There will be two full moons in July and the second one will be a so-called blue moon, the first time that there have been two full moons in one month since 2012. The term “blue” does not refer to the color of the second moon, but to the rarity of having one month with two full moons in it. The term comes from the March 1946 issue of Sky and Telescope magazine, which contained an article by James Hugh Pruett called Once in a Blue Moon.
Full moons generally occur roughly once during an entire calendar month, every 29.5 days. For two of them to happen in one month, the first one needs to be within the first couple days or so of the month. The phrase “Once in a Blue Moon,” which causes some people to think of something that only happens in fairy tales, has come to mean something that happens, but rarely, like having one month with two full moons in it.
According to the site Astronomy Calendar and the Origins of Full Moon Names, originally when the term “Blue Moon” was coined, it did not refer to the second full moon of a month. It referred to a season, or quarter of a year, that had four instead of the usual three full moons in it. “Blue” was a corruption of the archaic word “belewe,” meaning “traitor.”
The two full moons in the month of July will occur on Thursday, July 2 and on July 31, the last day of the month. The first full moon of July has several names that has been given to it from folklore and Native American traditions, like the “Thunder Moon,” “Hay Moon” and the “Buck Moon.”
The term “Thunder Moon” comes from there often being thunderstorms in early July in parts of the United States. The first full moon is sometimes called the “Buck Moon,” because buck deer begin to grow their antlers around this time of the summer.
It rises at sunset and sets at sunrise, making it the only full moon of July that spends all of its time in the night sky. The second one, the “Blue Moon,” will spend some of its time being visible in the day sky. Years that have 13 full moons in them are called “Blue Moon Years.”
There can be nights when the moon looks as if it is blue, but that is because of certain atmospheric conditions, not because the moon has actually turned blue. These types of conditions can happen due to volcanic eruptions or a specific type of forest fire, and only people who live nearby such occurrences are able to see the moon as looking bluish in color.
July’s two full moons with the second one being called a “Blue Moon,” is a rare occurrence that only happens every two to three years or so. The next year that will have a “Blue Moon” in it will not be until 2018. Oddly enough, under the right sorts of conditions, clouds and even the sun can appear to be blue-colored. However, the term “Blue Moon” does not refer to the actual color of the second full moon, but its relative rarity, with the last time a month having two full months in it having occurred in 2012.
Written and Edited By Douglas Cobb
NYC Today: TWO FULL MOONS IN JULY
International business Times UK: Once in a blue moon: July set for
first month with two full moons since 2012
Space.com: Best Night Sky Events of July 2015 (Stargazing Maps)
Times Gazette: Rare Blue Moon Spectacle Unfurls Today And July 31st
Astronomy Calendar and the Origins of Full Moon Names
Photo Courtesy of @sage_solar’s Flickr Page – Creative Commons 2.0