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пятница, 11 мая 2018 г.

When is the next Blue Moon?

 



Most Blue Moons are not blue in color. This photo of a moon among fast-moving clouds was created using special filters. Image via EarthSky Facebook friend Jv Noriega.


Most Blue Moons are not blue in color. This photo of a moon among fast-moving clouds was created using special filters. Image via EarthSky Facebook friend Jv Noriega.





In recent years, people have been using the name Blue Moon for the second of two full moons in a single calendar month. An older definition says a Blue Moon is the third of four full moons in a single season. Someday, you might see an actual blue-colored moon. The term once in a blue moon used to mean something rare. Now that the rules for naming Blue Moons include several different possibilities, Blue Moons are pretty common! The next Blue Moon (second full moon in one calendar month) will be one year from today – January 31, 2018. Follow the links below to learn more about Blue Moons:


Last seasonal Blue Moon on May 21, 2016.


Next monthly Blue Moon on January 31, 2018.


Which Blue Moon definition is better?


Can a moon be blue in color?


Can there be two Blue Moons in a single calendar year?




Desert Blue Moon from our friend Priya Kumar in Oman. August, 2012. Thank you, Priya!



Blue Moon as third full moon of four in a season. The Maine Farmer’s Almanac defined a Blue Moon as an extra full moon that occurred in a season. One season – winter, spring, fall, summer – typically has three full moons. If a season has four full moons, then the third full moon may be called a Blue Moon.


There was a Blue Moon by this definition happened on November 21, 2010. Another occurred on August 20-21, 2013.


It last happened on May 21, 2016.


The next seasonal Blue Moon (third of four full moons in one season) will take place on May 18, 2019.




This photo was created using special blue filters, too. Image via EarthSky Facebook friend Jv Noriega.



Next monthly Blue Moon on January 31, 2018. In recent decades, many people have begun using the name Blue Moon to describe the second full moon of a calendar month. There was a full moon on July 2, 2015. There was another full moon on July 31, 2015. So the July 31, 2015, full moon was called a Blue Moon, according to this definition.


The next one will be on January 31, 2018.


The time between one full moon and the next is close to the length of a calendar month. So the only time one month can have two full moons is when the first full moon happens in the first few days of the month. This happens every 2-3 years, so these sorts of Blue Moons come about that often.


The idea of a Blue Moon as the second full moon in a month stemmed from the March 1946 issue of Sky and Telescope magazine, which contained an article called “Once in a Blue Moon” by James Hugh Pruett. Pruett was referring to the 1937 Maine Farmer’s Almanac, but he inadvertently simplified the definition. He wrote:


Seven times in 19 years there were — and still are — 13 full moons in a year. This gives 11 months with one full moon each and one with two. This second in a month, so I interpret it, was called Blue Moon.


Had James Hugh Pruett looked at the actual date of the 1937 Blue Moon, he would have found that it had occurred on August 21, 1937. Also, there were only 12 full moons in 1937. You need 13 full moons in one calendar year to have two full moons in one calendar month.


However, that fortuitous oversight gave birth to a new and perfectly understandable definition for Blue Moon.


EarthSky’s Deborah Byrd happened upon a copy of this old 1946 issue of Sky and Telescope in the stacks of the Peridier Library at the University of Texas Astronomy Department in the late 1970s. Afterward, she began using the term Blue Moon to describe the second full moon in a calendar month on the radio. Later, this definition of Blue Moon was also popularized by a book for children by Margot McLoon-Basta and Alice Sigel, called “Kids’ World Almanac of Records and Facts,” published in New York by World Almanac Publications, in 1985. The second-full-moon-in-a-month definition was also used in the board game Trivial Pursuit.


Today, it has become part of folklore.




What most call a Blue Moon isn’t blue in color. It’s only Blue in name. This great moon photo from EarthSky Facebook friend Rebecca Lacey in Cambridge, Idaho.



 


Source earthsky


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