The full moon of May is already upon us. Known as the “Flower Moon,” this month’s full moon is particularly special because it also doubles as a blue moon; and a rare one at that.
As passionate sky watchers are very well aware, the term of “blue moon” refers to the second full moon occurring in a calendar month. Also known as a calendrical “blue moon,” the phenomenon can be seen in such occasions where two full moons rise within the same month, typically on the first day and the last day of the month.
Since it takes the moon about 29.5 days to complete one cycle of phases, from new moon to new moon, “if a full Moon occurs on the first of a month, there will be a second full Moon at the end of the month, too,” explains The Old Farmer’s Almanac. Evidently, the month of February is exempt from this rule, given that it has fewer days than the rest of the calendar months.
While this is the most well-known definition of a “blue moon,” this is not the case for the May full moon. The “Flower Moon” of May 18 actually exemplifies a different type of “blue moon,” one that occurs once a season.
Dubbed a seasonal “blue moon,” this phenomenon can be observed during astronomical seasons that boast four full moons and refers to the third full moon that rises during the season.
“There are four full moons in spring 2019: March 20, April 19, May 18, and June 17. That makes this month’s full moon the ‘blue moon,'” notes Space.
According to AccuWeather, this type of full moon only comes along once every two to three years. After tonight, stargazers will have to wait a little over two years for the next opportunity to see a seasonal “blue moon.”
The following seasonal “blue moon” rises on August 22, 2021. This means that tonight’s celestial event will showcase the last “blue moon” of the decade.
While the shining orb may have earned the moniker of “blue moon,” the full moon of May won’t actually light up the sky in mysterious shades of blue, remarks Space.
“Of course, the moon itself will retain the bright white appearance it usually sports during its full phase.”
Just like all the other full moons in the calendar, the May full moon also goes by many different names. Popularly called the “Full Flower Moon,” the full moon of May was also dubbed the “Mother’s Moon,” the “Milk Moon,” the “Corn Planting Moon,” the “Hare Moon,” and the “Budding Moon.”
Though very different, depending on the community where these names originated in Native American and Colonial times, all of these monikers share a common theme: fertility and abundance.
“The May full Moon marked a time of increasing fertility, with temperatures warm enough for safely bearing young, a near end to late frosts, and plants in bloom,” details The Old Farmer’s Almanac in a separate article, one devoted to the 2019 full blue “Flower Moon.”