100. Sun Burn
The sun is at the peak of its 11-year cycle. What will that bring to the skies in 2013?
On August 31 the sun expelled a cloud of 100,000-degree Fahrenheit plasma at more than 900 miles per second. NASA's newest sun-viewing satellite, the Solar Dynamics Observatory, tracked the vast filament, which measured about 30 Earths across when this image was taken. Get ready for many more such spectacular images: This year marks the peak of the sun's 11-year cycle of activity, which means an increased risk of damage to satellites—but also a high chance of brilliant aurora displays.