In this image provided by NASA, the Artemis II crew captured this view as the Earth sets behind the Moon during a lunar flyby, Monday, April 6, 2026. (NASA via AP)
A unique lunar event, featuring a rare blue moon, is set to occur on Sunday (May 31, 2026), according to science experts and the U.S. space agency NASA. The moon will be both a “micromoon” and a blue moon. A calendar blue moon typically occurs once every two to three years.
This will be the first calendar blue moon since August 30, 2023. Moreover, tonight’s blue moon will also be a micromoon, meaning it will appear slightly smaller than a regular full moon. Scientists attribute this to the Moon being at its farthest point from Earth in its orbit. However, the difference is unlikely to be noticeable to the naked eye.
Also Read : What is a minimoon?
The last blue moon that was also a micromoon was observed in October 2020, according to space experts.
What is a blue moon?
The term “blue moon” has been used for centuries, although its modern astronomical definition emerged only in the 20th century. A second full moon in a calendar month is commonly called a blue moon. Astronomers also use the term “seasonal blue moon” for the third full moon in a season that contains four full moons.
The effects of these eruptions, combined with other climatic factors, lowered global temperatures by an estimated 0.4-0.7º C in 1816, creating what became known as the “year without a summer”. Dust and other particles lingering in the atmosphere may have caused the moon to appear blue. This phenomenon is unrelated to the modern calendrical definition of a blue moon.
Following the eruption of Krakatoa in 1883, observers around the world reported blue moons and green-tinted suns. But despite the name, blue moons do not appear to be blue in colour.
The phrase “once in a blue moon” has been used for centuries to describe something that happens very rarely. The modern definition of a blue moon as the second full moon in a calendar month became widely known in the 20th century after an interpretation of material published in the Maine Farmers’ Almanac. August 2023 featured such a blue moon.
When it will be spotted in India?
The full moon will be visible across India on the night of May 31, weather permitting.
Like many full moons, it may appear orange when it is near the horizon before appearing brighter and whiter higher in the sky.
Difference between a blue moon and a micromoon
A blue moon and a micromoon refer to different lunar phenomena. A blue moon is the second full moon within a single calendar month, a relatively rare event that occurs every two to three years. The phrase “once in a blue moon” reflects this rarity.
Read More : Earth captures new ‘mini moon’
A micromoon, by contrast, occurs when a full moon coincides with the Moon being near its apogee — the farthest point from Earth in its orbit. As a result, it appears slightly smaller and dimmer than an average full moon.
In short, a blue moon is a calendrical designation for a relatively rare full moon, while a micromoon describes a full moon that occurs when the moon is near its farthest point from the earth.
Published – May 31, 2026 02:46 pm IST
