First of all, I admit that Cygnus has just about everything: It’s a northern star group that’s well placed for Canadian skywatchers; it features bright stars that form a famous asterism (the Northern Cross); and it enjoys a spectacular location in the band of the Milky Way. What’s more, throughout September, Cygnus flies almost directly overhead soon after nightfall. The usual neighbourhood annoyances — houses, trees and streetlights — won’t obscure your late-summer view of the soaring swan.
Visualizing the Nothern Cross makes it easier to identify the constellation’s leading lights. First-magnitude Deneb, which marks the top of the cross, is the tail of the swan.
At the other end of the cross, third-magnitude Albirio locates the swan’s head. Three bright stars that form the crossbar suggest the bird’s outstretched wings in full flight. For the keen-eyed, a dozen fainter stars (not plotted on the chart at right) outline the wings completely. Gazing up at a dark, clear sky, you can imagine Cygnus gliding southward among the star clouds of the Milky Way.
And that brings me to the ubiquitous Canada goose (Branta canadensis). Huge numbers of Canada geese embark on their annual migration at this time of year. The V-shaped flocks are as much a Canadian symbol as are the beaver and the maple leaf. They are also a sign of the changing seasons. As the lengthening September nights turn chilly, I like to gaze up at Cygnus and picture it not as a swan but as a cackling B. canadensis heading south for the winter. For me, it’s the quintessential Canadian constellation. I even have a name for it: Branta Borealis, the northern goose.
This homespun star lore had its genesis 10 years ago, when my wife and I lived near a provincial park in British Columbia’s southern Okanagan Valley. Located well away from city lights, our hillside acreage offered a dark and tranquil setting for astronomy. During two back-to-back observing sessions in late September 1993, a rare blend of sight and sound brought my Branta Borealis to life.
A 4 a.m. alarm triggered the first session. Fuzzy-brained and bleary-eyed, I stumbled outside to my backyard observing site. The night was cool, clear and perfectly still. The waxing gibbous Moon had set moments earlier, and dawn was a good 90 minutes away. The winter constellations — a harbinger of frosty nights to come — blazed in the coal-black eastern sky. Needless to say, my mental fuzziness quickly disappeared. Eager for a peek at some favourite winter wonders, I swung my 17.5-inch Dobsonian telescope into action.
Long minutes passed with my eye glued to the eyepiece. Then, at about 4:30 a.m., I heard a distant racket far above me. It was a huge formation of Canada geese flying south. Although I couldn’t see the birds, I could hear them honking along the Milky Way. It was evidence as sure as anything astronomical that the seasons were changing.
At that hour, Cygnus was diving into the northwestern horizon. The high-flying flock was slowly heading the other way. I first heard the birds coursing through Perseus near the zenith. Perhaps my imagination got the better of me, but it seemed as though their collective cackle was emanating from the Milky Way itself. The geese advanced to Auriga, flew under the feet of Gemini, drifted by Orion and finally descended past brilliant Sirius to the southeast horizon. Standing perfectly still, I was able to hear the last few stragglers fading into the distance.
There were more geese the next evening at dusk. The cacophony was louder this time, and after a moment, I spotted them by moonlight. The formation again sailed overhead but closer and, this time, right through Cygnus. The lead goose pushed ahead with at least 20 others in tow. That’s when I dreamed up their cosmic counterpart, Branta Borealis, to guide them along as they winged their way southward under the stars.
The month of September delivers the last best-quality summer nights of the year. If you find yourself under a cool, clear sky at nightfall, be sure to take a gander at Cygnus. You never know what you might see — or hear.