Sirius
April 2010 :
An unwritten law in astronomy states that you should avoid observing any sky object when it’s near the horizon. First of all, incoming light has to pass through a greater amount of earth’s atmosphere when approaching from a low altitude. Secondly, ripples from escaping ground heat create turbulence that’s most troublesome near the horizon.
However, if you want to experience one of the night sky’s loveliest treats, ignore that law and look at Sirius when it’s low in the sky. When the night sky’s brightest star is situated high above the southern horizon as it is after sunset on February and March evenings, it’s a magnificent sight. A gleaming, sparkling diamond, Sirius captivates the beholder, no matter whether viewed with unaided eye, binocular, or telescope.
Sirius is now on the wane, setting soon after sunset. As it nears the horizon, something magical happens. That same atmospheric turbulence that wreaks havoc on sky objects refracts the light from Sirius, causing it to sparkle in a dazzling array of gemlike hues. Its diamond like radiance is interrupted by flashes of ruby red and emerald green - a visually entrancing sight.
Next time you set out to do some “serious” astronomy, try a moment to make a “Sirius” observation. You’ll be delighted you did.
Your comments on this column are welcome. E-mail me at gchaple@hotmail.com.
