A long filament snaked across half the Sun this week (Jan. 19-23, 2014). This one, if it were straightened out, would be about 500,000 miles long. Filaments are elongated clouds of cooler gases, tethered above the solar surface by powerful magnetic forces. They are often unstable and prone to erupting, although so far this one has remained intact. The images, taken in extreme ultraviolet light, actually show ionized Helium at about 60,000 degrees C. Credit: Solar Dynamics Observatory/NASA.
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