A blue moon is an additional full moon that appears in a subdivision of a year: the third of four full moons in a season.
The phrase in modern usage has nothing to do with the actual color of the Moon, although a visually blue Moon (the Moon appearing with a bluish tinge) may occur under certain atmospheric conditions—for instance, if volcanic eruptions or fires release particles in the atmosphere of just the right size to preferentially scatter red light.
2009Dec, 31
Both a blue moon and a lunar eclipse occur.
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Events on 2009
- 26Jan
2009 Malagasy political crisis
Rioting breaks out in Antananarivo, Madagascar, sparking a political crisis that will result in the replacement of President Marc Ravalomanana with Andry Rajoelina. - 29Jan
Rod Blagojevich corruption charges
Governor of Illinois Rod Blagojevich is removed from office following his conviction of several corruption charges, including the alleged solicitation of personal benefit in exchange for an appointment to the United States Senate as a replacement for then-U.S. president-elect Barack Obama. - 12Jun
2009 Iranian election protests
A disputed presidential election in Iran leads to wide-ranging local and international protests. - 4Jul
September 11 attacks
The Statue of Liberty's crown reopens to the public after eight years of closure due to security concerns following the September 11 attacks. - 5Nov
2009 Fort Hood shooting
U.S. Army Major Nidal Malik Hasan murders 13 and wounds 32 at Fort Hood, Texas in the deadliest mass shooting at a U.S. military installation.