The Sun’s Hidden Threads Revealed in Gorgeous Solar Flare Photos

Astronomers utilizing the Inouye Solar Telescope have captured the sharpest solar flare images ever taken, revealing delicate, threadlike plasma loops as narrow as 21 kilometers.

These ultra-fine structures, caught during an explosive X-class flare, provide the clearest evidence yet of the Sun’s hidden architecture and may represent the fundamental building blocks of flare activity.

Record-Breaking Solar Flare Imaging

The most detailed images ever taken of a solar flare at the H-alpha wavelength (656.28 nm) are giving scientists a new look at the Sun’s magnetic structures and may improve our ability to predict space weather. Using the U.S. National Science Foundation (NSF) Daniel K. Inouye Solar Telescope, operated by the NSF’s National Solar Observatory (NSO), researchers recorded remarkably fine strands of dark coronal loops during the fading stage of an X1.3-class flare on August 8, 2024, at 20:12 UT. These loops measured an average width of 48.2 km, with some appearing as slim as 21 km. They are the narrowest coronal loops ever seen, representing a major advance in pinpointing the fundamental scale of these features and expanding the boundaries of solar flare modeling.

Coronal loops are glowing arcs of plasma shaped by the Sun’s magnetic field lines. They often appear before solar flares, which occur when certain magnetic field lines twist and break, releasing bursts of energy. These eruptions drive solar storms that can disrupt Earth’s satellites, power grids, and communication systems. By observing at the H-alpha wavelength (656.28 nm), the Inouye telescope can highlight specific features of the Sun that remain invisible in other kinds of observations.

A high-cadence, high-resolution film of the flare, captured by the Inouye Solar Telescope, has been sped up 100 occasions. Both vibrant ribbons and darkish overlying coronal loops are seen. The picture is about 4 Earth diameters on all sides. Credit: NSF/NSO/AURA

First X-Class Flare Observed by Inouye

“This is the first time the Inouye Solar Telescope has ever observed an X-class flare,”explains Cole Tamburri, the examine’s lead writer. Tamburri is supported by the Inouye Solar Telescope Ambassador Program whereas pursuing his Ph.D. on the University of Colorado Boulder (CU). Funded by the NSF, this system is designed to coach Ph.D. college students as a part of a related community of early-career scientists at U.S. universities who will share experience in Inouye information evaluation throughout the photo voltaic analysis neighborhood. “These flares are among the most energetic events our star produces, and we were fortunate to catch this one under perfect observing conditions.”

The analysis group, which included scientists from the NSO, the Laboratory for Atmospheric and Space Physics (LASP), the Cooperative Institute for Research in Environmental Sciences (CIRES), and CU, targeting the fragile magnetic loops unfold above the flare’s vibrant ribbons. In complete, lots of of those options had been seen, averaging round 48 km in width, with some loops proper on the telescope’s decision restrict. “Before Inouye, we could only imagine what this scale looked like,” Tamburri explains. “Now we can see it directly. These are the smallest coronal loops ever imaged on the Sun.”

Pushing Resolution Limits in Solar Science

The Inouye’s Visible Broadband Imager (VBI) instrument, tuned to the H-alpha filter, can resolve options all the way down to ~24 km. That is over two and a half occasions sharper than the next-best photo voltaic telescope, and it’s that leap in decision that made this discovery doable. “Knowing a telescope can theoretically do something is one thing,” Maria Kazachenko, a co-author within the examine and NSO scientist, notes. “Actually watching it perform at that limit is exhilarating.”

While the unique analysis plan concerned learning chromospheric spectral line dynamics with the Inouye’s Visible Spectropolarimeter (ViSP) instrument, the VBI information revealed one thing sudden treasures—ultra-fine coronal constructions that may straight inform flare fashions constructed with advanced radiative-hydrodynamic codes. “We went in looking for one thing and stumbled across something even more intriguing,” Kazachenko admits.

Confirming Theories on Coronal Loop Scales

Theories have lengthy urged coronal loops might be anyplace from 10 to 100 km in width, however confirming this vary observationally has been unimaginable—till now. “We’re finally peering into the spatial scales we’ve been speculating about for years,” says Tamburri. “This opens the door to studying not just their size, but their shapes, their evolution, and even the scales where magnetic reconnection—the engine behind flares—occurs.”

Perhaps most tantalizing is the concept these loops is perhaps elementary constructions—the basic constructing blocks of flare structure. “If that’s the case, we’re not just resolving bundles of loops; we’re resolving individual loops for the first time,” Tamburri provides. “It’s like going from seeing a forest to suddenly seeing every single tree.”

Breathtaking Imagery and Landmark Moment

The imagery itself is breathtaking: darkish, threadlike loops arching in a glowing arcade, vibrant flare ribbons etched in virtually impossibly sharp reduction—a compact triangular one close to the middle, and a sweeping arc-shaped one throughout the highest. Even an off-the-cuff viewer, Tamburri suggests, would instantly acknowledge the complexity. “It’s a landmark moment in solar science,” he concludes. “We’re finally seeing the Sun at the scales it works on.” Something made solely doable by the NSF Daniel Ok. Inouye Solar Telescope’s unprecedented capabilities.

Reference: “Unveiling Unprecedented Fine Structure in Coronal Flare Loops with the DKIST” by Cole A. Tamburri, Maria D. Kazachenko, Gianna Cauzzi, Adam F. Kowalski, Ryan French, Rahul Yadav, Caroline L. Evans, Yuta Notsu, Marcel F. Corchado-Albelo, Kevin P. Reardon and Alexandra Tritschler, 25 August 2025, The Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/adf95e

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