BLUE MOON OF NEW YEARS EVE 2010

Once in a blue moon there is one on New Year's Eve. Revelers ringing in 2010 will be treated to a so-called blue moon. According to popular definition, a blue moon is the second full moon in a month. But don't expect it to be blue — the name has nothing to do with the color of our closest celestial neighbor. A full moon occurred on Dec. 2. It will appear again on Thursday in time for the New Year's countdown. The New Year's Eve blue moon will be visible in the United States, Canada, Europe, South America and Africa. For partygoers in Australia and Asia, the full moon does not show up until New Year's Day, making January a blue moon month for them. However, the Eastern Hemisphere can celebrate with a partial lunar eclipse on New Year's Eve when part of the moon enters the Earth's shadow. The eclipse will not be visible in the Americas.

A full moon occurs every 29.5 days, and most years have 12. (There are 12 full moons most years but every two or three years there's an extra full moon which is called a 'Blue Moon'). On average, an extra full moon in a month — a blue moon — occurs every 2.5 years. The last time there was a lunar double take was in May 2007. New Year's Eve blue moons are rarer, occurring every 19 years. The last time was in 1990; the next one won't come again until 2028.

Blue moons have no astronomical significance. 'Blue moon' is just a name in the same sense as a `hunter's moon' or a `harvest moon'. The popular definition of blue moon came about after a writer for Sky & Telescope magazine in 1946 misinterpreted the Maine Farmer's Almanac and labeled a blue moon as the second full moon in a month. In fact, the almanac defined a blue moon as the third full moon in a season with four full moon, not the usual three.

Though Sky dan Telescope corrected the error decades later, the definition caught on. For purists, however, this New Year's Eve full moon doesn't even qualify as a blue moon. It's just the first full moon of the winter season.

The most literal meaning of Blue Moon is when a casual observer regards it as unusually bluish. This effect can be triggered by smoke or dust particles in the atmosphere, as happened after forest fires in Sweden and Canada in 1950. In 1883, the Krakatoa volcanic eruption in Java left the moon looking blue for nearly two years.

Image Sources: http://www.phys.ncku.edu.tw/~astrolab/mirrors/apod_e/image/0407/bluemoon_icstars_big.jpg