For the first time, scientists have captured solar "raindrops"—cooling plasma streams cascading back toward the sun—in breathtaking detail using a ground-based telescope in California. These vivid images, which also showcase vast plasma arches and intricate stream structures, offer an unprecedented glimpse into the dynamic behavior of the sun’s outer atmosphere, the corona.
The phenomenon known as coronal rain occurs when superheated plasma in the sun’s corona cools, condenses, and follows magnetic field lines back down to the solar surface. These streams, along with solar prominences—large, looping arcs of plasma—are among the finely detailed structures observed in the new images.
The visuals, captured in hydrogen-alpha light and artificially colorized in shades of pink, were taken using time-lapse technology that eliminates distortion caused by Earth's turbulent atmosphere. The breakthrough was made possible by researchers from the U.S. National Science Foundation's National Solar Observatory and the New Jersey Institute of Technology (NJIT), and their findings were published this week in Nature.
“These are by far the most detailed observations of this kind, revealing features we’ve never seen before—and we’re not entirely sure what some of them are,” said study co-author Vasyl Yurchyshyn, a research professor at NJIT.
The images were captured using the 1.6-meter Goode Solar Telescope at California’s Big Bear Solar Observatory (BBSO), now outfitted with a cutting-edge adaptive optics system called Cona. This technology uses a laser to correct for distortions in Earth’s upper atmosphere in real time.
“Cona is like a supercharged autofocus for the sky,” said Nicolas Gorceix, chief observer at BBSO. The system reshapes a specialized mirror 2,200 times per second, dramatically sharpening resolution. Previously, ground-based solar observations were limited to features around 1,000 kilometers (620 miles) across. With Cona, scientists can now resolve structures as small as 63 kilometers (39 miles).
The sun’s corona—Latin for "crown"—remains one of the most mysterious regions in the solar system. Normally hidden by the bright light of the sun’s surface, or photosphere, it’s visible only during total solar eclipses. The corona is puzzling not just for its beauty but for its extreme temperatures: although it is more diffuse, it’s millions of degrees hotter than the sun’s surface.
This region is of special interest to solar physicists because it’s the origin point of the solar wind—a constant stream of charged particles that flows outward through the solar system. When this stream interacts with Earth's magnetic field, it can trigger geomagnetic storms and dazzling auroras.
Following the success of Cona at BBSO, plans are already underway to implement the technology at the Daniel K. Inouye Solar Telescope in Maui, Hawaii. At 4 meters across, it's the largest solar telescope in the world and could offer even more detailed views of our star’s complex outer layers.