After the normal mix of cold and stormy weather this winter, the magical conditions of a clear, high-pressure system, a dark moon, some free time, and non-frigid temperatures aligned near the end of February and I got out with my friend Arie for some some skiing and night photography.
Skiing around Bow Lake
The Icefields Parkway, running from Lake Louise to Jasper, accesses a vast amount of wild and remote backcountry terrain in the main ranges of the Rocky Mountains, along the east side of the Alberta / British Columbia border. After a late start, we get to the Bow Lake area in the afternoon, and manage to put in a couple quick laps on creamy early-spring snow on Observation Peak as the sun goes down. Next day we do a beautiful tour towards Crowfoot Pass, catching Crowfoot Peak in the early morning when it’s lit by the rising sun.
I love skiing (!), and the touring in this area is fantastic, but for me the main event of this quick trip was the opportunity to capture the pristine night sky far from civilization, catching a brief two-day window of clear skies, a relatively rare event in the usually stormy Rocky mountains.
Peyto Lake Viewpoint
The Peyto Lake viewpoint is one of the most famous views in Banff National park, and on a summer day you can barely see the lake for the tourists, but on this February night we have the place to ourselves.
Already in the parking lot, surrounded by forest, the sky above is thick with brilliant stars. It’s a short walk from the parking lot, and at the end of the trail the view is spectacular, with the lake below, Caldron Peak behind it, and the broad valley heading north. There are 1000s of stars visible, and arcing from north to south is the Milky Way, a stunning sight under these dark skies!
It takes about two hours to capture the 28 individual frames that are then stitched together to create the high-resolution mosaic image. There is no moon out tonight, and our eyes slowly adapt to the very dark night, but it doesn’t take long before we can see well enough to walk around in the snow and clearly see the lake and surrounding peaks, lit only by starlight.
Winter Milky Way over Peyto Lake, Banff National Park. Zoomable high resolution image: dive in.
The Milky Way
In the Peyto Lake image, the Milky Way is visible as the patchy band of stars starting at Cygnus (lower-right) and extending past Perseus at upper-left.
Here on Earth, in our solar system orbiting the sun, we reside about halfway from the center of the immense disk of stars, dust and gas that is the Milky Way galaxy. Like fish swimming in an ocean, who never gets to see their ocean home from above, we can never see our galactic home from the outside because it’s just too big for us to be able to travel outside and look back.
However, astronomers have been surveying the billions of stars in our galaxy for centuries, and together with observations of what other galaxies look like, have been able to assemble a fairly good picture of our galactic home.
This artists rendering shows the structure of our galaxy, and our location within it, as best we know today, based on stellar surveys including the VISTA telescope in Chile and the Gaia satellite, which is precisely mapping the location, distance, velocity, color and temperature of well over a billion stars in our galaxy.
As the Earth spins and orbits the sun, different parts of the Milky Way become visible at different times of year. In the northern hemisphere winter, the view north of the Milky Way looks outwards, away from the galactic center, through the fewest stars, and so we see the quietest part of the galaxy.
However, the quietest portion of a big galaxy is still a busy place, and this view of the northern sky includes countless thousands of stars, dozens of star clusters, several stunning nebula, as well as our two nearest galactic neighbors in deep space.
To the naked eye, under very dark skies, the Milky Way appears as a hazy (milky!) band of brightness arcing across the night sky. A long exposure image like this one reveals a wide variety of details in that milky band, including dozens of star clusters, several nebulae, and alternating dark and bright patches. The bright patches are the light of millions of unresolved distant stars, and the dark patches are clouds of dust and gas that block more distant starlight.
These dark, galactic gas clouds hold the potential for future solar systems, because when they are squeezed by a collision, passing shock wave, or gravitational disturbance, they can start to collapse, forming a new generation of stars.
After a galactic dust cloud collapses, during the first few million years the biggest and brightest stars light up and ionize the surrounding gas, causing it to glow as a bright nebula. However, tens of millions of years later, the biggest stars have blown away most of the remaining gas, and what is left is a group of 100s to 1000s of stars, all the same age, bound loosely to each other by gravity.
The Perseus Double Cluster, located between the constellations of Cassiopeia and Perseus, is a pair of relatively nearby (7500 light years) and young (13 million years) star clusters that each contain more than 300 bright blue super-giant stars. Under dark skies, they are visible to the naked eye and have been known since antiquity, and represent the jewels in the handle of Persues’ sword; stellar jewels indeed.
The famous Pleiades star cluster, seen in in the upper left of the zoomable image, is a beautiful example of an older, but still relatively young star cluster, about 100 million years old, that is lighting up surrounding galactic gas clouds. The cluster contains around 1000 stars, but only the largest, bright blue stars stand out from the background stars.
This stunning “Dusty Taurus”, image, built up from 2.5 hours of exposures by Amir Abolfath, clearly shows the dark galactic dust and gas that permeates this part of the Milky Way. The bright blue stars of the Pleiades, at upper-right, and the bright stars of the Hyades cluster, lower-center, illuminate the surrounding dust and gas, creating reflection nebula.
Most of the mass in stars and galactic gas clouds is hydrogen, created during the Big Bang that started everything. However, other, heavier elements are also present, and spectroscopic studies of star clusters have shown that the stars in a cluster have a unique chemical “fingerprint”, which reflects the amount and ratio of heavier elements present in the initial gas cloud that formed the stars, plus additional elements created by supernovae that occurred soon after the clusters birth.
After a star cluster has drifted apart over 100s of millions of years, these chemical fingerprints can be used to identify which of the billions of stars in the galaxy are long-lost “solar siblings” of our sun.
Star survey data gathered by the Gaia satellite project, which includes location, distance, velocity, brightness, and temperature of over a billion stars, has discovered a variety of new star clusters, and enabled spectacular 3D visualizations of what star clusters really look like.
GaiaSky visualizer: https://zah.uni-heidelberg.de/institutes/ari/gaia/outreach/gaiasky/
Our Milky Way is only one of billions of galaxies in the universe, and our little corner of this vastness contains a handful of galaxies called the Local Group.
Near is of course relative, and in space nothing is actually near, with the light from Andromeda taking just over 2 million years, and Triangulum taking 2.5 millions years, to reach us. At 300,000 kilometers per second, which is enough to go around the Earth 7.5 times per second, nothing moves faster. Even our solar system is so big that it takes light about 8 minutes to reach Earth from the Sun, 43 minutes to get to Jupiter, and 5.5 hours to get to Pluto. One light year is about 9.5 trillion kilometers, and the nearest star is over 4 light-years away, which is so far that it would take 10s of thousands of years for our fastest space probes, traveling 50,000 km/h, to get there. Good luck visualizing how far light travels in two million years…
Yet, you can see an object that far away under a clear dark sky with only your eyes!
Both of these galaxies can be seen by the naked eye under very dark skies, but the Andromeda galaxy is much bigger and brighter, and was first described by the Persian astronomer Abd al-Rahman al-Sufi in 964AD. In more modern times, in the early part of the 20th century, the size of the universe was not known, and there was much debate among astronomers about how far away “spiral nebula” such as Andromeda were. The debate was finally settled in 1925 when Edwin Hubble identified variable stars in Andromeda that were used to measure the distance, and therefore placed Andromeda many time further away than anything in the Milky Way. The Andromeda galaxy has similar mass, but contains about 1 trillion stars, which is about twice as many as our Milky Way.
The Triangulum galaxy is much smaller, with only 10% number of stars, and is only barely visible to the naked eye, and so was discovered in 1654, after the invention of the telescope. 10% of 400 billion is still a lot (!) of stars, and this galaxy is a very busy place, containing a wealth of bright red star-forming regions and young star clusters.
All the planets and asteroids orbit the sun in a flat plane, which is why the sun and planets all follow the same path across the stars in the celestial sphere. This path is called the ecliptic, and the zodiac is a roughly 8-degree wide band of sky around the ecliptic.
Along with the planets and asteroids orbiting the sun is a band of dust left over from the formation of the solar system. This dust band is illuminated by the sun, and long after the sun has set the dust band is visible in dark night skies as a bright glow, radiating away from the sun along the line of the ecliptic. This is the Zodiacal Light, and it is clearly visible on the left side of this image behind Caldron Peak.
To clear skies in wild places!