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.
From the San Juans to the San Juans
They are separated by more than 1600 kilometers. One barely rises above sea level while the other boasts six peaks exceeding 14,000 feet in elevation. One is most easily accessed by kayak or porpoise, while in the other it is difficult to escape the incessant drone of Jeeps, dirt bikes, and ATVs that trawl the vast network of old mining roads. One is beset by a deluge of by rain eight months out of the year, whereas the other is inaccessible except by ski, snowshoe, or helicopter for six. To the untrained eye, the San Juan Islands of NW Washington and the San Juan Mountains of SW Colorado couldn’t be more different. My current job situation has me living about an hour away from the mountains for 3 months out of the year, and an hour or less away from the islands for the other 9 months. And viewed through the lens of a camera, I have discovered that there are more similarities that you might expect. The first of which will probably be rather obvious:
They both posses stunning scenery:
View from Deception Pass State Park on Fidalgo Island looking southwest across the water towards the Olympic Peninsula.
Rosy Paintbrush in an alpine meadow near Red Mountain #1 (yes, nearby can be found Red Mountain’s #2 and #3. The old miners were a creative bunch.) in the San Juan Mountains.
Both offer opportunities for “extreme” sports:
A paraglider enjoys a serene aerial view of the San Juan Islands and several tankers headed for the oil refineries in Anacortes, WA.
Descending a scree-filled colouir after summiting 14.150′ Mt. Sneffels in the San Juan Mountains. While most of the climb is straightforward and requires only a hefty amount of scrambling, there is one tricky section near the summit during which a fall would likely mean the end of one’s mountain climbing days…or any other days for that matter.
Both were shaped and sculpted by vast quantities of ice:
Glacial striations in slate high above the Uncompahgre Gorge in the San Juan Mountains. The parallel grooves in the rock were carved by rocky debris trapped along the base of a long-gone glacier that was partially responsible for scouring out the gorge.
A Washington State Ferry passes a cliff of glacially scoured rock in the San Juan Islands. Glacial striations identical to those in the previous photo are ubiquitous throughout the San Juan Islands, evidence that the area was buried beneath more than a mile of ice during the peak of the last glaciation, about 15,000 years ago.
And finally, both are home to curious wildlife:
An American Pika investigates a bush at 11,000 feet in the San Juan Mountains.
A Blood Star investigates a California mussel below sea level in the Strait of Juan de Fuca.
In case you didn’t know, that’s what starfish look like when they are curious.
Zach Schierl Photography 