Blue Supermoon 2023: Rare Celestial Event Guide

 On August 31, 2023, we'll witness a unique celestial spectacle, as a full Moon, a supermoon, and a blue Moon all coincide on the same day. This rare occurrence is referred to as a 'blue supermoon'. Let's delve into what this term signifies, and answer some frequently asked questions.

What exactly is a supermoon?

A supermoon transpires when the Moon is at its nearest point (perigee) to Earth during its elliptical orbit and coincides with a full Moon. But what's so special about a supermoon? For observers, it offers an enlightening experience. The Moon's orbit around Earth forms an ellipse, drawing it closer and farther from our planet. The farthest point of this ellipse is the apogee, approximately 405 thousand kilometers from Earth. When the Moon is at its nearest point, known as the perigee, it's around 363 thousand kilometers away. A full Moon at perigee appears slightly brighter and larger than a typical full Moon, giving us a supermoon.

What is the significance of a 'blue moon'? Does it change color?

"Once in a Blue Moon…" signifies rarity, if not absurdity. The last time you saw a blue Moon was probably never. On August 31, 2023, we'll have a "blue moon." As per contemporary folklore, a Blue Moon is the occurrence of a second full moon within a single calendar month. Usually, each month has just one full moon, but occasionally a second slips in. Given that full moons are separated by 29 days, and most months are 30 or 31 days long, it's possible for two full moons to fall within a single month. This event typically happens every two and a half years, on average. August 2023 will witness two full moons, on August 1 and August 31, the latter of which is classified as a Blue Moon. But will it actually be blue? The answer is no. The timing of a full moon doesn't influence its color. The moon on August 31 will retain its familiar pearl-gray hue, and owing to its supermoon status, "blue" should be interpreted as rare.

Do Blue Moons and Supermoons always coincide?

The answer is no. The term "supermoon" describes a full Moon that takes place roughly a day of perigee (or close), occurring three or four times annually. While about 25% of all full moons are supermoons, only around 3% are blue moons. The intervals between blue supermoons are inconsistent (potentially spanning up to 20 years), but on average, they occur every 10 years. The subsequent super blue moons are scheduled for January and March 2037.