Supermoon May Not Be So Super After All

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The supermoon you’ve been hearing about everywhere may fit the technical criteria for being a supermoon, but not everyone thinks it’s so super. In fact, we usually have three of them each year, so does anything about this weekend’s supermoon make it truly great? debunks a number of myths that have been circulating through mainstream media.

In case you’re wondering, Sunday’s full moon will happen at 2:09 p.m. Eastern, which means that Americans won’t actually get to see it right when it’s at its fullest. The technical term for the moon we will see is a waning gibbous moon.

Technically, a supermoon

The supermoon that will be visible this weekend fits the technical description of a supermoon. It is certainly this year’s biggest and closest full moon. It also fits the other criteria, which is that it must be either a new or full moon that occurs within 90% of its closest approach to Earth within a particular orbit. The technical term for this is perigee.

In 2011, the supermoon was especially spectacular, as it came within only 126 miles of its closest possible approach to Earth. That was closer than most of the more average supermoons, as this weekend’s one is. Technically, we had another suppermoon on July 13 and will have another one on Sept. 8 because they fir the official criteria.

Supermoon 14% larger?

According to, statements that Sunday’s supermoon will be 14% bigger than usual are wrong. The site states that it will actually only be about 7.2% bigger than usual, based on the moon’s mean distance from the Earth. Maybe the 14% comes from the distance between the Moon’s closest point to Earth compared to its furthest point. However, the difference of those numbers (we’ll spare you the math here), is apparently 12.4%.

The website states that the 14% number comes from an article published in the October 1989 issue of Sky and Telescope that gives the 14% number, which has apparently been floating around since then.

Brighter than usual?

Many have also been saying that this weekend’s supermoon will look 30% brighter than usual, but says this is another misconception. Doing the math using the distances of the moon and the sun, the website says this weekend’s supermoon will only be about 16.9% times brighter than the usual full moon. Instead, the website suggests that the 30% is actually from when the moon is at its furthest point from Earth, as that calculation ends up being about 30%.

So will tomorrow’s supermoon blow your socks off? says probably not. In fact, the site says it will look pretty much like any other moon except for those who happen to see the moon exactly when it is rising or setting.

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