Yesterday morning, at 8 a.m. EDT, the Sun unleashed the largest flare we've seen in the last 12 years. A flare, which is a localized explosion of light and particles on the Sun, can also trigger a secondary blast of particles into interplanetary space. These particles can zoom toward Earth at a few million miles an hour, hit our atmosphere, and create aurorae, or glittering curtains of light commonly known as the Northern Lights. Tonight, we may see aurora as far south as Kentucky.

The Sun's level of activity goes up and down in an 11-year cycle: sometimes it produces a ton of large flares, and sometimes it's pretty quiet. Every solar cycle, the Sun delivers a few standout punches. This current solar cycle, however, is the quietest in the last 100 years. It's pretty notable that such a large flare came out of such a calm period. These flares are the hardest to predict, but the most interesting to study—and we'll learn a lot more in the days to come.