The Sun's outer atmosphere is significantly hotter than the surface, a mysterious situation that has puzzled astronomers for decades.
Nanoflares - minor eruptions from the Sun, too small to be detected from Earth, have been postulated as the cause of this unusual heating.
A new sounding rocket, managed by NASA, has provided the best evidence yet for these flares. This flight collected data for just six minutes, possibly answering a mystery that has perplexed the greatest astronomers in the world for many years.
"The EUNIS mission, short for Extreme Ultraviolet Normal Incidence Spectrograph, launched on April 23, 2013, gathering a new snapshot of data every 1.3 seconds to track the properties of material over a wide range of temperatures in the complex solar atmosphere," NASA officials wrote in a video description, showing the results.
The surface of the sun is roughly 10,000 degrees Fahrenheit, while the corona, the atmosphere of the Sun, can reach temperatures of one million degrees Fahrenheit.
"That's a bit of a puzzle. Things usually get cooler farther away from a hot source. When you're roasting a marshmallow you move it closer to the fire to cook it, not farther away," Jeff Brosius from the Goddard Space Flight Center, said.
Sounding rockets are among the least expensive of all NASA missions. They can typically lift payloads into the upper atmosphere, and are often used in conjunction with high-altitude balloons.
A spectrograph machine, tuned to study solar emissions from the surface of the Sun to the corona, was used on board the EUNIS mission to record stellar activity. The device had to be lifted to the upper atmosphere in order to achieve the readings it recorded. High-energy ultraviolet wavelengths of electromagnetic radiation are largely absorbed by the atmosphere surrounding Earth. The EUNIS rocket peaked at an altitude of around 200 miles, with a total mission duration of around 15 minutes. Instruments aboard the craft were jettisoned, and returned to Earth via parachutes for re-use in later missions.
A video showing evidence for coronal heating by nanoflares was produced and released by the Goddard Space Flight Center.
Strangely, a person caught in the coronal of the Sun would not burn to death. Provided air and pressure were accounted for, the unfortunate space traveler would freeze to death in the million-degree gas. This is because the atmosphere of the Sun is so thin, very little heat energy would be delivered to the body.
Investigation of nanoflares as the possible source of coronal heating was published in The Astrophysical Journal.
