On Monday, August 19, 2024, at precisely 2:26 pm ET, skywatchers will be treated to a rare astronomical event - a Blue Supermoon in the sign of Aquarius. This full moon is not just any full moon; it’s a Blue Moon, a phenomenon that adds a touch of mystique to the night sky.
What is a Blue Moon?
A Blue Moon is a special type of full moon that falls into one of two categories. The more familiar occurrence is when two full moons appear within a single calendar month. In this case, the second full moon is dubbed a “Blue Moon” or a “calendrical Blue Moon.” Another type is a “seasonal Blue Moon,” which is defined as the third full moon in a season that has four full moons, rather than the usual three.
Science behind the Blue Moon
The moon’s cycle lasts about 29.5 days, just slightly shorter than the average length of a calendar month. Because of this, occasionally, a full moon will appear at the very beginning of a month, allowing time for a second full moon to rise before the month ends—this is when a Blue Moon occurs. Blue Moons are not as uncommon as the phrase might suggest; they typically happen every two to three years.
Is the Blue Moon actually blue?
Despite its name, a Blue Moon doesn’t usually appear blue in color. However, under certain atmospheric conditions—such as those following large-scale forest fires or major volcanic eruptions—the moon can take on a blueish hue. This rare color shift occurs when ash particles in the atmosphere scatter red light, leaving the moon with a blue-green tint.
August Blue Moon
This August’s Blue Moon is a seasonal one, the third of four full moons between the summer solstice and the fall equinox. Such seasonal Blue Moons are even rarer than their monthly counterparts. After this celestial event, the next Blue Moon won’t grace the skies until May 31, 2026, when it will appear in the sign of Sagittarius.
The origins of the term "Blue Moon"
The term “Blue Moon” has an intriguing history, often linked to an old English phrase meaning “to betray.” According to The Farmer’s Almanac, the moon may have been considered “belewe” or "blue" because it betrayed the usual expectation of one full moon per month. Over time, the phrase came to signify something rare or unusual.
Interestingly, the term is also said to have roots in a 16th-century pamphlet by two friars who criticized the Roman church, arguing that people were gullible enough to believe even the most absurd statements, such as “the moon is blue” or “the moon is a ball of cheese.”
A supermoon experience
This Blue Moon is also a Supermoon, which means it will appear larger and brighter than a typical full moon because it occurs when the moon is at its closest point to Earth in its orbit. This combination of a Blue Moon and a Supermoon makes the event on August 19 an extraordinary sight worth stepping outside for.
