Decoded: Forget the eclipse, stare into the corona
The total solar eclipse enveloping America — we’ll barely notice a dimming up here — is a pretty cool, rare event. But that’s not all it is. Take a tour of what the geekiest of the space geeks will be watching for, as the eclipse reveals brand new facts about space.
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TRAVELLING THE PATH OF TOTALITY
The shadow cast by the moon will traverse the U.S. at speeds up to 3,878 km/hour, so those in its path will experience totality (total darkness) only for a couple of moments. To prolong the moment, NASA has retrofitted two old bomber jets with telescopes to chase the eclipse across the continent for a full seven minutes.
Among other things, they will observe the sun’s mysterious outer layer, or chromosphere, and its upper atmosphere, the corona. On a normal day, the immense brightness of the photosphere, the yellow surface of the sun, washes out our view, even with the best telescopes.
WHY IS THE SUN SO HOT?
The sun’s outer atmosphere blazes at up to one million Celsius. But the surface is closer to 6,000 C. Why? It has to do with the complex magnetic arcs, storms and waves in the star's plasma. Nanoflares, tiny bursts of brightness in the corona, are believed to have an out-sized impact: A single one has the energy of 240 megatons of TNT. They’ve never been observed or photographed directly. Today, NASA is going to take a stab at it.
WHAT’S MERCURY MADE OF?
Because it’s so close to the sun and sets at almost the same time, Mercury is incredibly hard to observe in detail from Earth — usually. Just before and after totality, when the sky is quite dark, infrared telescopes will make a heat map of the mysterious planet’s surface, revealing a more precise picture of its makeup.
LEARNING TO X-RAY THE SUN
The sun constantly emits X-rays. X-ray imagers are used to observe things like the solar wind that creates the Northern Lights and other phenomenon that can affect Earth's satellites. During the eclipse, scientists will be making these instruments more accurate by pointing them at the black spot where the sun was and teaching them to recognize it as total X-ray darkness.