Sharpest Solar Images Ever: Pink 'Raindrops' On The Sun Captured In Unprecedented Detail

Advanced ground-based telescopes use adaptive optics (AO) to produce sharp images by correcting atmospheric distortion, capturing stunning views of planets, stars, and celestial objects. Recently, a team at the National Solar Observatory applied AO technology to study the Sun's corona in remarkable detail, as per Science Alert. The corona, the Sun's outermost layer, stretches millions of kilometres into space and is mysteriously hotter than the underlying photosphere, a phenomenon known as the 'coronal heating problem.' This region is governed by powerful magnetic fields and is the source of coronal mass ejections (CMEs), which can interact with Earth's magnetosphere, triggering auroras and geomagnetic storms.

Observing the Sun's corona is challenging due to its dimness compared to the Sun's surface. Typically, it's visible during total solar eclipses or through space-based coronagraphs that mimic an eclipse. However, researchers have now used Adaptive Optics (AO) to study the corona from Earth. AO employs computer-controlled, deformable mirrors to counteract atmospheric interference, producing clear images.

A team from the National Solar Observatory and the New Jersey Institute of Technology developed an AO system for the 1.6-meter Goode Solar Telescope, enabling precise observations of the corona's fine structure.

"Resolving fine structures in the Sun's corona may provide key insights into rapid eruptions and the heating of the corona," the authors write in their research article. Here we present observations with coronal adaptive optics reaching the diffraction limit of a 1.6-m telescope to reveal very fine coronal details," the authors wrote in a paper titled Observations of fine coronal structures with high-order solar adaptive optics.

Solar prominences, loops, and rain are all composed of plasma, and understanding these phenomena requires observing their fine details. Key questions remain unanswered, such as how plasma in the corona is heated to millions of kelvins when the Sun's surface is only 6,000 K, and what triggers eruptions. 

"The turbulence in the air severely degrades images of objects in space, like our Sun, seen through our telescopes. But we can correct for that. It is super exciting to build an instrument that shows us the Sun like never before," Dirk Schmidt, NSO Adaptive Optics Scientist, who led the development, said in a press release.

This video captures a dynamic prominence featuring a large-scale twist and cascading coronal rain.
Coronal rain occurs when strands of coronal plasma cool and descend back to the Sun's surface.

"Raindrops in the Sun's corona can be narrower than 20 kilometres. These findings offer new, invaluable observational insight that is vital to test computer models of coronal processes," said NSO Astronomer Thomas Schad. "

Another video displays a dense, cool quiescent prominence with intricate internal flows.

The next video showcases post-flare coronal rain, where plasma strands, guided by the Sun's magnetic field lines, cascade along curved paths rather than straight lines. These images, captured at the highest resolution ever achieved, reveal unprecedented details of this phenomenon.

Solar telescopes using adaptive optics (AO) have historically detailed the Sun's surface with 1,000 km precision but struggled to image the corona. The new coronal AO system, developed with contributions from NSO Chief Technologist Thomas Rimmele, achieves 63 km resolution, the theoretical limit of the 1.6-meter Goode Solar Telescope. Described as transformative by NJIT's Philip Goode, this technology enhances resolution tenfold, revolutionising solar science. 

"With coronal adaptive optics now in operation, this marks the beginning of a new era in solar physics, promising many more discoveries in the years and decades to come," said Mr Goode.