Hope for a clear sky this next Wednesday the thirty-first. That is because there will be a full moon. But this is not your typical full moon.
This will be a Full Moon, Blue Moon, Supermoon, and if the sky is clear, a partial lunar eclipse.
As most everyone knows, a full moon occurs about once a month. Actually, it is every 29.5 days. And each month’s full moon has a name. January’s full moon, for example, is known as the Full Wolf Moon. But that came on January 2. Occasionally we may have two full moons in a month. If so, the second is referred to as a Blue Moon.
I have never heard a definitive explanation as to how they came to be called Blue Moons. One explanation, however, is that it is a mistranslation from the Old English term blewe, b-l-e-w-e, which had two definitions, one was the color blue, the other was “to betray” implying two full moons in a month betraying the typical one.
This full moon is also a supermoon. The term supermoon was coined a few years ago to refer to a full moon that occurs when the moon is near it closest approach to the earth.
The moon looks bigger when it is close to the earth’s surface, as opposed to high in the sky. That is a well-known illusion called the moon illusion. The moon, of course is still the same size.
But the moon does not orbit the earth in a circular orbit. The orbit is elliptical. The average distance between the earth and moon is around 239,000 miles. However when the moon the furthest away from the earth it is out there,252,000 miles. At its closest point it is about 225,000 miles away. So there is a difference of about 27,000 miles., which is enough of a distance to actually make the moon look a different size.
Some say a supermoon is around14% larger and 30% brighter compared to when the moon is farthest from the earth. At least those are the values I have seen comparing the closest point (perigee) and furthest point (apogee). I suppose you could call a full moon furthest away a minimoon or a micromoon, but that doesn’t have much pizzazz.
As for the eclipse, we should be able to see a partial eclipse on the thirty-first during the early morning hours before sunrise. Say around 5:00-6:00. However, the moon will set before the show is completed. Check your local news sources for the specifics for your area.
Chuck Lura
Natural North Dakota is supported by NDSU Central Grasslands Research Extension Center and Dakota College at Bottineau, and by the members of Prairie Public. Thanks to Sunny 101.9 in Bottineau for their recording services.
