What is a Blue Moon?
- A blue moon is the second full moon in a calendar month.
- That is unusual because the period from one full moon to another is about 29 1/2 days.
- So when two occur in the same month, the first of these full moons is always on the first or second day of the month.
- On average, a blue moon occurs once every 33 months or full moons, 41 times per century, or about seven times every 19 years.
- An even rarer event is when two blue moons happen in the same calendar year, which happens about four times per century.
- Sometimes, smoke or dust in the air can scatter red wavelengths of light, as a result of which the moon may, in certain places, appear more blue than usual.
- But this has nothing to do with the name “blue” moon, and the association of the colour with the term is unclear.
What is a Micro Moon?
- This refers to the apparent size of the moon as viewed from Earth.
- The moon is not always a constant distance away from the Earth.
- Its orbit around the Earth is elliptical.
- The moon is about 363,711 km away at its closest to earth, known as perigee. At apogee, or the furthest point, the moon is about 403,945 km away.
- If a full moon happens to occur close to its closest point, then we call that a supermoon. And if it’s close to its furthest point, then we call that a micromoon.
- A micromoon appears only about 14% smaller than a supermoon and about 6% smaller than a typical full moon.
How Rare is a Blue Micromoon?
- Blue moons occur every couple of years, and micromoons occur two or three times every year.
- A blue micromoon occurs about once every couple of decades.
- However, they aren’t regular, and two such events may occur closer together or further apart.
- No special equipment is needed to observe this blue micromoon, and it should be clearly visible in the absence of clouds.
