Kananaskis in December
My buddy Alex and I head to one our favorite back country ski haunts in Kananaskis Country for some early-season turns. Mid-December skiing in the Canadian Rockies is usually very thin and rocky, but by combining persistence, luck and some local knowledge good skiing can often be found.
The first challenge is crossing a big creek at the beginning of the trail. The weather has been warm, but 24 hours ago a cold front came through and the creek is freezing up, creating an ice dam with a slushy pond behind it. Being the tenacious type, Alex is determined to cross, so we run back to the car for rubber boots. One pair of rubber boots… Expecting a quick, wet plunge that will end our day early, I hang out on the shore snapping shots while Alex carefully wanders out and probes his way across the newly formed ice dam. The good news is that he doesn’t fall in, but the ice is too soft and we can’t cross here. We decide to work our way upstream for quite a ways before finding a suitable place to cross.
The snow down low in the valley is very thin, but the higher we go the better it gets, and by the time we get up into the alpine the snowpack is quite solid, with a decent layer of wind-blown soft snow on top.
It’s very late in the afternoon by the time we turn around and start the ski descent. The advantage of this late descent is that we get to enjoy the beautiful alpenglow on the surrounding peaks from up high, but the disadvantage, of course, is that we will be skiing back to the car in the dark. Well worth it!
The sky has been beautifully clear all day, and after dinner in Canmore I decide to head back to the mountains to do some night photography. The Universe is really just an (infinite) extension of the great outdoors, and with 16 hours of darkness this time of year it’s a great season to do some star gazing.
Orion the hunter
By the time I drive south from Canmore back into Kananaskis the constellation of Orion has risen above the horizon. Orion is one of the most easily recognized and famous constellations in the sky, and is full of fascinating deep space objects.
In Western culture, Orion, like many of the constellations, was named after a figure in Greek mythology. Orion the Hunter first appeared in Homer’s epic Odyssey. Humans have been imagining stellar constellations long before the ancient Greeks, and archaeologists have speculated that the constellation of Orion was carved into mammoth ivory by prehistoric humans 32,000 years ago!
Giant stars of Orion
Orion is such a spectacular constellation because its main stars are so bright, and because it actually looks like something. And its stars do not appear bright just because they are close to us, but because they are also much more luminous than our Sun, putting out many 1000s of times the energy.
Generally, the more massive a star is, the hotter it is, the more quickly it burns through its supply of hydrogen fuel, and the shorter its life. Just like a the white-hot filament in an old-fashioned tungsten light bulb, colour of a star is determined by its surface temperature. The relationship between a star’s mass, lifetime, luminosity and surface temperature (colour) was first characterized around 1910 and summarized in the Hertzsprung-Russell diagram. The relationship between a stars luminosity and temperature, as revealed by this diagram, drove the understanding of stellar evolution physics.
The brightest star in Orion is Rigel, a young, blue super-giant star, only 10 million years old and 772 light-years away. It appears very blue/white to the naked eye, weights in at 17 times the mass of our Sun and emits 85,000x as much light.
In contrast, Betelgeuse appears very red to the naked eye, and is classified as a red super-giant star. It is a variable star, with its luminosity varying between 90,000 and 150,000x our sun. It is also one of the largest known stars, and would easily engulf both Earth and Mars, reaching roughly out to the orbit of Jupiter if it replaced our Sun. It is also very young, less than 10 million years, but is consuming its fuel very quickly and will explode as a supernova in the (relatively) near future, likely within one million years. Not to worry, however, because at around 650 light-years away we should be safe from being cooked when this giant explodes.
The three brilliant stars of Orion’s Belt, Alnitak, Alnilam and Mintaka, are all giant, young blue stars, with luminosities between 90,000x and 375,000x our Sun’s output.
M42, the great nebula in Orion
Stars are created from the gravitational collapse of vast clouds of gas and dust. As these clouds collapse, the gas density increases until the pressure and temperature are enough to initiate nuclear fusion, and new stars are born. The young stars start pumping out electro-magnetic radiation and particles (solar wind), eroding the surrounding gas clouds. This tug-of-war between gravity and radiation shapes the gas clouds, with the young stars carving out bubbles of relatively empty space and illuminating the clouds from within. The results are stunning nebulas, and the closest one to Earth is known as Messier 42, the Great Orion Nebula.
This nebula is so large and close to Earth that it is visible to the naked eye, appearing as the blurry middle “star” in Orion’s sword. The image at left was made with a 50mm camera lens, which is not much of a telescope!
Because M42 is the closest star-forming region to Earth, it is one of the most photographed and studied by both amateur and professional astronomers. Numerous discoveries have been made in this region, including the first image of solar-system formation around a new-born star.
Taurus the bull
Taurus is easily recognizable by the distinct V-shaped group of stars called the Hyades cluster, which is actually the nearest star cluster to Earth. The brightest star in Taurus, Aldebaran, is actually not a member of the Hyades cluster and is much closer to Earth than the cluster stars. Another truly giant star, Aldebaran is 44x the diameter of our sun and puts out 425x as much energy. A picture really puts this into perspective.
M1, the Crab nebula
Just above the lower-left star in Taurus is a small fuzzy spot with an incredible history. In July of 1054 an extremely bright star suddenly appeared in the sky. Chinese astronomers of the Song Dynasty noted the appearance of this “guest star”, which was so bright that it was visible in daylight for 23 days and visible in the night sky for almost two years. The most detailed record from Japan describes a guest star that was as big as Jupiter, and accounts from Iraq talk of a spectacular new star in that year.
As seen at left, the Crab Nebula is visible through a puny 50mm lens, but is certainly not much of a sight. The stunning Hubble image below really reveals what happened here: the “guest star” was actually the explosive death of a star, now known as Supernova 1054.
The remnants of this incredibly powerful explosion are still expanding, at roughly 1500 kilometres per second (0.5% of lightspeed), and in the nearly 1000 years since the exposion have grown to about 11 light-years in diameter. That fuzzy little spot in the sky is really big: 11 light-years is about 100,000 billion kilometres. The visible expansion of the nebula was first noticed in the early 1900s, and by back-tracking this expansion the age of the nebula was estimated to be about 900 years.
At its centre is a neutron star called the Crab Pulsar, only 28-30km in diameter and spinning at an incredible 30 revolutions per second. This means that the surface of this star is moving at around 2700 km/s, or nearly 1% of light speed! This neutron star is the strongest persistent source of X-ray and gamma ray energy in the sky.
In 1758, the French astronomer Charles Messier was watching for the return of Halley’s Comet when he observed a fuzzy patch in the constellation Taurus. After noting that the object did not move or change brightness over several nights, Messier concluded that this was not a comet, and thereby started his famous catalog of non-comets that eventually grew to include over 100 of the most interesting deep-space objects.
“What caused me to undertake the catalog was the nebula I discovered above the southern horn of Taurus on September 12, 1758, while observing the comet of that year. … This nebula had such a resemblance to a comet in its form and brightness that I endeavored to find others, so that astronomers would not confuse these same nebulae with comets just beginning to shine.” -Charles Messier
M45, Pleiades cluster
Further south from Taurus and easily visible to the naked eyes is the famous Pleiades cluster, the Seven Sisters, consisting of seven hot, young blue stars.
Being easily visible to the naked eye, this cluster has been known since antiquity to cultures all around the world, with the first likely depiction on a bronze disk from the 16th century BC.
Seven stars are visible to the naked eye, but the cluster contains many than that, with Galileo Galilei counting 36 stars when he first viewed the cluster through his telescope in 1610 and modern analysis showing over 1000 stars.
M36, M37 and M38 star clusters
Connected to Taurus and sharing the star Alnath is the constellation of Auriga. Looking towards Alnath you are looking through the plane of the Milky Way, but exactly opposite it’s centre. The big deal of looking through the plane of the Milky Way is that’s where all the stars and most of the interesting objects are.
Stars are created when massive gas clouds collapse, and these clouds are big enough to form dozens or hundreds of stars at a time. As the stars ignite and start to emit radiation the gas clouds are blown away, revealing the stars (and their planets) in mostly empty space. These clusters of stars are loosely bound to each other by gravity, and tend to stay more-or-less together for 100s of millions of years.
In the constellation Auriga are several star clusters of varying ages. Through binoculars or a small lens they appear as small clumps of stars against a background already dense with stars.
Messier 36 is a small, young cluster about 3600 light years away 25 million years old containing approximately 60 stars in a ball about 14 light-years across.
Messier 37 is much older, around 500 million years, and farther away, about 4500 light-years. With an estimated 2000 stars in a diameter of about 30 light years it is much bigger and denser than M36.
Roughly half way between M36 and M37, in both age and size, sits M38. Compare it’s estimated age, 220 million years, to the approximate age of our Sun, 4.6 billion years, so see how relatively young these star clusters are.
The big picture
I’ve only described a few of the many deep-sky objects in this part of the sky. Click in the image below to zoom in and explore this familiar and fascinating part of the universe.
Click to zoom into the high-resolution image.
This high-resolution image was stitched together from eight 3-minute exposures, taken with a 50mm lens at ISO 1600. Because the photography site, on the Smith-Dorrian road in Kananaskis, is only 80km from the city of Calgary, there is significant light pollution visible in these long exposures. I use a CLS light-pollution filter from Astronomik to help remove the resulting sky-glow and improve image contrast.
A different perspective
Of course, the stars that make up Orion are scattered all across 3D space, with the closest star 240 light-years away and the furthest 1300 light-years. This results in the constellation completely losing it’s familiar shape when viewed from a different perspective, which is beautifully shown in this illustration by artist and scientist Mark Garlick.
The universe is vast beyond imagination and full of wonders and insight into who, what and where we really are. Worth exploring!
– Darren Foltinek, 2014