Weather Education

Supermoon Facts and Misconceptions

You know what the moon is but what's a supermoon? Miriam-Webster dictionary defines the word super as exhibiting the characteristics of its type to an extreme or excessive degree. From that you can figure out that a supermoon is one that is much bigger than normal, but how much bigger?

A Supermoon is a recently-popular term to describe the regular cycle of perigee full moons. The moon’s orbit around Earth is not a perfect circle so at times the moon is a little closer (perigee), and other times a little farther away (apogee). Many reports mistakenly refer to a supermoon being 14% bigger and up to 30% brighter than average. The total difference between perigee and apogee is about 14% so a supermoon appears about 7% larger than average while an apogee (micro)moon would be about 7% smaller than average. A supermoon is also brighter because it is closer.

There is no universal astronomical definition of supermoon. By some definitions, there may be several to half a dozen supermoons every year, so it’s really not that super!

The difference between one supermoon and another may be the difference of dozens of miles, hundreds of miles or a few thousand of miles but that's all compared to something that is far over 200,000 miles away from Earth!

Take a picture of a supermoon with your smartphone and you'll notice it won't look much larger than usual. A lot of the pictures you see in social media and on TV of a supermoon are taken with a telephoto lens so that automatically makes it seem large. Many of us tend to focus on the moon when it is straight in front of us, near the horizon. Our eye compares the size of the moon to things on the horizon so that too makes it seem large. Here's an excellent explanation for why the moon seems so big when it rises.

Here are some other moon facts:

1. Any full moon may appear orange or red when it rises as the dust and particles in the path of light through the Earth’s atmosphere filter out shorter wavelength colors to give the moon a tint.

2. The lunar cycle is 29.5 days. That’s why we can have two full moons in one calendar month. The second full moon is often called a blue moon but it is not actually blue. The name comes from folklore.

3. Each full moon also has a name given by different cultures, religions, and folklore but those names also don’t match the color. Here’s a list of common full moon nicknames.

4. Supermoons have always occurred and always will.

5. Sometimes the distinction between one supermoon and another is just dozens of miles distance for something that is over 200,000 miles away.

What about the colors of the moon? 

Particles in the atmosphere like dust, pollution, pollen, smoke and even water droplets do tint the sun and moon. Typically when the sun and moon are high, they appear white. The light passes through a thin layer of atmosphere. When they are low in the sky they pass through much more air and that filters the colors to allow the dominant colors of red, orange, and yellow to be more prominent.

If you've taken a picture of the full moon and noticed a bright object in the picture that you didn't see in the sky, here's what it probably was.


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