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Changing The Cosmic Calendar

It is quite evident that winter is peeking around the corner. The tell tail signs are, howling north winds, negative temperatures and yes - the flakey white stuff is making its appearance. Long gone are the mosquito ridden, warm humid nights of July and August. We also notice the change of seasons by looking up - way up. With a little practice you can use the constellations as a celestial calendar just the early farmers along the Nile did thousands of years ago. They determined than when the bright star Sirius (alpha Canis Majoris) rose a couple of hours before the Sun, the change of seasons would soon cause the Nile waters to rise, thus wiping out their crops. The harvest was on. Some six months later when Leo the Lion (backwards question mark) would assent in the east, it was pretty well safe to plant the new crops as spring was in the air.

Over the course of our 365.25 day orbit around the sun, our world endures the climatic change of the four seasons. This is a result of Earth's 23.5 degree tilt on its axis. Check out any class room globe. That tilt is not for esthetics purposes but is true to nature. As we dance around the Sun from year to year, Earth's axis is always pointing to the same specific location in space - close to the North Star named Polaris. June 21 st marks the first day of summer in the northern hemisphere with the Sun is at its highest point in the sky, bathing us in its brilliance for about fifteen and a half hours. The North Pole sees the Sun all day long without setting. This is in sharp contrast to the mere eight and a half hours of sunlight on the first day of winter - which this year rings in on December 21 st at 1:35 p.m. eastern time, when our closest star is at its lowest point in the sky. Now the North Polar Region is mid way through its five months of darkness. The lack of sunlight keeps the Pole extremely cold, thus allowing frigid air to pump down, blanketing us in its frosty grip. Like cooking, the longer something stays in the microwave or oven - the hotter it will get. Same goes for the freezer.

Another motion the Earth goes endures on a daily basis is rotation. Traditionally we signify twenty-four hours as one calendar day. Truth to the matter is we spin once every 23 hours, 56 minutes and 04 seconds. This four minutes lull, allows the stars and their patterns to rise a bit earlier each night in the east as the old ones set in the west. In other words a particular star or planet would rise close to a half an hour earlier tonight as it did a week ago. Over the course of the entire year, we come full circle. We cannot include the Moon as it circles us in a mere 29.5 days.

With this said the winter constellations of Taurus the Bull, Orion the Hunter and friends are creeping up in the east during early evening hours. This area including Gemini contains eighteen of the brightest stars in the sky. Orion is by far the easiest pattern to recognize. The distinctive three stars in a row marks the Hunter's belt. Two stars above the belt indicate his shoulders and two more below are his feet. Dropping down half way from the middle belt star to his feet is a hazy patch of light. This is called the Great Nebula in Orion and is the birthplace or stellar nursery of new stars. In this distant shell of gas and dust, young stars are developing. The sibling's radiation is causing the cloud to glow. This creation of cosmic life lies only 1,500 light years from us, keeping in mind that one light year measures close to 10 trillion kilometers or 6 trillion miles.

Print out the enclosed star map or refer to the current sky over Ottawa and try to recognize a few starry patterns including Orion. Before you print from the website , be sure to click the 'black on white' button on the bottom and hit 'submit' to save on toner or ink. You can also advance into the future or gaze at the sky in the past. Just set the values. You can also find the planet Mars to the right of the Pleiades star cluster (the heart of Taurus the Bull). The red planet was closest to Earth at the end of October and our distance is slowly widening a few tens of thousand of kilometers per hour. It will be closest to us every twenty-six months. The ringed planet Saturn will be up before local midnight. Venus beacons low in the western sky for the next few months as seen after sunset. If you have a telescope, train it on this jewel as it undergoes a changing phase structure like the moon.

The next monthly meeting of the Royal Astronomical Society of Canada will take place on Friday December 2 nd at 8:00 p.m. in the main auditorium of the Canada Science and Technology Museum. Admission and parking are free. Before December's meeting the semi annual swap table will take place on stage. Here people can buy and sell astronomical items along with books and magazines.

Bundle up and enjoy the change of season before it gets too cold. Send me your observations and your thoughts of the winter sky.

Clear skies,
Gary Boyle
garyboyle@sympatico.ca

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