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Once In a Blue Moon

Updated: Dec 12, 2023

The common expression “once in a blue moon” become a reality for some as on Wednesday, August 30, we caught a glimpse of a rare celestial event, the Super Blue Moon.

Supermoon Zimbabwe
Blue Moon in Zimbabwe

According to NASA, a blue moon is when we see the full moon twice in a single month. The moon’s cycle is 29.5 days, so shorter than the average length of a calendar month. Don’t take the name too literally though. The moon will not be blue. However, on rare occasions, tiny particles in the air, typically of smoke or dust, can scatter away red wavelengths of light, causing the moon to appear blue.

This Blue Moon will be a supermoon, meaning the moon is closer to earth than is normal. It is the third of four supermoons in a row and is said to be the biggest, and closest full supermoon of 2023.

This coincides with planet Saturn, that can be seen in the sky near to the moon, also in her planetary position closest to the earth for 2023. According to NASA, a full moon occurs approximately once a month, but it is not always perfectly full due to the rotation, which means that we always see the same side of the moon. The moon is only 100% full when the moon, Earth, and sun are perfectly aligned, which can result in a lunar eclipse.

How rare is a blue moon?

For a monthly Blue Moon to take place, a Full Moon must occur at the beginning of the month. This is because the time between two successive Full Moons is approximately 29.5 days, just short of most months in the Gregorian Calendar.

Seasonal Blue Moons take place slightly less frequently than monthly Blue Moons. In the 1100 years between 1550 and 2650, there are 408 seasonal Blue Moons and 456 monthly Blue Moons. This means that either type of Blue Moon occurs roughly every two or three years.

Blue Moons that are blue are incredibly rare and have nothing to do with the calendar or the Moon's phases but are instead a result of atmospheric conditions. Volcanic ashes and smoke, water droplets in the air, or certain types of clouds can all contribute to a Full Moon taking on a blue shade on rare occasions.

Latest Blue Moon August 31

Size and Brightness

During a super blue moon, the moon can appear up to 14% larger and 30% brighter than a regular full moon. This is due to its closer proximity to Earth. The moon can sometimes appear еvеn larger when it's close to the horizon due to an optical illusion known as the "moon illusion". This phenomenon occurs because our brain compares the moon to familiar objects on the ground.

This time, it will be the year’s closest full moon, just 357,344km (222,043 miles) or so away. That is more than 160km (100 miles) closer than the August 1 supermoon.

Not the Same Worldwide

The Moon reaches its various phases at specific moments. But because of time zones, the local time of a Full Moon can differ from one location to another. For instance, the recent Blue Moon took place at 01:35 UTC on August 31. Locations in time zones that are at least 1:30 hours behind UTC, including New York City, Rio De Janeiro, and Vancouver, saw their Full Moon take place on August 30, 2023.

Blue moon origin

The definition of a seasonal Blue Moon, the third Full Moon in an astronomical season with four Full Moons, can be traced back to the now-defunct Maine Farmer's Almanac. According to the Almanac, the appearance of a 13th Full Moon in a year upset the arrangement of Church festivals. The unlucky status of the number 13 and the difficulties of calculating the occurrence of such a Full Moon led to the extra

Full Moon being named a Blue Moon.

We can thank the Christian ecclesiastical calendar for the reason why the third Full Moon of the season is called the Blue Moon. The calendar uses the phases of the Moon to determine the exact dates for holidays like Lent and Easter.

The month of Lent contains the final Full Moon of winter, Lenten Moon. The first Full Moon of spring, also known as the Easter Moon or the Paschal Moon, falls just before Easter. Naming the third Moon of the season as the Blue Moon ensured that Lent and Easter coincided with the right Moon phases, and other celebrations and customs would still fall during their “proper” times.

Super Moon

Saturn near the blue moon

5 Degrees to the moon’s upper right at sunset in the east-southeastern sky, you would have noticed a visible bright point, the ringed planet Saturn, which appeared to circle clockwise around the moon as the night wore on.

You don’t need any optical aid to enjoy that lovely pairing of the moon and Saturn. At their closest, the duo were two degrees, the width of four full moons, apart.

Saturn just reached opposition

At opposition, the ringed planet shines at its brightest for 2023, at magnitude 0.4. It’s also when Saturn is at its least distance from Earth for 2023. It’s 73 light-minutes (about 8.8 astronomical units) away.

Saturn’s disk size is largest now, appearing 19 arcseconds across. And Saturn’s rings are tilted by 8.1 degrees, relative to earthly viewers. They span 44.2 arcseconds.

Thus, opposition marks the middle of the best time of year to see Saturn, or any outer planet. And any small backyard telescope will show the rings of Saturn.

Here are some interesting facts you need to know about the Sturgeon or Blue Moon on Wednesday:

  • In astronomy, a season is the period between a solstice and equinox, or vice versa. Each season, winter, spring, summer or fall lasts three months and usually has three full moons, occurring about 30 days apart.

  • All full moons are opposite the Sun, as viewed from Earth, rising fully illuminated at local time around sunset and setting around sunrise.

  • Generally, Blue Moons occur every two to three years. The last Blue Moon was on October 31, 2020, the night of Halloween.

  • When a blue-coloured moon happens, the blue colour is the result of water droplets in the air, certain types of clouds, or particles thrown into the atmosphere by natural catastrophes, such as volcanic ash and smoke.

  • Blue Moons that are blue in colour are extremely rare and have nothing to do with the calendar or the Moon’s phases. They don’t have to be full moons either.

Blue Moons 1940 – 2060

April 30, 1942

October 31, 1944

August 31, 1947

May 31, 1950

December 31, 1952

October 31, 1955

July 30, 1958

January 31, 1961

April 30, 1961

November 30, 1963

August 31, 1966

May 31, 1969

December 31, 1971

October 31, 1974

July 30, 1977

March 31, 1980

December 30, 1982

July 31, 1985

May 31, 1988

December 31, 1990

September 30, 1993

July 30, 1996

January 31, 1999

March 31, 1999

November 30, 2001

July 31, 2004

June 30, 2007

December 31, 2009

August 31, 2012

July 31, 2015

January 31, 2018

March 31, 2018

October 31, 2020

August 31, 2023

May 31, 2026

December 31, 2028

September 30, 2031

July 31, 2034

January 31, 2037

March 31, 2037

October 31, 2039

August 31, 2042

May 30, 2045

January 31, 2048

September 30, 2050

July 30, 2053

March 31, 2056

October 31, 2058

Credit to NASA for the info & Steph Johnston from Zimbabwe for the Photos


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