1st-ever radio images of an annular solar eclipse showcase the sun's extended corona

This composite shows radio images of the recent annular eclipse on top, with illustrations of their visible-light counterparts below.
This composite shows radio images of the recent annular eclipse on top, with illustrations of their visible-light counterparts below. (Image credit: Sijie Yu)

Your social media feeds might've been filled over the past couple of weeks with photos of the recent "ring of fire" annular eclipse, which crossed the western U.S. on Oct. 14. But it wasn't just photographers who imaged the celestial event.

Scientists from the New Jersey Institute of Technology’s Center for Solar-Terrestrial Research (NJIT-CSTR) used the new Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA) in California to capture the first-ever radio images of an annular solar eclipse.

Using a set of 352 antennas measuring radio wavelengths between approximately 20 and 88 megahertz (MHz), the team captured images of the eclipse's ring, which lasted for nearly an hour in the radio spectrum. By contrast, the visible light experience solar enthusiasts admired lasted only a few minutes. That's because the radio sun is about twice as large as the visible solar disk. 

Related: Annular solar eclipse of 2023 wows skywatchers with spectacular 'ring of fire' (photos, video)

"From our observatory site in California we were not in the belt to see the annular eclipse, yet we’ve been able to 'see' it all clearly unfold in radio, which reveals a much larger solar disk than its visible counterpart thanks to its sensitivity to the extended solar corona," Bin Chen, NJIT-CSTR associate professor of physics, said in a statement

The corona is not usually visible from the ground, except during a total solar eclipse (like the one occurring on Apr. 8, 2024), but OVRO-LWA has changed the game. Now, with this instrument, the corona is visible to us at all times — and researchers are particularly eager to observe it during other eclipses.

"Science-wise, this is a unique opportunity to study the sun's extended corona with the highest resolution possible at these wavelengths, taking advantage of the moon's limb as a moving 'knife edge' to increase the effective angular resolution," said Chen.

The team is now developing a process to produce "near-real-time solar images" for the public. 

"These eclipse images serve as a proof-of-concept for this effort," said Chen. "The unprecedented data products coming soon will open new opportunities for discovery in solar astronomy and space weather studies."

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Stefanie Waldek
Contributing writer

Space.com contributing writer Stefanie Waldek is a self-taught space nerd and aviation geek who is passionate about all things spaceflight and astronomy. With a background in travel and design journalism, as well as a Bachelor of Arts degree from New York University, she specializes in the budding space tourism industry and Earth-based astrotourism. In her free time, you can find her watching rocket launches or looking up at the stars, wondering what is out there. Learn more about her work at www.stefaniewaldek.com.