Noctilucent Clouds

I usually wake up and go walking at 3 or 4 a.m. (I go back to bed after…I just have trouble sleeping a whole night long for some reason and I like being up in the dark) and one morning in July as I was coming home, I looked out over the hill and saw such an interesting thing in the sky. It almost reminded me of the northern lights…something glowing and strange in the dark sky. But it was more defined and less shimmery than the northern lights. Just as I was thinking, "Hmm, what could that be?", my phone buzzed with a text from Seb, who works the night shift at the airport and so is also always up at 4 a.m.

He sent this picture with the caption "Super rare phenomenon!":

"I see it too!" I texted back. "But what IS it?" I'd already ruled out the aurora, and then I'd thought it might be the sunrise coming, but it was way too early for that!

Well. Of course. Leave it to Seb to know the most obscure astronomy facts. He sent me a link to an article called "Noctilucent clouds":

Noctilucent clouds may be seen at latitudes of 50° to 65°. They seldom occur at lower latitudes (although there have been sightings as far south as Paris, Utah, Italy, Turkey and Spain), and closer to the poles it does not get dark enough for the clouds to become visible. They occur during summer, from mid-May to mid-August in the northern hemisphere and between mid-November and mid-February in the southern hemisphere. They are very faint and tenuous, and may be observed only in twilight around sunrise and sunset when the clouds of the lower atmosphere are in shadow, but the noctilucent cloud is illuminated by the Sun. They are best seen when the Sun is between 6° and 16° below the horizon.…

Noctilucent clouds are thin, wispy clouds that glow with a blue or silvery hue at night when illuminated by sunlight from below the horizon. …In these months and at the right latitudes, the Sun only just sets below the horizon at nighttime. That means these very high clouds can still be lit by bright sunlight from below, even though the rest of the surface is in darkness – making the clouds appear to glow.

Noctilucent clouds are formed of ice crystals; in the summer the mesosphere becomes cold enough to allow ice to form on suspended dust particles floating in the atmosphere. The dust particles may originate from micrometeorites falling to Earth from space, or the dust left over from volcanic eruptions. Humans have also accidentally seeded our own noctilucent clouds through the exhausts of rockets propelled into space. The ice crystals that form reflect the sunlight when the Sun hits them from below, causing the clouds' characteristic shimmer.

Noctilucent clouds are beyond the shadow of a doubt the rarest and most mysterious we can observe from Earth. They are even less likely to be seen than northern lights!

Another of Seb's pictures, from his vantage point at work

So, to sum up if you didn't feel like reading that, they're just really really high clouds made of ice crystals, and you'd never usually see them because they're clear and the sunlight doesn't reach up that far, but near the solstice the angle of sunlight sometimes reaches up far enough to illuminate them a little before sunrise. But usually Utah is too far south (it says between latitude 50º and 65º, and Utah is only 40º), so I'm not sure why we were so lucky this time!

I immediately started reading everything I could find about noctilucent clouds because I was so curious about them! Seb and I were texting excitedly and nerdily back and forth for the next thirty minutes about them, and even submitted our photos to the "call for photos" from NASA science. I finally went inside but couldn't even go back to sleep because I was all excited about our discovery. I couldn't wait to tell Sam about it! I don't know quite why it was so exciting to me, but it just was! I felt the same both times after we saw the aurora—just kind of worked-up and elated about the whole experience.