The last night of 2009 will be unusual, one that comes only once in a blue moon, literally. Partygoers and sky gazers will be able to see a second full moon this month on December 31 — a phenomenon known as ‘Blue Moon’.

After midnight, as people ring in the New Year, there will also be a partial lunar eclipse, which will be visible from Delhi. Officials say no equipment will be required to watch the partial lunar eclipse. Officials say normally a year has 12 full moons, but the 13th moon is a rare phenomenon. This month’s first full moon was on December 2.

C B Devgan, president of SPACE, which works towards science popularisation, says, “A second moon in one month happens because a full moon occurs every 29-and-a-half days, so there are extra days every year leading to an extra moon every two-three years.” But unlike meteor showers and solar eclipses that generate a lot of interest, no star gazing trips have been heard so far, officials said.

The saying ‘once in a blue moon’, is derived from this phenomenon after the second moon appeared blue from Indonesia due to a volcanic eruption in 1883. The gases from the eruption formed a film in the atmosphere that made the sunset look green and the moon blue. While blue moon occurs every 2 to 3 years, two blue moons in a year happen every 18 to 19 years. The last time India had a blue moon was in June, 2007. The next New Year’s eve full moon will be in 2028. (Indian Express)