β Monocerotis
February 2011 :
It’s an annual ritual. Go outside on a crisp, clear February evening. Aim telescope towards a misty patch of light in Orion’s Sword. Gaze in awe and wonder at M42 – the Orion Nebula. I suggest that, after your pilgrimage to the Orion Nebula this year, you travel 12 degrees eastward into the obscure constellation Monoceros. There, you’ll find the finest triple star in the night sky – beta (?) Monocerotis.
Described by its discoverer William Herschel (1781) as “one of the most beautiful sights in the heavens,” beta Mon is a dazzling trio of pure-white stars. What separates beta Mon from most triple stars is the closeness of its components and their similarity in brightness.
Viewed with low power, beta Mon an attractive double star whose magnitude 4.6 and 5.0 components are separated by 7 arc-seconds. Ramp up the magnification (100X with an ordinary 60mm refractor will do the job), and you’ll see the third star (magnitude 5.3) a mere 3 arc-seconds from the 5.0 magnitude component. The three form a curved row 10 arc-seconds across.
I’ve always written that double stars are twice the fun. As for triple stars – well, you get the idea! Triple your observing fun with a visit to beta Monocerotis.
Your comments on this column are welcome. E-mail me at gchaple@hotmail.com.
