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NOAA - 08/2023


This week, a quirky mixture of science, hyperbole and folklore will cause millions of people to go outside and stare at the sky. We're talking about the Super Blue Moon. This is what it will look like:

Above: A "supermoon" over Cape Cod on Oct. 15, 2016. Credit: Chris Cook.

First, the science: The full Moon on Wednesday, Aug. 30th, is the biggest and brightest of 2023. Astronomers call it a "perigee moon." The Moon's orbit is an ellipse with one side ("perigee") about 50,000 km closer than the other ("apogee"). Full Moons that occur on the perigee side of the Moon's orbit seem extra big and bright. That's what is happening this week.

Next, the hyperbole: About 10 years ago, science journalists and even many astronomers started calling perigee Moons "supermoons." A supermoon is about 8% bigger and 15% brighter than an average full Moon. Would you call Clark Kent "super" if he were only 15% stronger than an average human? No, but let's roll with it!

Finally, the folklore: According to modern folklore, a Moon is "blue" if it is the second full Moon in a calendar month. August already had one full Moon (Aug. 2nd); now it is about to have another (Aug. 30th). The Moon won't literally turn blue, however, unless a volcano erupts at the same time.


In summary, this week's Super Blue Moon will be about 15% more gorgeous than an average moon. Go out after sunset on Aug. 30th, look east, and watch it rise into the darkening summer sky.

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