For the first time, scientists have recorded "raindrops" on the Sun – cool streams of plasma falling back towards the solar surface – in unprecedented detail using a ground-based telescope in California.
These vividly coloured images, which reveal both large plasma arches and delicate stream-like structures, offer the most detailed glimpse yet into the dynamic behaviour of the Sun’s outer atmosphere, known as the corona.
This phenomenon, known as coronal rain, occurs when superheated plasma in the corona cools, condenses, and falls back along magnetic field lines towards the Sun’s surface. These streams, along with solar prominences — large, looping arcs of plasma — are among the intricate structures captured in the new observations.
The visuals were recorded in hydrogen-alpha light and colourised in artificial pink hues. They were taken using time-lapse imaging technology, which compensates for distortions caused by Earth's turbulent atmosphere. This achievement is the result of work by researchers from the U.S. National Science Foundation's National Solar Observatory and the New Jersey Institute of Technology (NJIT). Their findings were published this week in Nature.
“These are the most detailed observations to date, showing features we’ve never seen before — and some that we still don’t fully understand,” said Vasyl Yurchyshyn, a research professor at NJIT and co-author of the study.
The images were captured by the 1.6-metre Goode Solar Telescope at the Big Bear Solar Observatory (BBSO) in California, where an advanced adaptive optics system named Cona has now been installed. This system uses a laser to correct for distortions in Earth’s upper atmosphere in real time.
“Cona is like a supercharged autofocus for the sky,” explained Nicolas Gorceix, chief observer at BBSO. The system reshapes a specialised mirror 2,200 times per second, dramatically improving image resolution. Previously, solar features smaller than 1,000 kilometres (620 miles) were difficult to detect from the ground — but with Cona, scientists can now observe structures as small as 63 kilometres (39 miles).
The Sun’s corona — Latin for "crown" — is one of the most mysterious parts of the solar system. Normally hidden by the brightness of the Sun’s surface (the photosphere), the corona is visible only during total solar eclipses. Despite being less dense, it is several hundred thousand degrees hotter than the Sun’s surface — a longstanding puzzle in solar physics.
This region is of particular interest to solar physicists because it is the origin of the solar wind, a continuous stream of charged particles. When this stream interacts with Earth’s magnetic field, it can trigger geomagnetic storms and produce dazzling auroras.
Following successful testing at BBSO, the Cona system is now being installed at the Daniel K. Inouye Solar Telescope in Maui, Hawaii. With a 4-metre-wide aperture, it is the largest solar telescope in the world and promises even deeper insights into the complex outer layers of the Sun.
