Best-ever images of solar corona captured

US astronomers have released what they say are the highest-resolution images ever captured of the sun's corona, its million-degree outer atmosphere. NASA's High Resolution Coronal Imager, or Hi-C, launched July 11 on a sounding rocket, captured the 16-megapixel images in an extreme ultraviolet wavelength. "Even though this mission was only a few minutes long, it marks a big breakthrough in coronal studies," Leon Golub of the Harvard-Smithsonian Center for Astrophysics said. The new images contain five times as much detail as the next-best observations by NASA's Solar Dynamics Observatory, a release from the Harvard-Smithsonian center reported. The sun's corona is filled with ionized gas, or plasma, so hot the light it emits is mainly at X-ray and extreme-ultraviolet wavelengths. Solar scientists have long tried to understand why the corona is so hot, and why it erupts in violent solar flares and related blasts known as "coronal mass ejections," which can produce harmful effects when they hit Earth. Hi-C focused on an active region on the sun featuring a sunspot selected specifically for its large size and active nature. "Because of the intense solar activity we're seeing right now, we were able to clearly focus on a sizeable, active sunspot and achieve our imaging goals," Jonathan Cirtain, a senior NASA heliophysicist said. "We have an exceptional instrument and launched at the right time."