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A blue moon to herald in the New Year

A blue moon photographed in October 2003.
A blue moon photographed in October 2003.
By Tom King of Watauga, Texas

Look up in the sky on New Year's Eve and you'll see something other than fireworks. For a rare blue moon marks the close of the first decade of the 21st century.

Whether this rare occurrence is a good luck omen or a foretelling of cataclysm has been a matter of speculation and superstition since man first began to study the heavens.

In modern times, the phrase "once in a blue moon" refers to something that doesn't occur very often. But the phrase also has astronomical significance as it explains the lunar phenomenon of two full moons appearing in the same calendar month.  

Since the time between full moon cycles is roughly 29.5 days, it is not entirely uncommon to have two full moons appearing in the same month, and many years have a least one blue moon.

What is rare however, is that of the moon itself, actually appearing blue.

The blue color of the moon, as shown in the 2003 photograph, was attributed to tiny droplets of water in the air.  According to the NASA website, when water droplets are about 1 micron (one millionth of a meter) in diameter, they strongly scatter red and green light while allowing other colors to pass. A white moonbeam passing through such a misty cloud turns blue.

Clouds of ice crystals, volcanic ash, and smoke from forest fires can also create the appearance of a blue moon, provided the particles are about 1 micron in size.

And with the Mayon Volcano in the Philippines spouting ash and smoke into the night sky, the question of how blue the blue moon will be, remains to be seen.

Additional Information: Some of the best sky watching occurs in parks and forests as the night sky is not as impacted by light pollution usually associated with cities. Click here for a list of parks in/near Anchorage.