Here in the Canadian Rockies, I consider prime night-photography season to extend from September until January. The later winter is often stormy, the spring is definitely stormy, and mid-summer is so bright that night sky here is only really dark for a couple of hours. In September, the core of the Milky Way is as visible as it gets this far north, the summer haze has usually cleared out of the sky, and temperatures are still comfortable.
When a clear weather window opens up in late September, my friend Arie and I excitedly discuss possible locations for the first night photo session of the season. We are looking for excellent dark skies, a spectacular view to the south to capture the Milky Way, and also relatively easy access because we can not afford to stay out overnight. Surprisingly, while the internet is drowning in daytime photos of Moraine lake, there are not very many night photos – so we agree that it is a worthy destination for this weather window.
Moraine Lake is likely the most famous view in Banff National Park, for good reason!
The famously blue/green water is surrounded by lush forest and guarded by a towering wall of jagged peaks. This spectacular lake is exactly what you imagine a high mountain lake should look like. Well known among tourists the world over, its beauty was etched on to the back of the Canadian $20 bill from 1970 until 1993.
The classic view is from the “rock pile” formed by the landslide that dammed the valley and created the lake. The rock pile is just a five-minute walk from the end of the road, guaranteeing 1000s of visitors and 1000s of photos a day, all pretty much the same, give or take the weather and a few meters difference in perspective.
During the summer months, the only access to Moraine Lake is via a shuttle bus that ferries visitors up and down the 10km road, from morning until night. The parking lot at the lake was open to private vehicles (until October 2022), but no vehicles are allowed up the road once the lot has filled – which happens before dawn. And the lot doesn’t clear out until after sunset, which means that even on a Tuesday in late September we are not able to drive there until after 8pm.
Update, January 2023: The Moraine Lake access road is closed to private cars year-round. In the summer months, you can take the shuttle bus, or the Roam bus, or ride a bike. In the winter the road is track-set for cross-country skiing.
A quick hike to Mud lake
We get to Lake Louise in the late afternoon, go for a quick little hike to the boringly-named Mud Lake, across the highway to the north of town. It’s a nice stroll through the forest, and the lake turns out to be much prettier than its name suggests, forming a beautiful mirror for the big peaks of the Louise group across the Bow Valley.
After the little hike, we head to start of the Moraine lake road, where there’s a small picnic area. We hang out there, warming up dinner over a camp stove while waiting for the sky to darken and more importantly, for the Moraine lake road to open.
Finally getting to Moraine lake just after 8pm, we walk in with headlamps under the rapidly darkening sky, and are pleasantly surprised to discover only a few groups wandering about the famous rock pile viewpoint. We scope out a good location, needing a clear view of the lake and peaks to the south, as well as a view to the north to align the star-tracker, and set up the tripods and camera gear. By now the sky is quite dark, the brightest stars are out, and the sky is still brilliantly clear.
As the sky continues to darken, the Milky Way stars to appear as a faint hazy band, moving slowly from east to west, and by around 9:30 it has moved nicely into position, directly behind the peaks behind the lake. I start capturing the grid of 20 long-exposure frames that make up this image, while chatting with other photographers who have setup nearby. A surprisingly social evening for what it usually a pretty solitary hobby! Each frame is exposed for 120 seconds at ISO 800 using a 50mm lens at f/4.
Zoom in and explore this high resolution image.
There are an incredible number of cosmic gems to see in this part of the sky, and understanding what we are seeing here has driven astronomy and physics research for 100s of years.
Seeing the Milky Way
To the naked eye under really dark skies, the Milky Way appears as a band of bright haze, mottled with dark patches, arcing across the night sky. The bright clouds are millions of stars, too far away and densely packed to resolve without a telescope.
This glorious sight is only visible under very dark skies, which unfortunately is ever-more difficult to find, due to the scourge of light pollution. And light pollution doesn’t just bother astronomers and night photographers, but has adverse affects on human health, disrupts the behaviour and health of animals, and wastes a tremendous amount of energy.
I feel incredibly fortunate to be able to get to dark skies and marvel at this sight – the gorgeous lake and stunning peaks, covered in a dusting of fresh snow, with the countless millions of stars shining above.
These night photo sessions are rare and absolute magic for me. Due to unstable mountain weather, the phase of the moon, personal schedules, frigid winters and bright summers, I only get the opportunity to get out and photograph brilliant dark skies two or three nights a year. But every single time, the spectacle of the night sky fills me with an overwhelming sense of awe and wonder!
Structure of the Milky Way
Humanity has been observing the Milky Way for 1000s of years and the true nature of this hazy band crossing the night sky has been a mystery for most of that time. The invention of the telescope in the 1600s resolved the haze of the Milky Way into a myriad of stars, but not until the mid-1700s was the essence of it proposed: we are seeing an inconceivably vast disk of dust and stars from the inside, because our Sun is only one of the billions of stars that make up this galaxy.
We now know that our Milky Way galaxy consists of around 200 billion stars, immense clouds of cold dust and gas, hot, glowing nebulae that are actively creating new stars, and a super-massive black hole at the centre around which everything rotates. Ours is a barred spiral galaxy, with two (or four?) major arms of stars that spiral their way out from the core. Between the major arms are at least four minor arms, and our Sun is located about 2/3 of way from the core, on the edge of the minor Orion arm of stars.
Determining the structure of the Milky Way is very difficult; imagine trying to make a map of your home if you can’t leave the kitchen. In the case of the galaxy, the view in many directions is blocked by dark gas clouds, and it is so incredibly large that we can’t, and likely never will, get a view of it from the outside.
The basic technique used by astronomers to map the structure of our galaxy is to map the locations and distances of gas and stars, then plot them on a 3D chart. The locations of the arms then reveal themselves as bands of greater density. This requires extensive star surveys, and many have been undertaken over the years, with the largest and most recent being the ongoing ESA Gaia satellite mission, launched in 2013. So far (winter 2023) Gaia has mapped the locations, distances (using parallax) and velocities of nearly 1.5 billion stars.
This image is an artists rendering – nobody has ever seen our galaxy from the outside! – that was produced from stellar survey data and represents astronomers best understanding of what our home galaxy looks like from above.
The structure of the Milky Way is very much an active area of astronomical research. While the overall shape is known to be a “barred spiral” – the core of the galaxy an elongated bar of older stars, with arms of younger stars spiralling outward from this centre – recent research suggests four major spiral arms rather than two. This excellent article details some recent research as well as summarizing some of the techniques used to map our galaxy.
In late September, the core of the Milky Way is in the southern sky, moving and setting to the west as the night progresses. The actual centre of the galaxy is not visible in the Moraine lake image, as it is below the wall of peaks, hidden behind Mt. Perren and Mt. Allen.
Note that the “bright pie” in the Milky Way diagram, showing roughly what is visible in the Moraine Lake image, only contains about 5% of our galaxy! Millions and millions of stars and yet it is only a tiny fraction of our galaxy.
Dominating the centre of the image is a great dark band flowing across the centre of the Milky Way. It appears as a vast dark cloud, obscuring the millions of stars behind it, and that is exactly what it is.
The Great Rift is a vast cloud of cold, primordial gas (mostly hydrogen) and dust (heavier elements) that is 1000s of light-years long, and thick enough to block the light of the stars behind it. It contains an estimated 1 million Suns worth of mass, material that will eventually fuel many future generations of stars.
Nebulae and star clusters
M16 Eagle Nebula
Barely visible above Mt. Allen is the Eagle nebula, Messier 16, made famous by the Hubble space telescope Pillars of Creation image in 1995. In almost 30 years of producing amazing images, this Hubble image is still one of the most iconic, triggering genuine awe in millions of people around the world as it reveals the birthplace of stars, as well as the unbelievable scale of the Universe.
Just over 27 years later, the James Webb space telescope team released a fantastic new Pillars of Creation image, showing the massive dust columns as seen in infrared light.
And massive does not even come close to the scale of these structures. Each of the pillars is 4-5 light-years long, with one light-year being 9.5 trillion kilometres. In our history of space exploration, there are currently only five spacecraft that are leaving our solar system, sailing through interstellar space. The fastest of these is Voyager 1, launched in 1977, and traveling not quite 17 km/second (that’s 61,200 km/h!). At that speed it would take over 70,000 years (!) to travel the length of one of these dust pillars, which by coincidence is roughly the distance to the nearest star.
In the James Webb image at right, note the bright red orbs and specs at the tips of four of the large pillars – these are knots of gas that are dense enough to be collapsing under their own gravity, getting warm (and bright in infrared light), and forming stars and planets. We are seeing the creation of new stars and planets!
This image is extremely high resolution – over 200 megapixels – and well worth downloading from the Webb telescope site and exploring.
And these enormous pillars are only a portion of the Eagle Nebula. The wider-field ESO image, taken in visible light, shows the full nebula, including the brilliant cluster of newly-formed stars above and right of the famous pillars. These very young, giant stars are pouring out tremendous amounts of light and radiation – 100,000s times more than our Sun – and that torrent of radiation is what has created the pillars by eroding away the surrounding gas and dust.
North America nebula
At the top-left of the Moraine Lake image, just left of the bright star Deneb in Cygnus, is an enormous cloud of glowing red hydrogen gas: the vast North America / Pelican nebula. From our perspective it spans about 3 degrees of sky, appearing more than 10x the area of the full moon, but like most nebula is not visible to the naked eye. At a distance of around 2590 light-years 3 degrees of arc means that its actual size is about 140 light-years wide.
As revealed in this stunning portrait, the North America nebula (on the left) and the Pelican nebula (at lower-right) are actually the same glowing gas cloud, bisected by a dark swath of gas. Unlike M16, there are no bright stars visible in this nebula, and the source of the ionizing radiation that causes the gas to glow was a mystery until infrared studies revealed the source of that energy to be a single giant star, obscured from our view by the dark cloud that bisects the nebula.
Zooming in to the “Mexican coast” region of the nebula – where the dark bulge at the lower-centre is the Gulf of Mexico – shows the incredible complexity of the Cygnus Wall region. The dust clouds are being compressed and eroded by the torrent of light pouring out of the (hidden) star that is lighting up the whole nebula, and within the compressed knots of dust, new stars and planets are being formed.
These nebulae, and most others, are both forming and being formed by the stars they are creating. Once the giant stars ignite, they blow away the surrounding dust and gas, creating the vast cavities, walls and pillars. The remaining hydrogen is ionized by the intense UV light of the stars, causing it to glow red, and other portions of nebula shine blue with reflected light of the star, and also blue from ionized oxygen.
What remains after the dust has been blown away are clusters of young stars, still bound together by gravity.
Most of the star clusters in the Milky Way are therefore relatively young, meaning 10s to 100s of millions of years. This is young compared to the lifespan of stars, which is often billions of years: our Sun is roughly 4.6 billion years old.
When a group of stars is born in a collapsing dust cloud, all manner of different sized objects are also formed. Small rocky objects like asteroids, moons and small planets like Mars and Earth, giant gas planets like Jupiter and Saturn, and brown dwarfs that are many times Jupiter’s mass but still too small to initiate hydrogen fusion. But in a new-born solar system, the star collects by far most of the mass of the collapsing dust cloud – in our case, the Sun makes up 99.86% of the total mass of the solar system. The stars that form vary in size from small, cool stars (10% the mass of our Sun) to medium-sized stars like our Sun, to giant stars 50 or more times the Sun’s mass and 1000s of times as luminous.
Eventually, a star cluster drifts apart and dissipates with time, as their small and medium-size stars are ejected by gravitational interactions with their stellar siblings. The largest stars in the cluster don’t live long enough for see that, as their short, brilliant lives end explosively as supernovae. Eventually, after 100s of millions of years, most star clusters have broken apart, their stars now drifting freely among the billions of others in the galaxy.
The lifespan and fate of a star is (nearly) completely determined by its mass at birth.
Small stars, with around 10% of our Sun’s mass, are called red dwarfs. They consume their hydrogen very slowly, glow dimly with a red light, and will do so for 100s of billions of years. Medium-size stars, like our Sun, fuse their hydrogen to helium more quickly, shine with a more yellow light, and have enough hydrogen to shine steadily for around 9 billion years. Our Sun is about halfway through its life, and in another 5 billion years it will run out of hydrogen, expand dramatically, likely enveloping Venus, cooking Earth to a cinder, and becoming a red giant star that is 100x larger than today and shines 1000x brighter. After more than 100 million years and several phases of expansion and contraction, it will blow off about half of its mass, becoming a brilliant, tiny white dwarf star at the centre of an expanding cloud of debris.
The material blown off by a dying star of the Sun’s mass forms a planetary nebula: a vast shell of gas expanding out into space, with a white dwarf at its centre, the core of the dead star. There are two famous examples of these in the Moraine lake image. M27, the Dumbbell nebula, is just above the constellation of Sagitta while M57, the Ring nebula, is in Lyra, a small constellation anchored by the brilliant star Vega.
These expanding gas clouds are called planetary nebula because they are usually round and colourful, looking like planets through early and small telescopes.
When a star has more than 10x our Sun’s mass, the intense gravitational pressure in their core causes very rapid fusion of hydrogen to helium, resulting in extremely hot, bright stars shining white or blue-white, that only live for a few 10s of millions of years. Deneb, the very bright star at the tail of Cygnus, is a supergiant star, about 200x the size of our Sun and putting out an estimated 200,000x as much light.
When these giant stars run out of hydrogen, their core collapses suddenly to an inconceivably dense sphere, the outer layers of the star fall inward, and then rebound off the core as a supernova explosion. These explosions are among the most violent events in the Universe, and for a brief time the exploding star is as bright as an entire galaxy.
The explosion blasts the outer portions of the star into space at 100s of kilometres per second, forming a vast, expanding cloud of debris. The Veil Nebula, visible but very dim on the left side of Cygnus the Swan, is the thin and diffuse shell of a supernova that exploded between 10,000 and 20,000 years ago. Based on Hubble images taken 18 years apart, the Veil nebula is expanding at around 1.5 million km/h, over 400 km/second.
There are a handful of bright globular clusters visible in this image: M10, M12 and M14, all in the constellation of Ophiuchus, plus M56 in Lyra and M71 in Sagitta.
Compared to the relatively young star clusters that reside within the disk of the Milky Way, globular clusters are very different in several ways.
Age: globular clusters are billions of years old, making them some of the most ancient structures in the universe. Regular star clusters are usually 10s to 100s of millions of years old.
Size: globular clusters contain 10,000s to millions of stars, making them 100s of times larger than regular star clusters.
Location: globular clusters are found in wide-ranging orbits that swing far from the disk of spiral galaxies, whereas all regular star clusters orbit within the disk of the galaxy.
Distance: globular clusters are much further away, usually between 20,000 and 50,000 light-years, while most visible young star clusters are only a few 1000 light-years away.
Shape: because globular clusters are so large, and mostly outside of the galaxies disk, they are able to maintain a roughly spherical shape, whereas star clusters have irregular shapes.
Back on Earth
Mountains have always filled me with a sense of wonder and awe; grand and majestic, beautiful, dangerous and ancient.
But mountains are grand on a human scale; most mountains in the Canadian Rockies can be climbed in a few days, and whole ranges can be traversed in mere weeks under human power.
But the Universe is grand and majestic on a scale that is incomprehensible to us. The Milky Way, our home galaxy, surrounds and dwarfs anything and everything on Earth. And it is only one of billions of galaxies… The spectacle of those millions of stars, the knowledge of what’s out there, 100s of trillions of kilometres away, takes awe to an entirely new level.
It is awe on a cosmic level.
Visualize the reality: Earth, with everything and everyone we have seen and loved and known, is only a tiny, fragile blue globe, wrapped in an eggshell-thick atmosphere, floating alone in harsh vacuum.
This is our only home in the infinite vastness of space.
Let’s take care of it like it’s the most precious thing we have… because it is.
– Darren Foltinek, January 2023