The Backyard Astronomer: Orion the Hunter, birthplace of stars, stalks the winter sky
For obvious reasons, winter in Canada does not entice people to venture outdoors and stargaze. But although the nights can be long and cold, they can also be things of beauty.
Your reward for braving the frosty still of the night can be seeing the most iconic constellation of the entire sky. The seven bright suns that form Orion the Hunter are part of a larger picture of a dozen bright winter stars belonging to other nearby constellations.
You can always look through your windows, from the warmth of your comfy home, but to experience the true wintry celestial landscape, you need bundle up and travel to a dark site away from stray light sources on a moonless night. Here, the ghostly silence of the night allows one to hear one's own heartbeat.
Along with seeing the imaginary Taurus the Bull constellation (in the upper right of the night-sky chart at the bottom of this article) battling Orion (in the lower centre), look at the beautiful Pleiades star cluster (upper right), the heart of the angry bull. Also referred to as the Seven Sisters, the Pleiades reside about 450 light-years from us. (To get an idea of how far away that actually is, consider that the speed of light is approximately 300,000 kilometres per second.)
To the upper left of Orion are the twins of the Gemini constellation, consisting of the bright stars called Pollux (yellowish) and Castor (blue), located 33 and 51 light-years, respectively, from Earth. Use binoculars to locate a beautiful open star cluster, catalogued as M35, near Castor's right foot. The cluster, appearing about the size of the full moon, contains a couple of hundred stars and is some 2,800 light-years away.
Above the twins (top, centre) is the constellation Auriga the Charioteer. The bright star is named Capella and resides 42 light-years away.
There are also three open star clusters located in the southern part of the constellation. Appearing in a somewhat curved line from (bottom) left to right on the chart, they bear the catalogue numbers M37, M36 and M38.
They are all in the 4,200 to 4,500 light-year range from us, meaning that the starlight from these clusters that we see now left its source around the time the Great Pyramids in Egypt were built.
(Now you know why some astronomers describe telescopes as time machines, because objects observed through them—as well as with the naked eye—show them as they were at the time they produced the light we see now, after having travelled all that distance to our eyes. In other words, if a star 5,000 light-years away were to suddenly [to our eyes] go supernova and cease to exist as a star, that event would actually have taken place 5,000 years ago.)
The winter sky is also where we find the fainter and less dense edge of our Milky Way galaxy, on the left side of Orion. Dark skies are required to see this winter portion of our galaxy (as opposed to the heavy concentration of hundreds of millions of distant stars in the centre of the galaxy easily seen in the constellation Sagittarias in the southern hemisphere's night sky from June to October).
Back to Orion the Hunter, which is outlined by two stars for his "shoulders", two for his "feet", and three in a row for his famous "belt". From the belt, look for the imaginary sword hanging down with a fuzzy-looking object in it (in the centre of the triangle between the feet and the belt). This is an "emission nebula"—the Great Orion Nebula, or M42—a cloud of heated, ionized gases emitting radiation that causes it to glow.
This stellar nursery is slowly collapsing and condensing pockets of gas and dust in the nebula to eventually form a couple thousand stars. The belt stars, from left to right, are named Alnitak (817 light-years away), Alnilam (1,976 light-years) and Mintaka (916 light-years), while the nebula itself is about 1,500 light-years away.
Embrace the night sky for all it has to offer, no matter what time of year.
Till next time, clear skies.