We have been hearing a lot about Supermoons lately, which sure makes them seem a whole lot less super. In fact, in 2016 we had a Supermoon in October, November, and coming up this week on December 14th. So, what are these Supermoons and how super are they, really?
As you hopefully know, the moon orbits around the Earth. What you may not know is that the moon’s particular orbit is not a perfect circle; it’s in the shape of an ellipse. And on top of that, one side of this elliptical orbit comes closer to the Earth than the other. So, over time, the moon gets closer to us and farther away from us, depending on where it is on its elliptical journey. A Supermoon is so-called because it describes a time when the moon is orbiting closer to us than usual, so the full moon looks bigger and brighter–30% bigger and brighter, in fact.
Can we really observe the size difference of Supermoons compared to an average full moon? Yes, but only when the moon is just starting to rise or is about to set. The apparent difference in size between a moon on the horizon and a moon high in the sky is due to the landscape features that give our brain a sense of scale (this scenario is also called Moon Illusion). When the moon is high in the sky, the size difference between an average full moon and a Supermoon is hardly noticeable.
November’s Supermoon was the biggest one since November 1948 and we won’t see a full moon that big again until 2034. December’s is unique because it will be so large and bright that it will mostly wipe out our view of the Geminid meteor shower.
In conclusion, I think Supermoons are pretty super and I encourage you to get out and see the last one of 2016 this week. For more information about how to see the December 2016 Supermoon, check out this article.
Want to nerd out a little more? Here’s a relatively concise description of this phenomenon from NASA:
“When the Sun, the Moon, and Earth line up as the Moon orbits Earth, that’s known as syzygy (definitely something you want to keep in your back pocket for your next Scrabble match).
When this Earth-Moon-Sun system occurs with the perigee side of the Moon facing us, and the Moon happens to be on the opposite side of Earth from the Sun, we get what’s called a perigee-syzygy.
That causes the Moon to appear much bigger and brighter in our sky than usual, and it’s referred to as a supermoon – or more technically, a perigee moon.”