The sharpest images yet taken of the sun’s atmosphere reveal
superfine threads of hot plasma draped across small regions that have appeared
rather bland until now.
Finding these slender strands is essential for understanding
how energy moves around in the sun’s atmosphere, says Amy Winebarger, a solar
physicist at NASA’s Marshall Space Flight Center in Huntsville, Ala. Such intel
could help astronomers understand why the corona — the outer part of the sun’s
atmosphere — is hundreds
of times hotter than the sun’s surface (SN: 8/20/17).
Some of the newfound filaments measure just
over 200 kilometers wide — they would barely fit between Washington,
D.C., and Philadelphia. No one has seen them before because previous images could
not resolve such fine detail in the solar corona.
The pictures come courtesy of NASA’s High-Resolution Coronal
Imager, or Hi-C. This small ultraviolet telescope occasionally gets
hurled into space atop a rocket and then has about five minutes to snap
pictures of the sun before falling back to Earth.
“We’re seeing threads pop out where we see nothing in other
instruments,” says Winebarger, a coauthor of the new study, published in the April
1 Astrophysical Journal.
Hi-C spotted the solar gossamer during its second successful flight in May 2018, during which it zeroed in on a region of the sun bursting with magnetic activity. The areas laced with plasma threads in the Hi-C images appear as just a muddle of light in concurrent images from NASA’s orbiting Solar Dynamics Observatory, hinting that ever smaller structures on the sun are still waiting to be discovered.