What is a blue moon? Everything to know before the upcoming celestial event
A blue moon, defined as the second full moon in a single calendar month, will occur this weekend, with its peak visibility at 4:45 a.m. EDT on Sunday, May 28. This event will also coincide with a micromoon, where the moon is near its farthest point from Earth, roughly 252,334 miles away, though the difference in size will be imperceptible to the naked eye.
The second full moon of May will rise as a blue moon, a term used to describe the occurrence of two full moons in a single month. This celestial event happens approximately every two to three years and will peak at 4:45 a.m. EDT on Sunday, May 28, according to EarthSky. Unlike its name suggests, the moon will not appear blue but will retain its usual silvery-white or golden hue. This blue moon will also be a micromoon, meaning it will be near its farthest point from Earth in its orbit, around 252,334 miles away, compared to its average distance of 238,855 miles. While this places it about 10% farther than usual, the difference in size will be difficult for the unaided eye to detect, as noted by Dr. Pamela Gay, senior scientist at the Planetary Science Institute. The term 'blue moon' originates from the 1937 Maine Farmer’s Almanac, though the phrase dates back to the 1500s, historically used to describe something rare or impossible. While the moon itself won’t appear blue, rare atmospheric conditions—such as smoke or dust particles wider than 900 nanometers—can cause it to take on a bluish tint, as observed after the 1883 eruption of Indonesia’s Krakatoa volcano. The last calendar blue moon occurred in August 2023, and this year’s event will be the most distant full micromoon. Viewers can expect the moon to rise fully illuminated, though its apparent size will remain nearly indistinguishable from a typical full moon.
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