On Monday, while the rest of us were celebrating Labor Day, the sun let out a little stellar burp, which scientists politely call a coronal mass ejection. That in and of itself isn't that unusual: The sun is a giant ball of super-hot charged particles called plasma being roiled around by a powerful magnetic field. Sometimes, things just get messy.
When the sun spits out plasma, it has to go somewhere, and often it reaches Earth's atmosphere. That's not always a good thing, since plasma and other particles from the sun—collectively called space weather—can interfere with our GPS and communications satellites.
But there's one truly beautiful consequence: auroras, streams of greenish light dancing across the night near the poles (in the Northern Hemisphere, the phenomenon is known as aurora borealis or the Northern Lights; in the south, aurora australis). The spectacle is caused by electrons hitting the top layers of Earth's atmosphere, hitting air molecules, and giving those molecules their energy in a burst of light.
Auroras can most commonly be spotted between 60 and 75 degrees north or south of the equator—that's places like Alaska, the southern half of Greenland, Scandinavia, the northern half of Russia, and the outer fringes of Antarctica. In fact, those areas can catch an aurora about once every two nights.
The mainland U.S. is not so spoiled—but thanks to Monday's coronal mass ejection, a swath of the northern midwest and northeast may be treated to an incredible light show Wednesday night and Thursday morning. That includes parts of Washington, Montana, the Dakotas, Minnesota, Wisconsin, Michigan, New York and New England—around the yellow line in this map:
If you're in that area, here's what to do. The aurora goes on during night and day alike, but you can only actually see the light show against a dark sky. That means go outside at night, but also try to get away from cities and other brighter places. Tuesday night was the full moon, which might also make the aurora look a little fainter. You'll also need to avoid clouds that can block your view.
Precisely where and when the aurora will show up is beyond prediction, so be prepared to spend some time enjoying the great outdoors. It also comes and goes in spurts of about a half hour.
You can check NOAA's updated aurora forecast closer to sunset to see if your odds have improved or declined. It will show you the progression of night and day, the predicted range of the aurora, and how likely it is to occur. (September 7 at 0300 UT is September 6 at 10 p.m. Eastern Time.)
If you miss out on the show Wednesday night, you can always check in with the Canadian Space Agency's nightly livestream of Yellowknife's colorful skies.