[Total lunar eclipse. Courtesy NASA]
Prepare to be inundated with lunacy this week, thanks to three interesting configurations of our nearest celestial neighbor. Wednesday the 31st is the second full moon of January, making it the so-called “blue moon” (as in “once in a blue moon”). But just how rare is a blue moon? Not very, if you consider that the time between two consecutive full moons is about 29.5 days, and all months except February have more than 29.5 days in them. For example, March 2018 also has two full moons.
The “blood moon” descriptor refers to a total lunar eclipse. When the sun, earth, and moon line up in that order in a straight line, the earth casts a shadow on the otherwise full moon. Because the red portion of sunlight refracts or bends through our atmosphere, the full moon doesn’t turn black but a coppery or bloody red. While it can be a startling sight to those who aren’t expecting it (I remember being scared to death as a child when I saw a lunar eclipse during a late night potty break), there is nothing bloody or gruesome about the event. On average one or two total lunar eclipses occur each calendar year. The January 31 total lunar eclipse will not be visible from here in Connecticut, as the moon will be setting as the eclipse begins. Our next chance to see a “blood moon” will be January 21, 2019.
Well, what about the so-called “super moon?” This refers to the full moon looking larger than average. Because the moon’s orbit around the earth is not a perfect circle, when the moon is at its closest point to earth (called the perigee) it looks 14% larger than when it is at its farthest point (called apogee). When this happens at the time of full moon, you might notice that the moon looks a little bit brighter than average. There is no scientific definition of a super moon (because it’s not really something that scientists care about, to be honest), but one running definition on the internet is that it is when the full moon occurs within a few days of perigee. So how rare is this? Considering that the first full moon of January 2018 (which occurred on New Year’s Day) was also a “super moon,” you have your answer.
Putting all three of predictable, cyclical configurations together into one event, however, is just a tad more rare. The last “blue-blood-super moon” was probably in 1866 (again, depending on your definition of “super moon”). So if you want to take this opportunity to go outside and gawk at dear old Luna, please be my guest. Just don’t howl, because you might be mistaken for a super blue werewolf!