reach full autonomy, without the need for monitoring from the ground.
