As you may have seen for yourself, on the evening of October 10, 2024, the sky lit up with aurorae borealis (and australis), also known as the northern (southern) lights. They were seen really far south, including down to 38°N, which I know for a fact because finally, after my entire life of waiting, I FINALLY SAW THE FREAKING AURORA!!!!

According to SpaceWeather.com it was seen as far south as Puerto Rico! The cause was a massive coronal mass ejection (or CME) from the Sun, triggered by a sunspot called Active Region 3848. This was a huge sunspot; I saw it naked eye just using my eclipse glasses on October 8. The sunspot blew out a big flare, class X1.8, which triggered the coronal mass ejection. While the flare wasn’t as powerful as previous ones form this spot, it lasted a long time, several hours, which is probably what kicked off the CME.

Flares are immense explosions of energy that occur when magnetic field lines in sunspots get tangled up, snap, reconnect, and release their stored-up energy as a huge flash of energy and subatomic particles. They can easily be the equivalent of billions — yes, billions — of one-megaton nuclear bombs. They are intense and usually short. CMEs, on the other hand, are much larger-scale explosions when a billion tons of matter (usually hydrogen and other particles) are lifted off and launched away from the Sun a high speed. They don’t emit much light, but are very powerful (I like to say flares and CMEs are like tornadoes and hurricanes; intense and local versus huge and ferocious). The CME carries its own magnetic field with it, and if it a) hits Earth and 2) efficiently couples with our magnetic field, a lot of particles slam down into the atmosphere funneled by Earth’s magnetic field lines. They ionize the atoms and molecules there, and when the electrons recombine with their parent atoms and molecules, they release light at very specific wavelengths, or colors. Red, green, yellow, even pink and purple depending on how the colors mix.

That’s the aurora. I explain this in more detail in Crash Course Astronomy: The Sun:

The CME from October 8 was aimed right at us, and was very good at driving vast waves of charged subatomic particles into our air, causing it to glow. Most times the aurorae are limited to high latitudes (near the poles), but a powerful one like this can drive them farther toward mid-latitudes.

I got alerts and saw what was going on in Europe — my nephew in Scotland told me the aurora was bright and directly overhead, which was a good sign. If they’re near the zenith at 50° N latitude, then there’s a good chance I could see them in Virginia. I was alerting people on Bluesky when a reader told me they were seeing them in Reston, about 200 km northwest of me.

I ran outside, and sure enough, even by eye without dark adaption I could see a faint red glow in the sky above me (through the rare gaps in the trees; they’re still leafed out here and I live in the middle of a forest). I took a few shots, lost my mind for a few minutes, then got my wife outside to see. We then waited until about 11:30 for the Moon to set before heading out in the car to find a spot with more sky. We found one, and I took a bunch of shots like those above.

When we got home I went onto the deck in our back yard because I knew something cool: the Andromeda Galaxy was almost directly overhead. That meant I could rest my camera facing up and just take a bunch of photos. I think this one, using the 0.6X wide-angle lens, showed it well:

The galaxy is the fuzzy smear dead center. The Pleiades star cluster in Taurus is at the top, and the Milky Way streaks across the shot, too. That’s my house on the right. I wish I could’ve stayed awake a couple more hours to get Orion up high enough to see as well. I’m not sure the storm lasted that long, though; by Friday it had subsided.

Now look, I’m an astronomer with a lot of experience watching the sky. I’ve seen a whole pile of stuff that I still shake my head in wonder about; a rocket booster re-entering like a Hollywood movie asteroid, several supernovae, eclipses, transits of Venus, a fireball bright enough to leave an afterimage on my retina, and more.

But I’d never seen an aurora until last night. Well, not fully; I glimpsed one when my daughter was very little, but it was a kinda sorta red glow in a small hole in the clouds. I saw a couple of faint patches near the horizon visiting White Horse, Yukon, but I can’t be sure those weren’t distant clouds.

And here we are finally, with the Sun getting near the peak of its magnetic cycle with enormous sunspots and powerful solar storms. There’ll be more chances, I bet.

But hopefully nothing too big. The Sun blew off a truly immense solar storm in 2012 that, had it hit us, would have been very, VERY bad. Like, technological-civilization-ending bad. I’m always amazed at how little coverage this got at the time. It really was that huge. It would’ve blown out power grids and damaged a lot of satellites; the magnetic of a truly colossal CME can shake Earth’s magnetic field, creating big currents of electricity under the ground that can then overwhelm transmission lines and transformers. That happened in Quebec in 1989, causing widespread blackouts. The storm of 2012 was way bigger than that one.

We may yet see one like that this solar cycle, and hopefully, again, it’ll miss. The Earth isn’t a huge target, but CMEs can be pretty wide. The last big one to hit us was in 1859, and the clock is ticking.

The aurorae are incredibly beautiful, magical to our senses, but they are also a warning that much more powerful forces are at play. We need to take that very seriously indeed. 

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