Blue Moon

What`s a 'Blue Moon'?

Comrade Jojo shared a very interesting topic on his blog. He talked about a 'once in a blue moon' event for New Years Eve.

A blue moon is a full moon that is not timed to the regular monthly pattern. Most years have twelve full moons which occur approximately monthly, but in addition to those twelve full lunar cycles, each solar calendar year contains an excess of roughly eleven days compared to the lunar year. The extra days accumulate, so that every two or three years (on average about every 2.7154 years), there is an extra full moon. The extra moon is called a "blue moon."

An article posted by David Brown stated that when something unusual happens, we often hear that it was "once in a Blue Moon." But how rare to experience a "blue moon" on a very special day, New Year's Eve. Tomorrow you can witness that even more unusual event.

There really are "blue moons, but the term has nothing to do with the color of our satellite — it will look just the same as any other full moon.

We call it a "blue moon" when a second full moon appears during a single month. This month the Moon was full on December 2, and will be again on December 31, so that identifies the New Years Eve moon as a blue one. Actually, that definition is fairly recent, dating from a blooper in the pages of Sky & Telescope in 1946. You can read that story here.

Why are the appearances of blue moons unusual events? Most years have twelve full moons, taking place about once every month (the words "month" and "moon" come from the same Old English root). But the period of the moon's orbit around the Earth isn't quite a month long, so at the end of every year there are a few extra days. Those days add up and about every 2.7 years there is an extra full moon to make up the difference.

There are many theories where the term came from. One relates to the fact that in Medieval times the English clergy used the phases of the moon to determine the dates for Lent and Easter. If a full moon appeared too early, it was called a "betrayer moon," using the Old English word "belewe," meaning either betrayer or blue. Later English writers confused the two meanings.

Whatever the reasons, what better way to celebrate the end of the year just ending than to step outside and observe the rising full moon. How many more blue moons will come before two such unique events again coincide?
Because of geometry, a full moon always rises in the East opposite the setting sun, so right after dark is a good time to view Luna in her splendor. But if you wait until the traditional Midnight, the moment of the changing of the year, it may be an even more spectacular sight, for then the blue moon will be shining brightly from directly overhead, halfway across the sky.

Tomorrow is the last day of 2009 and it would be romantic to view this blue moon and the last sunset of 2009!^^,