The astronomical forecast for Wednesday, August 30 calls for a blue supermoon.
Northeastern Global News interviewed Jacqueline McCleary, assistant professor of physics and observational cosmologist at Northeastern University, about what makes this moon the largest and brightest full moon of the year.
Why is it called the blue supermoon?
A blue moon and a supermoon are two different phenomena; This Wednesday’s full moon is remarkable because it will be both. Allow me to begin with the professor’s explanation.
A complete lunar cycle – new moon to new moon or full moon to full moon – lasts 29.5 days. If you want to impress your friends, the technical term for this cycle is a synodic month.
It is no coincidence that our calendar months, which have 28-31 days, roughly coincide with these lunar cycles. Therefore, most of the time you will only observe one full moon per calendar month.
However, since calendar months are a few days longer than a lunar cycle, there are instances when you can see a full moon at both the beginning and end of the month. This second full moon is commonly referred to as the “blue moon.”
will it look blue
Unfortunately, when the moon is blue, the moon does not take on a nice blue hue. In general, blue moons look just like any other full moon.
Why is it called the Blue Moon?
Beats me! As far as I can tell, this usage dates back to the Maine Farmer’s Almanac, which followed the tropical year (winter solstice to winter solstice).
They named each full moon and for some reason chose “blue” to denote the 13th full moon in a year.
How big will it appear compared to other full moons?
The moon’s orbit is slightly elliptical, deviating about 5.5% from a perfect circle. At the extreme point of its orbit, apogee, the moon is 405,500 kilometers from Earth. At the closest point, perigee, the moon is 363,300 kilometers away. When the moon is at perigee, it appears about 7% larger than average and 14% larger than at apogee. A full moon that occurs as the moon approaches perigee is called a “supermoon.”
When is the best time to see the blue super moon?
Although factors such as latitude and daylight saving time affect exact time, full moons generally reach their highest point in the sky (or “transit”) at midnight.
To see it, just look up!
However, the best time to see Wednesday’s Super Moon is actually at moonrise at 7:03 p.m. It will be easier for you to see how much larger it looks compared to objects on the horizon.
Is a Blue Supermoon a Super Rare Event?
Yes. Because the moon has a relatively short orbital period, supermoons are common, occurring about four to six times a year.
Blue moons are rarer, only occurring every 2.5 to 3 years.
But having both a super moon and a blue moon only happens every 10 to 20 years. If you miss Wednesday, or “weathered” as astronomers sometimes say, you’ll have to wait until 2037 to see the next one!
We keep our fingers crossed for clear skies.
Will you stay up to watch the moon transit?
Of course I’ll stay up and watch it! I’m an astronomer, so I’m a night owl anyway. But even if I wasn’t, there’s something special about seeing objects around you cast shadows under a bright moon.
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Written by Cynthia McCormick Hibbert.