Nature, Landscape, and Night Sky Photography by Zach Schierl


Comet NEOWISE Appears in the Morning Sky

A comet with a bright nucleus and long tail appears in the pre-dawn sky.

Naked-eye comet alert! Comet C/2020 F3 (NEOWISE), discovered back in March, has brightened to the point where it is visible to the naked-eye in the pre-dawn sky. Both the comet and its tail were easily visible to the naked eye about one hour and fifteen minutes before sunrise this morning:

A comet with a bright nucleus and long tail appears in the pre-dawn sky.

Comet C/2020 F3 (NEOWISE) at 4:05 am PDT on July 8, 2020 from Yakima County, Washington. (Nikon D750, 260mm, f/5.6, ISO 400, 1.6 sec)

This is the first time in ~20 years of skywatching that I can recall seeing a comet and its tail with the naked eye. (Western Washington’s persistent clouds and 49°N latitude stymied my attempts to see Comet PANSTARRS in 2013.) Such comets are relatively uncommon, making it well worth the effort to get up to see this one.

Here’s how to see it yourself:

Look northeast 75-90 minutes before local sunrise. You’ll need a relatively clear horizon in that direction. For most locations in the United States, the comet will be no more than 10 degrees above the horizon at this time. A large tree 200 yards away was enough to block the view of the comet from my patio, forcing me to take a short stroll through the neighborhood to find a better vantage point. The comet is small, but for at least the next few mornings should be readily visible. Here’s a wide field view to give you a better sense of the comet’s apparent size:

A bright comet appears just over the horizon in the pre-dawn sky

Comet C/2020 F3 (NEOWISE) at 4:02 am PDT on July 8, 2020 from Yakima County, Washington. (Nikon D750, 70mm, f/2.8, ISO 400, 1 sec)

Timing is key. My experience is that the comet is best seen about 75-90 minutes before local sunrise. Too much earlier and the comet will be too low in the sky to see clearly. Too much later and the brightening dawn sky will render it invisible. This morning, by about one hour before sunrise, the comet had become much more difficult to pick out and the tail was barely visible to the naked eye. By 45 minutes prior to sunrise, the comet was no longer visible to the naked eye at all (although it was still visible in binoculars or a camera).

Since you’ll be observing in twilight, light pollution conditions shouldn’t make much of a difference here; this comet should be visible even from urban areas, provided you have a clear northeast horizon and time your attempt correctly. A pair of binoculars greatly enhances the view. For more detailed information on viewing Comet NEOWISE, check out

Now for a bit more on what you are seeing and how the comet’s appearance might change over the coming days and weeks: 

Comets are city-sized “dirty snowballs” made mostly of ice and rock. They are leftovers from the formation of our Solar System and orbit the Sun on highly elliptical paths. Comet NEOWISE takes several thousand years to complete one orbit of the Sun. While comets spend most of their time in the cold outer solar system, when they approach the Sun they are heated by solar radiation, causing ices on the comet to begin sublimating (turning from a solid into a gas). This creates a temporary atmosphere surrounding the comet nucleus known as the coma. That’s the bright part of the comet you see in the close-up below. A stream of ionized gas “blown” off the comet by the solar wind can form a tail, while dust particles left behind the comet can form a second tail. As you can see in the close-up, Comet NEOWISE does appear to have two distinct tails at the moment.

Close-up view of a comet with a bright nucleus and a two-pronged tail

A close up of the coma and twin tails of Comet C/2020 F3 (NEOWISE).

NEOWISE made its closest approach to the Sun back on July 3rd and is now on its way back into the outer solar system. Typically, as comets move away from the Sun’s heat, they dim. So far though, NEOWISE appears to be bucking the trend. This is exciting because while the comet is moving away from the Sun, it is moving closer to us. It will reach its closest point to Earth by about July 22nd. If the comet can maintain its brightness for just another week or two, the show could get even better. Now is still the time to look though. The comet will be visible in the morning sky for just a few more days before it disappears into morning twilight. It will reappear in the evening sky by mid-July. Here’s hoping it is still bright enough to see by then. If so, we can all enjoy its presence without having to get up at 3:30 AM!

Colorful Geology at Valley of Fire State Park

Compaction bands and sandstone, Valley of Fire, Nevada

Compaction bands in multi-colored Aztec Sandstone, just one of many geologic wonders in Valley of Fire State Park, Nevada

One of the great things about living in Southern Utah is the abundance of different climates within a small geographic area. When temperatures rise into the 90s and 100s in the low-elevation valleys, we can be in cool alpine meadows at 10,500′ in less than an hour. When snow, slush, and mud cover the trails in winter, vast portions of the Mojave and Great Basin Deserts are within a day’s drive. One of these desert areas is Valley of Fire State Park in southern Nevada, not far from I-15 between St. George and Las Vegas.

Perhaps not surprisingly, upon arrival at Valley of Fire one is greeted with an array of whimsically sculpted red rock formations. Now red rocks are hardly unique in this part of the country, and the crimson cliffs here are no more notable than those found anywhere else in Utah or Arizona. But head into the interior of the park and you soon realize the allure of the Valley of Fire. After cresting the red cliffs, the hues begin to multiply exponentially and before long you are surrounded by just about every color of sandstone imaginable.

Colorful rocks at Valley of Fire State Park, Nevasa

A layer-cake of spectacular colors in Valley of Fire State Park, Nevada

To put it bluntly, the colors at Valley of Fire are simply ridiculous…and attributable to its unique geologic location. The rocks here are mostly equivalent to those found throughout southwestern Utah and the Colorado Plateau. The Aztec Sandstone, the dominant rock unit exposed in the park, is the equivalent of the Navajo Sandstone that makes up the cliffs of Zion National Park. Geologists just assign it a different name when it appears in Nevada and the Great Basin. Perhaps the distinct name is appropriate though, given that the sandstone seems to take on a life of its own here.

Valley of Fire State Park lies within the Basin and Range province, a vast region covering Nevada and portions of half a dozen other western states where the Earth’s crust is being slowly but violently stretched apart. As the writer John McPhee once noted, so much stretching has occurred here that 20 million years ago, Salt Lake City and Reno would have been more than 60 miles closer together. Faults are abundant in this land, and fluids associated with some of these faults have at various times leached iron compounds from the originally all-red sandstone, causing some layers to become bright white, and re-deposited them in other layers, leading to the wide variety of colors.

Some of the most impressive colors are found just to the west of the “Fire Wave” feature near the northern terminus of the park’s scenic drive:

Vibrant colors in the Aztec Sandstone in Valley of Fire State Park, Nevada

Vibrant colors in the Aztec Sandstone in Valley of Fire State Park, Nevada

Fire Wave in Valley of Fire State Park, Nevada

A feature known as the “Fire Wave,” Valley of Fire State Park, Nevada

While there are numerous hiking trails, there is also lots of off-trail terrain to explore. Some of the most spectacular scenery can be found by parking at one of the numerous pull offs and just wandering out into the rock wonderland. One particular geologic feature of note is what are known as “shear-enhanced compaction bands,” thin brittle fins of rock that rise almost vertically out of the ground and often run continuously for dozens to hundreds of yards. At first glance, these features look like mineral veins, but upon closer examination they are composed of the same material as the surrounding sandstone, but are obviously slightly harder than the host rock. In many places there are two perpendicular sets of the bands, forming a checkerboard like pattern superimposed on the sandstone.

Compaction bands in the Aztec Sandstone, Valley of Fire State Park, Nevada

Compaction bands in the Aztec Sandstone, Valley of Fire State Park, Nevada

The bands are the result not of stretching, but of compressional forces that predate the formation of the Basin and Range. Stresses associated with an earlier mountain building episode (known as the Sevier orogeny) created these funky bands by essentially “squeezing” together (and even breaking) the sand grains that make up the rock, eliminating much of the empty space between the grains and forming a miniature layer of tougher, harder, and more compact sandstone that is slightly more resistant to weathering and erosion. As a result, the bands tend to just out from the surrounding slickrock by several inches, and even several feet in some locations. For such a seemingly obscure feature, many papers have been written about these compaction bands (and similar ones in a few other locations in the region). However my understanding of the structural processes behind their formation is limited and the most recent articles about them appear to be behind a paywall. If anyone reading this has more insight into these things, I would love to hear from you.

As mentioned before, these bands are quite thin, in most less than a centimeter thick and thus, sadly, quite brittle. They are easily broken by an errant boot step so if you find yourself among them, tread carefully so that future visitors will be able to experience this unique and colorful landscape.

Colorful sunset on red rocks, Valley of Fire State Park, Nevada

Sunset from the Old Arrowhead Road in Valley of Fire State Park, Nevada



(Petrified) Forests of Stone

Close-up of log of petrified wood
Close-up of log of petrified wood

Despite being comprised almost entirely of quartz, trace amounts of elements like iron and manganese give petrified wood its myriad of colors.

I grew up about 90 minutes away from Petrified Forest National Park and, aside for a quick lunch stop about 10 years ago, had never visited before last week. While this is nowhere near as inexcusable as living in Arizona for decades and never visiting the Grand Canyon (yes, such individuals exist…I’ve met many), it still seemed like a bit of an oversight on my part. Or it could simply be a reflection of the inordinate number of outdoor activities that exist in northern Arizona; even living in the area for 10+ years isn’t enough time to hit everything. Either way, after finally venturing into the Petrified Forest, I can emphatically say that it should be mentioned with the best that northern Arizona has to offer.

Located amongst the vast Painted Desert of northeastern Arizona, the main attraction of Petrified Forest is of course the petrified wood. The formation of petrified wood is initiated when downed trees are quickly buried by sediment. Once entombed in the sediment, the lack of oxygen prevents the logs from decaying as they normally would when exposed directly to the atmosphere. In this case, the logs (none of which remain standing, despite the name “Petrified Forest”) were likely brought here in massive logjams along an ancient river system that existed during the Triassic period. A combination of sediment from the river and ash from nearby volcanoes buried the logs, not to be seen again for more than 200 million years. During this time, as the logs became buried under an increasingly deep pile of overlying sediment, dissolved silica began to crystallize in the pore spaces of the wood as quartz, eventually replacing all of the organic material while maintaining the original shape and structure of the log.

Brilliantly colored petrified wood fragment

A brilliantly colored petrified wood fragment.

Petrified wood is not particularly rare. Good examples abound in Yellowstone National Park, Washington state, Utah, Colorado, Oregon, Alberta, New Zealand…the list goes on and on. What makes Petrified Forest National Park unique is the quantities found here. Due to the aforementioned Triassic log jams, large quantities of wood were concentrated in small areas. In a location known today as Jasper Forest (see photos below), movement was not possible without walking over a nearly uniform carpeting of small petrified wood fragments and frequently having to clamber over 2-3 foot diameter logs. Truly stunning!

Petrified wood in the Jasper Forest

Petrified wood in the Jasper Forest, Petrified Forest National Park.

Overlooking the Jasper Forest at sunset.

Overlooking the Jasper Forest at sunset.

Another unique aspect of Petrified Forest is the colorful canvas on which the wood is found. The wood is eroding out of a rock unit known as the Chinle Formation, which essentially consists of all of the river sediment and volcanic ash the buried the trees in the first place. More than 1000 feet thick in the park, the Chinle Formation is composed primarily of extremely soft mudstones, clays, and volcanic ash. Water is able to easily sculpt the soft rock into fantastically colored and oddly shaped badlands that make a spectacular backdrop for the logs.

Chinle badlands

The soft muds and clays of the Chinle Formation are easily eroded, forming badlands-like topography throughout the Painted Desert.

Colorful badlands in the Chinle Formation

Colorful badlands in the Chinle Formation at Blue Mesa.

Petrified Forest National Park faces an issue not encountered by most other national parks, namely, the wholesale theft of the very resource it was established to protect. For this reason, the park is only open during daylight hours (from 8-5 in the winter) to minimize opportunities for looting. It strike me as very sad that such measures are necessary. With a little geological perspective, it becomes clear how incredibly lucky we are to experience a landscape like Petrified Forest at this moment in time. So easily eroded is the Chinle Formation that in many locations, several inches of it are removed each year. This may not sound like much, but geologically speaking, that’s a veritable bullet train of erosion. While it took tens of millions of years for the Chinle to be deposited, it will be erased from our planet by the unceasing forces of weathering and erosion in a tiny fraction of that. The petrified logs, being comprised mostly of silica, are harder and will last a little longer, but are still brittle and will eventually be washed into the Little Colorado River and swept downstream along with the colorful Chinle badlands.

What all this means is that the colorful Painted Desert/Petrified Forest landscape we see today is one that is extremely temporary. While this is true of most landscapes we see on Earth today—our planet likes to re-build, re-arrange, re-shape, and remove constantly—the Painted Desert is even more ephemeral than most. While mountain ranges comprised of harder, erosion-resistant granite or quartzite (like most of the Rockies) can stand the test of time to some degree, the longevity of the Painted Desert, its soft sediments, and its brittle petrified wood is comparatively brief. Stealing this treasured natural resource only abbreviates our time with the Petrified Forest even more.

Petrified wood in the Chinle Formation

Pieces of petrified wood accumulate in small hollows in the extensively gullied Chinle Formation.

Petrified logs in a small wash

The soft sediment surrounding the logs is easily transported away by small streams and washes.

Petrified wood and quartz on pedestals

Relatively hard chunks of petrified wood and quartz protect the softer sediment of the Chinle Formation from erosion, forming pedestals small…

Large piece of petrified wood in pedestal.

…and large!


Capturing Cosmic Dust with a Camera: the Zodiacal Light

Cameras can be strange machines. We tend to think of cameras as devices that faithfully record the nature of the landscape around us, which they do…at least most of the time. When this paradigm does break down, it is usually because the camera has failed to record something important, something that made a moment or an experience worth remembering. Oftentimes when this happens, we become disappointed. How many times have you been scrolling through vacation photos and lamented at how poorly they turned out? Sometimes we even realize the limitations of the camera in the moment itself. Perhaps you’ve experienced something akin to standing on the rim of the Grand Canyon at sunset and becoming so resigned to the fact that no photograph will ever satisfactorily capture the grandeur in front of you that you begin to ponder the option of chucking your camera into the great chasm below.

On rare occasions though, the camera delights us by managing to capture even MORE than meets the eye. After returning from a recent camping trip to the San Juan Islands in northwest Washington, I was surprised to find an unexpected apparition in some of the long-exposure photographs I took from our campsite on the west coast of San Juan Island.

Getting to the San Juans is no easy task; it took me about 5 hours to get there, even though “there” is just 35 miles by air from my front doorstep. As a result, the islands can feel remote and isolated, but standing along the coast at night is a not so gentle reminder that you’re actually only about eight miles across the Haro Strait from Victoria, a metro area of more than 300,000 people. Taking advantage of a somewhat rare, perfectly clear Pacific Northwest evening, I took a series of 15 second exposures looking west across the strait which I composted into this 180 degree panorama:


Click photo to embiggen!

The first thing you notice is the egregious light pollution from Victoria. Even the skyglow from Vancouver, five times further away but seven times more populous, is visible through the tress. Amongst all of the artificial light sources though, some natural ones still manage to shine through. The faint tendrils of the winter Milky Way just barely register on the camera’s sensor but the bright winter constellations of Orion, Canis Major, and Taurus forcefully punch their way through. If you look really closely, you’ll see a faint, slightly elongated, pale blue glow hiding in-between the lights of Victoria and Sidney. This is a phenomenon known as the zodiacal light, and it’s what took me by surprise when I started putting these images together. Here’s an annotated version to help you out:


See it? It’s a slightly different color than the light domes and isn’t as round and symmetrical as the light radiating from the cities, but rather looks squished and creeps upward into the sky at an angle. What really betrays the nature of this mysterious glow is its location: it coincides almost perfectly with the ecliptic, the plane of our solar system which is also the apparent path that the Sun, Moon, and planets follow as they move across the night sky.

What does this have to do with the zodiacal light? Well, it turns out that the plane of our solar system is home to lots and lots of dust. Not the dust made of dead skin cells and carpet fuzz you find around your house, but rather interplanetary dust particles made mostly of carbon, silicon, and oxygen. These dust particles are really small, on the order of 10 micrometers in diameter, about the size of a mold spore. The exact source of this dust is controversial; most of it is thought to be the result of collisions between comets and asteroids although some may be leftover from the formation of the solar system itself, tiny pieces of debris that never got incorporated into a planet. Regardless of where it cam from, the dust is really good at reflecting sunlight. Just after sunset (or just prior to sunrise), the angle between the Sun, dust, and Earth is such that the light reflected of the surfaces of the innumerable dust particles reaches our eyes (or cameras) here on Earth, giving rise to the zodiacal light.

When you consider how small the dust is (and that the dust particles are on average more than 2 miles apart from one another!), it’s not hard to understand why the zodiacal light is so faint and difficult to spot. Due to a quirk of celestial geometry, spring is a great time to observe it from the northern hemisphere, but even then spotting it with the naked eye requires extremely dark skies. The conditions in the San Juans, while darker than many spots in Western Washington, are far too light polluted. However, digital cameras are MUCH more sensitive to faint sources of light than the human eye. It’s actually rather common for a camera to detect things in the night sky that aren’t visible otherwise. On the night I saw the aurora borealis for the first time about a year and a half ago, its presence was first betrayed to me as a faint green glow hugging the horizon on my camera’s LCD screen, hours before it became bright enough to see with the naked eye. If not for my camera’s ability to detect it, I would have been fast asleep instead of standing in a marshy field near the Canadian border when the aurora dramatically brightened a few hours later and streamers began appearing all over the sky.

Have you ever captured anything on camera that you found surprising? Share your thoughts or stories in the comments below.

Snails of a Different Color


Up until a few days ago, I would have felt extremely confident saying that I’ve seen more fossilized sea snails in my life than I have real ones. After all, teaching a lab that revolves around sedimentary rocks for two quarters will put one in close contact with more dead gastropods than one ever thought possible. And when you spend a lot of time staring at multi-million-year-old fossils, it’s often easy to forget that lots of the little buggers have closely related relatives still trolling the high seas today.DSC_8284Just a few of the many, many, MANY different colored and patterned varieties of nucella lamellosa, the Frilled Dogwinkle

A few days ago though, I stumbled upon a sea snail breeding ground of epic proportions at a place called Point Whitehorn Marine Reserve. I had gone there with the express purpose of looking at rocks and I remain convinced that the snails made their dramatic appearance in order to force me to confront the inherent irony in going to a marine reserve to look at rocks. Near the low-tide line, a couple of bright orange striped shells grabbed my attention, sticking out marine creamsicles amidst the backdrop of drab green algae and seaweed, dull brown barnacles, and grey sky reflected in the waves. I soon realized that I was surrounded (in a benign and not even remotely threatening way) by hundreds upon hundreds of sea snails exhibiting a dazzling array of different colors and patterns.

Now, my knowledge of sea snail taxonomy is limited, but it appears that despite the disparate appearance of these snails,  they are all part of the same species: nucella lamellosa, also known as the Frilled Dogwinkle or Frilled Whelk (if anyone has information to the contrary, please let me know). Most of the snails in these photos are smooth; they have lost their ridges or frills that normally run along the length of their shell. This is apparently a common fate of nucella lamellosa that choose to spend their lives in places like Pt. Whitehorn which experience very rough surf during the winter. The frills literally get worn away, not at all surprising when you consider that the shells are made out of calcium carbonate, a substance that in it’s crystalline form is only a we bit harder than drywall.


Purple was the rarest color I encountered; orange, black, grey, and pure white seemed to be the most prevalent.

Many rocks were encrusted with dozens of the snails, varying in size from babies barely larger than a pea, to a few gargantuan snails nearly four inches long. This species hatches in late winter and early spring, so this is a good time to get a sneak peak at the next generation. A female sea snail can apparently lay thousands of eggs each year, although like most species who opt for quantity over quality when it comes to reproduction, only a small percentage survive to adulthood. In the case of nucella lamellosa, that number is estimated at a paltry 1%. Upon reading this, I realized in horror that the occasional sharp “crunch” heard from underneath my boots while I was taking these photographs was nothing other than the sound of my contribution to this rather depressing and morbid statistic. But with any luck, those shell fragments I (inadvertently) created will get weathered, transported, buried, and fossilized, eventually re-surfacing in the collection of some enterprising geologist a few million years from now, a fate that can only be described as THE ultimate honor for any ambitious gastropod.


The only decent shot I got of the innards of these snails.


A handful of the less gaudy looking but substantially larger snails. The largest one here is almost three inches long.


A variety six-pack of nucella lamellosa munching on some barnacles.



Airglow: Denizen of the Dark Sky

I’ve been an astronomy nut ever since my parents gave me a small reflecting telescope for my 10th birthday. I located Saturn, complete with its too-good-to-be-true rings, within 10 minutes of setting it up for the first time, although my parents refused to believe me until they had a look for themselves. I majored in astronomy, own a telescope that barely fits in my car, and come to think of it, every “real” job I’ve ever had has involved astronomy. NASA’s Astronomy Picture of the Day has been my homepage for longer than I can remember.

Given my disposition towards both astronomy and photography, it seems superfluous to say that I’ve always enjoyed astrophotography.  Taking photographs of celestial objects presents a set of challenges not encountered by photographers who go home after the sun dips below the horizon, the majority of which revolve around the fact that most astronomical objects are rather dim, requiring long exposure times and extra equipment to capture.

Quite frequently I’ll get asked if I’ve ever seen any UFOs while gazing up at the sky. My standard response is that, while I’ve certainly seen a lot of weird *#&@ in the sky, I’ve yet to see anything that didn’t ultimately have a logical explanation, even if it took a little head-scratching to figure it out (high altitude weather balloons are the worst!).

A prime example of this occurred this past summer during a nighttime observing and photography session. I was attempting to get a 180 degree panorama of our home galaxy, the Milky Way, stretching across the summer night sky. I had my camera mounted on a tripod head that compensates for the rotation of the Earth, allowing me to take exposures several minutes in length while avoiding star trails in my images. It was dark and clear enough that I was able to get some good shots of the summer Milky Way and its complex and sinuous inky-black interstellar dust lanes, as well as some decent shots of some galaxies and nebulae through a telescope:

MIlkyWayThe Milky Way in the constellations of Scorpius and Sagittarius. This portion of the Milky Way is home to the nucleus of our galaxy, making the Milky Way appear brighter here than anywhere else in the sky.

Lagoon_NebulaThe Lagoon Nebula, also known as M8, a vast cloud of hydrogen gas giving birth to new stars. A “stellar nursery” as astronomers like to say.

While my shots of the galactic center in the southern sky were turning out well, as I began to pan my camera around to the east and then finally north, I noticed that faint but noticeable bands of diffuse red and green light were creeping into my image.


My immediate thought was sensor noise. The CCD chip on my old DSLR (a Nikon D70) had a habit of heating up during repeated long-exposures. This thermal radiation from the sensor manifested itself as a bright purple/pink haze occupying one corner of the photo, making any attempt at serious astrophotography futile. Perhaps something similar was happening here. I quickly ruled this out for a number of reasons. Most importantly, the apparition was showing itself only in photos taken towards the north, meaning that the source couldn’t be the camera, but rather something in the sky itself. The colors ruled out high clouds, and it wasn’t in the proper direction to be the result of artificial light pollution. The closest city of any significant size to the northeast was several hundred miles away.

Whatever it was, neither myself or any of my observing companions could see it with the naked eye.  A bit eerie perhaps, but not at all uncommon. Many astronomical phenomenon are too faint to see without long-exposure photographs. In fact, the first time I saw the aurora borealis, I captured it with my camera several hours before it became bright enough to see with the naked eye.

A auroral display was actually my second thought. What I was seeing in my photos definitely resembled one. Red and green are the colors produced by nitrogen and oxygen, the two primary components of our atmosphere, after being excited by collisions with magnetic particles brought to Earth by the solar wind. Most auroral displays consist of some combination of these two colors and what I was photographing appeared only in the northern sky which fit the theory to a tee.  Furthermore, the Sun had been especially active in the week or so prior. It was perfect except for one slight problem: I was in Colorado.

Auroras in Colorado are definitely not unheard of….but not exactly common either. One thing was certain: if an aurora HAD crept this far south, then the northern portions of the country would simultaneously be getting the show of a lifetime. A quick check of, the one stop shop for up-to-the minute aurora information, showed this was not the case. Strike two.

I actually didn’t figure this one out until many days later, when I inadvertently ran across an article about some Pacific Northwest photographers who had captured something called “airglow” in some photos of the Milky Way taken at Mt. Rainier around the same time. A momentary glance at their photos and I knew I had my answer.


Here’s the final panorama I produced. The airglow (red and green splotches at left) was changing rapidly enough that it caused major headaches trying to stitch the images together. Consequently I didn’t quite get my 180 degree panorama, there’s a bit missing on the northern end (lower left).

Airglow is exactly what it sounds like (a rare thing in science, I know…): glowing air. Incoming solar radiation and cosmic rays ionize oxygen and nitrogen atoms in our atmosphere during the day and then then these atoms regain their electrons at night, emitting light in the process. This is similar to what happens during an aurora, except that it’s happening ALL THE TIME. Airglow is always there, it’s just really, really faint; you need to be somewhere extremely dark to have a chance of seeing it, even with a camera. Even a miniscule amount of light pollution will render it invisible. It does tend to be brighter when solar activity is high, although it is not nearly as dependent on the solar cycle as its brighter cousin, the aurora.

So what began as an unidentified and undesirable annoyance in my photos (and when trying to stitch together my panorama, boy it sure was!) turned out to be a rarely captured celestial phenomenon I had never even heard of, much less one that I had intended on photographing that evening.  Next time someone asks me about UFOs, I’ll just refer them to this page.