New Imaging Technique Captures Sun's Corona In Dreamy Detail

When imaging objects in space, distance isn’t the only challenge: Earth’s atmosphere gets in the way, too. As turbulence ripples through our planet’s protective layer, images of stars, the Moon, and even other galaxies become fuzzy and distorted. Correcting these flaws requires adaptive optics, or AO, a technique that uses multiple imaging technologies to compensate for disturbances in the atmosphere. 
But conventional AO falls short of capturing the Sun. The technique relies on a point source to (literally) shine a light on how much atmospheric distortion is occurring at a given time, but the Sun is too close and too bright to allow another star to perform that role. This means that while AO has helped astronomers image exoplanets and stunning nebulae, our own Sun has been off-limits—until now.
Researchers at the National Solar Observatory (NSO) and Big Bear Solar Observatory have developed a version of AO that works with our bright central star. Dubbed coronal adaptive optics, or CAO, the technique relies on a mirror that “constantly reshapes itself 2,200 times per second to counteract the image degradation caused by turbulent air,” according to the Association of Universities for Research in Astronomy (AURA). These movements “flatten” the parts of an image that would otherwise bubble, producing a clearer image.
CAO can capture the Sun’s corona, or outer plasma layer, at a reported resolution of 63 kilometers—and to prove it, the team has shared some of their first images. In the above image, a prominence rises from the Sun’s “fuzzy” surface, which is covered in short-lived plasma jets called spicules. The picture below is a still shot from a 4-minute time-lapse of the corona’s constant restructuring. The faint streaks on the right are coronal rain—cool, dense plasma that has condensed into blobs—falling onto the Sun’s surface. 
The new technique (and a series of additional images) is described in a paper published May 27 in Nature Astronomy.
“Raindrops in the Sun’s corona can be narrower than 20 kilometers,” said NSO astronomer and study co-author Thomas Schad. “These findings offer new invaluable observational insight that is vital to test computer models of coronal processes.”
The researchers have made their time-lapse videos available on YouTube through a trio of unlisted links:
Post-flare coronal rain
Dynamic prominence with large-scale twist alongside raining coronal material
Dense and cool quiescent prominence with complex internal flows
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