Although we have a Full Moon every month, the Sturgeon Moon (Full Moon of August) this year will be a special one. Here’s Why:
The Blue Moon
A Blue Moon is a Full Moon which is the 3rd Full Moon, when an astronomical season (Equinox to Solstice or vice-versa) has 4 Full Moons.
Given that the Full Moon of June occurred just 3 days after the Solstice, and the September Full Moon falling 2 days before the Equinox, we will have 4 Full Moons (June, July, August and September) in this as Astronomical Season. This makes the Full Moon of August a Blue Moon.
The ‘Pure’ Blue Moon
While we have defined the Blue Moon, many astronomical definitions like Blue Moon and Supermoon do not have a definition that is fixed. While a Blue Moon is the 3rd of the 4 Full Moon in a season, in months where there are 2 Full Moons, the 2nd Full Moon is also called the Blue Moon by some people.
This makes one Blue Moon happen, practically every year (when there are 13 Full Moons in a year).
For this reason, we call the Full Moons falling under the former definition, a ‘Pure’ Blue Moon.
The Rarest
Although some years have 13 Full Moons, during any Astronomical Season, i.e. between the June Solstice to September Equinox, or the September Equinox to December Solstice, or the December Solstice to the March Equinox or the March Equinox to June Solstice, there occurs 3 Full Moons.
So an Astronomical Season with 4 Full Moons is quite a rare occurrence. Once the Blue Moon of 22nd August 2021 passes, the next Pure Blue Moon will occur on August 19, 2024.
Not Alone
The 22nd of August 2021, is not only significant astronomically as the day of the Full Moon, but it is also the day of Conjunction and Close Approach (combined to form Appulse) of the Full Moon with Jupiter. As the Moon slowly moves towards the East, on this day, it passes 3°57′ to the south of Jupiter as they share the same Right Ascension (Conjunction) and approach the gas giant, with a separation of just 3°44′ (Close Approach).
So on the evening of 22nd August as you venture out to take a look at the Blue Moon, you’ll also notice Jupiter shining brightly with its own 4 Moons (not visible through naked eye) above the Bright Full Moon.
Not Really Blue
While the Full Moon is called the Blue Moon this month, It will NOT appear Blue or any shades of blue. However, as it rises from the southeastern horizon, it will appear orange, then turn into to a pale yellow moon as it rises higher, eventually turning into bright white.
The orange color comes from the Oxygen and Nitrogen molecules in the atmosphere of the Earth which block the Blue from the white light in the Moon’s spectrum, making it appear reddish, and therefore orange due to scattering.
Although we speak of Full Moon as if it is a day of the Month, in true astronomical sense, the Full Moon is a phase of the Moon, i.e. This is the period where the Moon will be in a proper alignment with the Earth and Sun, such that the face of the Moon is completely illuminated.
In August this Full Moon Phase will occur between 04:04PM to 05:57PM during which the Moon will be Illuminated on 99.8% of its disc.
However, the near-perfect straight alignment with the minimum angle between the Sun-Moon-Earth, which we call the Phase Angle, will be achieved at 02:27PM with a phase angle of 5° 11′ 04.5″.
So Enjoy the sight of the Full-Orange-Pure-Blue-Sturgeon-Moon on the evening of 22nd August, this weekend.
Check out our poster on the Full Moon
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