Raindrops in the Suns Corona

A revolutionary advancement in solar observation has been achieved by scientists from the U.S. National Science Foundation’s National Solar Observatory (NSO) and the New Jersey Institute of Technology (NJIT). Using an innovative new optical system known as coronal adaptive optics, the research team has captured the clearest images to date of the Sun’s enigmatic outer atmosphere, the corona.

Published in Nature Astronomy, the findings mark a transformative step in understanding solar activity and space weather, with implications for future scientific exploration of coronal heating and solar eruptions.

Raindrops in the Suns Corona: Breakthrough adaptive optics reveal unprecedented detail in solar atmosphere

The Sun’s corona is a region of extreme temperatures and violent dynamics, visible to the naked eye only during total solar eclipses. Ground-based observation of this layer has long been hindered by the Earth's atmospheric turbulence, which introduces blur and degrades image quality. Now, a team led by NSO’s Dirk Schmidt has developed a pioneering solution: a high-speed adaptive optics system capable of compensating for atmospheric distortions in real-time.

Installed on the 1.6-meter Goode Solar Telescope (GST) at Big Bear Solar Observatory in California, operated by NJIT’s Center for Solar-Terrestrial Research (CSTR), the system, dubbed Cona, enables high-resolution imaging of coronal features previously obscured.

“Atmospheric turbulence severely degrades images of solar structures,” said Schmidt. “With coronal adaptive optics, we can correct that and finally see the corona in exquisite detail.”

Dynamic solar phenomena captured in unprecedented clarity

Among the most striking results are time-lapse sequences capturing dynamic solar events with unparalleled precision. One such sequence reveals the intricate restructuring of a solar prominence, an arched plasma structure, exposing fine, turbulent internal flows. Another shows a narrow, rapidly forming and collapsing plasma stream, revealing features never before seen.

"These are by far the most detailed observations of this kind. It’s not quite clear what we’re seeing, which makes it all the more exciting," said Vasyl Yurchyshyn, NJIT-CSTR research professor and co-author.

The team also documented coronal rain, plasma that cools and condenses before falling back to the solar surface. According to NSO astronomer Thomas Schad, the new imagery shows that some of these plasma strands are narrower than 20 kilometers, offering essential observational data to refine models of coronal physics.

A separate sequence revealed how solar plasma twists and dances along magnetic field lines within a prominence, providing a dramatic view of the Sun’s dynamic magnetic environment.

All images were captured in hydrogen-alpha light using the Cona system and artificially colorized to reflect the relative intensity of this spectral emission.

Solving a decades-old limitation in solar imaging

The solar corona is heated to millions of degrees, far hotter than the Sun’s visible surface, but the mechanism behind this has remained elusive. The new adaptive optics system provides critical insight into cooler plasma structures, which could hold clues to solving the coronal heating problem and improving predictions of solar storms.

Cona operates by reshaping a deformable mirror 2,200 times per second, counteracting distortions introduced by the atmosphere. "Think of it as a supercharged version of the autofocus in your smartphone, but instead of compensating for hand shake, it corrects for the turbulence in the air," explained Nicolas Gorceix, BBSO’s Optical Engineer and Chief Observer.

Traditional adaptive optics have long enhanced observations of the Sun’s surface, but until now, the resolution for off-limb coronal features had stagnated, unchanged for over 80 years. The new system achieves a spatial resolution of 63 kilometers, matching the theoretical limit of the Goode Solar Telescope.

"This closes a long-standing gap in our observational capabilities. Now we can study coronal features with a level of detail once thought impossible from the ground," said Thomas Rimmele, NSO Chief Technologist and a pioneer in solar adaptive optics.

Looking ahead: A new era for solar physics

With coronal adaptive optics now operational at GST, the door is open to a new era of solar research. The team is actively working to implement the technology at the 4-meter NSF Daniel K. Inouye Solar Telescope in Maui, Hawai?i, the world’s largest solar telescope, where even finer details could be observed.

"This is a game-changer. Boosting resolution by a factor of ten will reveal structures we’ve never imagined," said Schmidt.

The research team anticipates that this technology will be adopted globally, transforming ground-based solar astronomy. "This marks the beginning of a new era. With coronal adaptive optics, the possibilities for discovery are truly vast," said Philip R. Goode, co-author and distinguished research professor of physics at NJIT-CSTR.

The full study, "Observations of fine coronal structures with high-order solar adaptive optics," is available in Nature Astronomy. Authors include Dirk Schmidt (NSO), Thomas A. Schad (NSO), Vasyl Yurchyshyn (NJIT), Nicolas Gorceix (NJIT), Thomas R. Rimmele (NSO), and Philip R. Goode (NJIT).

Cona Coronal Adaptive Optics System