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?
The saying âonce in a blueÂ moonâ refers to something thatâs exceedingly rare. But in Los Angeles youâll have two chances to see this lunar occurrence Friday, when a so-called blueÂ moon comes into view.
The first opportunity will be Friday morning â yes, the morning â as the blueÂ moon is setting for the day, said Anthony Cook, astronomical observer at Griffith Observatory. Look for the early-morning blueÂ moon between 6:30 and 7 a.m. PDT, he said.
Later in the day, youâll get a second chance to see the blueÂ moon, when it rises at 7:13 p.m. PDT.
So what is a blueÂ moon? Itâs the second full moon within one calendar month.
The moon isnât 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.
âThereâs nothing unusual really about the moon itself,â Cook said. âIt will look like the usual moon.â
The genesis of the term âblueÂ moonâ is unclear.
âItâs not really certainâ where it came from, Cook said. âWhy âblueâ was chosen isnât really known for sure.â
There are, on some occasions, atmospheric conditions that could produce a blue-looking moon, he said. And itâs believed that such conditions sometimes took place at the same time as the second full moon, perhaps leading to the moniker.
A blueÂ moon occurs because the average lunar cycle is 28 to 29 days long. Thatâs why most months see just a single full moon.
The average month, however, is about 30 days long. âAs a result, the lunar cycle gets out of phase with the calendar,â Cook said. âIf you have a full moon right at the beginning of the month, you can get one at the end of the month.â
The last time a blueÂ moon occurred was December 2009. âThe next time will be on July 31, 2015,â Cook said.
He added that there is another definition of âblueÂ moon,â one that comes from the Farmerâs Almanac. When four full moons occur during the course of a single season, the third of those is referred to as the blueÂ moon, Cook said.
âThat kind of full moon is just as rare as a second full moon in a month,â Cook said. âIt also occurs every two or roughly three years.â The next seasonal blueÂ moon will occur in August 2013.
ÂŠ2012 Los Angeles Times