Top line
If you were lucky enough to witness last week’s total solar eclipse, you will have witnessed one of nature’s rarest spectacles – the Sun’s soft white corona glowing around the Moon’s silhouette. It’s a view that has helped transform solar science for generations, including… Proving Albert Einstein right. Now scientists no longer have to wait for the moon to provide them with this opportunity. By flying two spacecraft in extremely precise formation, ESA’s Proba-3 mission is creating an artificial solar eclipse lasting up to five hours at a time, providing an unprecedented view of the corona – with early results revealing new information about the solar wind.
The Sun’s inner corona appears green in this image taken on May 23, 2025 by the ASPIICS coronagraph aboard Proba-3, an ESA formation flyby mission capable of creating a total solar eclipse in orbit. This image, taken in the visible light spectrum, shows the solar corona similar to how the human eye would see it during an eclipse through a green filter. The hair-like structures are detected using a specialized image processing algorithm.
ESA/Proba-3/ASPIICS/WOW algorithm
Basic facts
Usually, the only opportunity to study the Sun’s faint corona comes during a total solar eclipse, when the Moon obscures the Sun’s bright disk. These events occur somewhere on Earth about every 16 months, and their totality rarely lasts longer than a few minutes.
Launched in December 2024, Proba-3 consists of two separate spacecraft that fly in formation with extraordinary precision, maintaining their relative positions to within just a few millimeters at distances of 472 feet (144 metres). Together, the two spacecraft act as one giant chronograph, with one spacecraft carrying a hidden disc that obscures the sun and the other observing the dim corona with a telescope.
Unlike a natural total solar eclipse, which typically lasts only a few minutes at any one location on Earth, Proba-3 can create an artificial eclipse that lasts up to six hours in each orbit. This allows scientists to study subtle changes in the solar corona for much longer periods than during a short, natural solar eclipse.
In February 2026, engineers temporarily lost contact with Proba-3 after a software glitch. After weeks of recovery efforts, the spacecraft was successfully revived, its software was patched and formation flight resumed.
A diagram explaining the Proba-3 space mission, which will include two satellites flying in formation with unprecedented precision, to observe the solar corona (Illustration by Valentin Rakovsky and Stefan Kogok/AFP via Getty Images)
AFP via Getty Images
Solar wind and sun corona
The solar wind is constantly flowing away from the Sun, carrying charged particles throughout the solar system and causing geomagnetic storms capable of disrupting satellites, radio communications, navigation systems and even power grids on Earth. Understanding how the solar wind forms and accelerates is one of the biggest unanswered questions in solar physics. Proba-3’s main science target is the source of the solar wind – the solar corona, the Sun’s extremely hot outer atmosphere, which reaches temperatures of more than a million degrees Celsius. This is despite the fact that the Sun’s visible surface – its photosphere – is much cooler. NASA has spacecraft (SOHO’s LASCO, Solar Orbiter’s Metis and… It goes CCOR-1) studies the corona using occulting disks, but Proba-3 can appear much closer to the sun, about 44,000 miles (70,000 km) above the sun’s surface, an area that has remained largely hidden from previous space telescopes. This inner aura is already giving up its secrets to Proba-3.
This time-lapse animation captures a coronal mass ejection (CME) at top right, and combines observations made on July 16, 2025, over an hour and a half by three different European instruments aboard different missions: the Sun’s disk and low corona (artificially colored yellow), as captured by the Solar Extreme Ultraviolet (SWAP) telescope aboard Proba-2; The outer corona (red) observed by the LASCO C2 instrument on SOHO; The inner corona (green), imaged in detail by Proba-3’s ASPIICS Coronagraph, fills the gap.
ESA/NASA/Probe-2/Probe-3/SOHO/SWAP/ASPEX/LASCO C2
The solar wind is faster than expected
The mission’s first scientific results have already surprised researchers since its launch The first artificial solar eclipse in orbit. By tracking small blobs of plasma moving through the inner corona, scientists found that parts of the so-called slow solar wind are traveling at speeds of 250 to 500 kilometers per second, three to four times faster than previous models predicted close to the Sun. “In the inner corona, a region that is very difficult to observe, we saw slow solar winds moving three to four times faster than expected.” He said Andre Zhukov of the Royal Observatory of Belgium, principal investigator of Proba-3’s ASPIICS instrument and lead author of the study published In March. The researchers also observed the complex flows, jets and streams moving through the corona in exquisite detail.
Total solar eclipses have led to major scientific breakthroughs for more than a century, most famously providing one of the first observational tests of Einstein’s theory of general relativity in 1919.
Further reading
