Blue moon: Two chances to see this rare event
Blue moon: Early risers will see the blue moon Friday morning and in the evening. What's a blue moon?
A full moon is seen from the Atahualpa Stadium in Quito. This is the second time in this month that a full moon is seen - the first was on August 1 to 2. This phenomenon, which is referred to as the Blue Moon. The next blue moon is in 2015.
REUTERS/Gary Granja
Los Angeles
The saying 鈥渙nce in a blue聽moon鈥� refers to something that鈥檚 exceedingly rare. But in Los Angeles you鈥檒l have two chances to see this lunar occurrence Friday, when a so-called blue聽moon comes into view.
The first opportunity will be Friday morning 鈥� yes, the morning 鈥� as the blue聽moon is setting for the day, said Anthony Cook, astronomical observer at Griffith Observatory. Look for the early-morning blue聽moon between 6:30 and 7 a.m. PDT, he said.
Later in the day, you鈥檒l get a second chance to see the blue聽moon, when it rises at 7:13 p.m. PDT.
So what is a blue聽moon? It鈥檚 the second full moon within one calendar month.
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The moon isn鈥檛 actually blue. And it might even take on an orange hue as it starts to rise in the sky, Cook said. If anything, the Friday night moon will most likely appear an especially brilliant white.
鈥淭here鈥檚 nothing unusual really about the moon itself,鈥� Cook said. 鈥淚t will look like the usual moon.鈥�
The genesis of the term 鈥渂lue聽moon鈥� is unclear.
鈥淚t鈥檚 not really certain鈥� where it came from, Cook said. 鈥淲hy 鈥榖lue鈥� was chosen isn鈥檛 really known for sure.鈥�
There are, on some occasions, atmospheric conditions that could produce a blue-looking moon, he said. And it鈥檚 believed that such conditions sometimes took place at the same time as the second full moon, perhaps leading to the moniker.
A blue聽moon occurs because the average lunar cycle is 28 to 29 days long. That鈥檚 why most months see just a single full moon.
The average month, however, is about 30 days long. 鈥淎s a result, the lunar cycle gets out of phase with the calendar,鈥� Cook said. 鈥淚f you have a full moon right at the beginning of the month, you can get one at the end of the month.鈥�
The last time a blue聽moon occurred was December 2009. 鈥淭he next time will be on July 31, 2015,鈥� Cook said.
He added that there is another definition of 鈥渂lue聽moon,鈥� one that comes from the Farmer鈥檚 Almanac. When four full moons occur during the course of a single season, the third of those is referred to as the blue聽moon, Cook said.
鈥淭hat kind of full moon is just as rare as a second full moon in a month,鈥� Cook said. 鈥淚t also occurs every two or roughly three years.鈥� The next seasonal blue聽moon will occur in August 2013.
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