Blue Moon

A blue moon will grace the night sky tonight (Aug. 31), giving skywatchers their last chance to observe this celestial phenomenon for nearly three years. The moon will wax to its full phase at 9:58 a.m. EDT (1358 GMT) today, bringing August's full moon count to two (the first one occurred Aug. 1). Two full moons won't rise in a single month again until July 2015.

The pictures included in today's posting were taken last night -- so the moon was not quite full yet.

The term has long been used to describe rare or absurd happenings.  This somewhat obscure and complicated definition, in fact, is found in the 1937 edition of the "Maine Farmers' Almanac." But in 1946, a writer for "Sky and Telescope" magazine misinterpreted it, declaring a blue moon to be the second full moon in a month with two of them. Widespread adoption of the new (and incorrect) definition apparently began in 1980, after the popular radio program "StarDate" used it during a show.

A Blue Moon occurs because lunar months are not synched up perfectly with our calendar months. It takes the moon 29.5 days to orbit Earth, during which time we see the satellite go through all of its phases. But every calendar month (except February) has 30 or 31 days, so two full moons occasionally get squeezed into a single month.

Though the phrase "once in a blue moon" suggests the phenomenon is exceedingly rare, that's not quite the case. On average, blue moons come around once every 2.7 years, making them more common than the Summer Olympics, or a presidential election in the United States. Some years even boast two blue moons. This last happened in 1999, and it will occur again in 2018.

 

Here are some cool moon photos from the Internet: