The Zodiacal Light

by | 10 Mar, 2023 | Astronomy, Landscape, Nature, Photography, Travel | 0 comments

Last spring, and the one before that, I spent a number of nights on high hills looking west. I could hear Redwings above me, their thin calls raining down as they journeyed back to Scandinavia. I was looking for the zodiacal light, a faint glow created by sunlight reflecting off dust particles in the inner solar system. Scientists think this dust originated on Mars, swept so high during fierce dust storms that it escaped the Martian atmosphere. It’s a vast area, reaching up like an upside-down cone from the western horizon (or eastern in the autumn). From the UK, it is best seen just after twilight in the months around the spring equinox, or just before dawn around the autumn equinox, but the sky needs to be dark. Light pollution really hampers your chances of seeing it. Known as ‘false dusk’ and ‘false dawn’ respectively, in dark skies it can be bright enough to fool observers into thinking it’s the light from the Sun. It follows the ecliptic, which is the path taken by the Sun, Moon and planets through the sky, a path which is at its steepest angle on spring evenings and autumn mornings.

Although I have tried to see the zodiacal light multiple times, I’ve been thwarted by my location. Looking west from this part of Devon means looking towards towns and cities, and towns and cities create light pollution. I also suspect I wasn’t high up enough. I could have done with higher hills and fewer lights. The brightest part of the zodiacal light is near to the horizon, so the higher you can get with a clear view of a (dark) horizon, the better. Not the easiest thing to do near here. 

But there was hope. Back in March 2017, my friend Simon and I travelled to Knoydart, a difficult to reach peninsular in Lochaber, Scotland. Unless you have a helicopter, it can only be reached via a ferry, chaperoned by Harbour Porpoises, or a sixteen mile walk across rough, mountainous terrain. It has a small community of just under a hundred people, and it is home to Britain’s most remote mainland pub, The Old Forge, which encourages people, delightfully, to ‘come away in’. 

Knoydart path, Scotland.

Simon and I took the ferry and camped at Long Beach campsite, overlooking Inverie Bay. This heads out westward towards Mallaig and the Aird of Sleat on the Isle of Skye and beyond that, the Isle of Rum. We walked a long way in the few days we were there, into the hills beyond Loch an Dubh and up Ladhar Bheinn, Knoydart’s highest peak. Down in the valleys it was warm, exceptionally so for March, but in places the mountain peaks still held their thick, royal icing layer of snow, bright white under cirrus-streaked, azure sky.

Ladhar Bheinn, Knoydart, Scotland

Before we bedded down in our tents that first night, I took my camera and tripod down to the water’s edge and attempted to take a few photographs of the stars, but I was tired and my photographs suffered as a result. I was also frustrated by what appeared to be light pollution. I had thought there wouldn’t be any light pollution in such a remote spot, yet I was definitely seeing something bright which veiled the stars. Shortly after, and somewhat annoyed, I packed my photography kit away and climbed into my sleeping bag.

That night was cold; the day’s warmth evaporated instantly. Having already collapsed on me somewhere along the West Coast, my faulty one man tent did little to redeem itself during our first night at Long Beach. Waking up in the morning, I found it had crumpled in on itself again, and was covered in frost. I was chilled to the bone. I tried to find some residual heat in the depths of my sleeping bag, but all traces of it had dispersed during the night. I unzipped my tent and looked out across the bay. The still water carried the rosy reflection of the Belt of Venus, and a thin layer of frost clung to the pebbles on the shore. Slowly, as the Earth turned, the distant peaks of Rum turned red, and Little Ringed Plovers foraged along the strand. I was struck by the tranquility of it all. It is rare for the weather in Scotland to be so calm, but when it is, the landscape seems to stretch on for aeons. Ancient water laps against ancient rock and the sky, that same sky we all see, feels older somehow. 

Belt of Venus above Inverie Bay, Knoydart, Scotland

Years later, in 2022, I was idly scrolling through photographs from our trip. As I reached my astrophotography attempts I realised I’d made a mistake. It was not light pollution I had seen that night. It was the zodiacal light. There is was, a little faint but visible, reaching in from the right-hand side of my photographs up towards The Seven Sisters of Pleiades and beyond. A vast pillar of silvery dust projected across the sky. My photograph of it is, by professional astrophotography standards, poor. But the quality of my photograph doesn’t matter. What matters is that, while stood on Earth, I have seen sunlit Martian dust (combined, perhaps, with asteroid and comet particles) and, even if I did confuse it for light pollution at the time, that’s quite a phenomenon to have seen.

Zodiacal Light above Inverie Bay, Knoydart, Scotland

My next target will be the gegenschein, a patch of interplanetary dust directly opposite the Sun in an area of sky known as the antisolar point. But to see this, I’m going to have to go somewhere very, very dark…