Northern lights dazzle over Chicagoland and across Illinois: PHOTOS

CHICAGO - It will go down as one of the most widely photographed northern lights episodes on record.

What we know:

More than 30 states were able to view them Tuesday night, including across Illinois and in Chicagoland. They were triggered by explosions of energized plasma from the sun — specifically a sunspot group designated 4274. This part of the sun has been sending flares into space for days, and an X-class flare (the strongest type) merged with an earlier flare to create the aurora borealis here.

These flares create Coronal Mass Ejections (CMEs), which, if aimed just right, can hit the earth’s magnetic field and charge various gases high in our atmosphere, causing them to glow and pulse. The usual green color of the northern lights is due to "excitement" of oxygen molecules around 60-180 miles up.

Reds are typically seen only in strong events (like this one) and are due to oxygen reacting at higher altitudes — usually 180-250 miles high. Pinks and purples involve nitrogen and are lower in altitude, which is why these colors are often found lower in the display from the viewer’s vantage point.

Dig deeper:

Last night’s eruption involved a G5 geomagnetic storm — the strongest classification. This was also a rare Ground Level Event or GLE. The solar flare was so powerful that protons penetrated the atmosphere and reached the earth’s surface. This happens roughly once every 20 years.

What's next:

It's too early to predict whether an encore will occur Wednesday night.