The year is going to go out with a big bang and a blue moon. What exactly is a blue moon? The second full moon in a calendar month is called a blue moon. Not only will there be a blue moon on New Year’s Eve but there will also be a partial eclipse of this blue moon. Unfortunately, the eclipse will only be visible from Europe, Asia and Africa. The Americas and Australia are out of luck.

A little background on the science and the mythology of blue moons from NASA:

Most months have only one full Moon. The 29.5-day cadence of the lunar cycle matches up almost perfectly with the 28- to 31-day length of calendar months. Indeed, the word “month” comes from “Moon.” Occasionally, however, the one-to-one correspondence breaks down when two full Moons squeeze into a single month. Dec. 2009 is such a month. The first full Moon appeared on Dec. 2nd; the second, a “Blue Moon,” will come on Dec. 31st.

If you told a person in Shakespeare’s day that something happens “once in a Blue Moon” they would attach no astronomical meaning to the statement. Blue moon simply meant rare or absurd, like making a date for the Twelfth of Never. “But meaning is a slippery substance,” says Hiscock. “The phrase ‘Blue Moon’ has been around for more than 400 years, and during that time its meaning has shifted.”

The modern definition sprang up in the 1940s. In those days, the Farmer’s Almanac of Maine offered a definition of Blue Moon so convoluted that even professional astronomers struggled to understand it. It involved factors such as the ecclesiastical dates of Easter and Lent, and the timing of seasons according to the dynamical mean sun. Aiming to explain blue moons to the layman, Sky & Telescope published an article in 1946 entitled “Once in a Blue Moon.” The author James Hugh Pruett cited the 1937 Maine almanac and opined that the “second [full moon] in a month, so I interpret it, is called Blue Moon.”

That was not correct, but at least it could be understood. And thus the modern Blue Moon was born.

Blue moon has other connotations, too. In music, it’s often a symbol of melancholy. According to one Elvis tune, it means “without a love of my own.” On the bright side, he croons in another song, a simple kiss can turn a Blue Moon pure gold.

The modern astronomical Blue Moon occurs in some month every 2.5 years, on average. A Blue Moon falling precisely on Dec. 31st, however, is much more unusual. The last time it happened was in 1990, and the next time won’t be until 2028.

Then there is the song from the early 60’s, entitled, Blue Moon:

Many artists performed this song but most people know the Marcels version best.

If you need a party theme for tomorrow night, go to for all the Blue Moon details.

6 Thoughts to “Blue Moon Eclipse 12/31/09”

  1. mj

    Don’t forget the tasty brew – Blue Moon Beer to go along with your safe New Years Eve theme party!!!!!

  2. Totally great website, mj. Thanks!

  3. Emma

    Then there’s Tony Soprano, “born under a bad sign with a blue moon in your eye.”

  4. Firedancer

    MH, just checking to see if you posted something about our special moon! You didn’t let me down!! 🙂

  5. Francis Torres

    My daughter and I were born during that blue moon,and my daughter was the first hispanic that was born on 1/1/10,I am bleesed with that moon.

  6. Welcome Francis. Good luck to you and your new little one.

    Both of my children were born on full moon but I never checked to see if it was a blue full moon. (otherwise occupied0

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