BATON ROUGE, LA (WAFB) - We begin Wednesday, January 31 with a rare lunar trifecta: an astronomical event that hasn't occurred since 1866. It's the "Super Blue Blood Moon!"
But what does "Super Blue Blood Moon" mean? Let's break it down for you.
The Super Moon:
All by itself, a "Super Moon" is relatively uncommon. It is a full Moon that occurs when the Moon is nearest to Earth and its orbital path.
The Moon's orbit around Earth is elliptical: slightly oval rather than perfectly round. Given such an orbit, there are times when the Moon is closer to earth than average (perigee) and times when it is farther away than average (apogee). With the Super Moon, the full Moon is in perigee, which means the Moon appears slightly larger than average and is often brighter than average (if the skies are clear).
The Blue Moon:
No, the Moon is not blue: in fact, it will have a red tinge to it during this event.
The "Blue Moon" refers to the modern definition of a second full Moon occurring in a calendar month. We had a full Moon on January 1 (Sometimes called the Wolf Moon) and Wednesday's full Moon (sometimes called the Snow Moon) will mark the second for the month.
So why the term "blue?"
The exact reason remains under debate, but some language experts believe that it is the modern Anglicized word for belewe, an old English term which roughly translates to "traitor."
Okay, that doesn't make a lot of sense at first. But there is at least one chronicled mention of the "traitor moon" which referred to an unusual occurrence of a full Moon. There are typically 3 full Moons in a season, but once every 2 to 3 years, we get an event like this month: 4 full Moons in the same season.
Still, why "blue?"
A number of Christian holidays were once determined by the relationship between the seasons and the full Moons. Easter remains one of the most notable examples: even today, Easter is determined as the "first Sunday after the first full Moon, after the Spring Equinox." That is a mouthful but it does explain why the date for Easter can float from late March to late April.
So how does this play into the theory of the "belewe" Blue Moon?
Here is the linguists' theory: the "traitor" Moon, or "deceiver" Moon, occurred in those years when there were 4 full Moons in the spring. That meant that Easter in those years would not occur after the typical third full Moon of spring, but instead Easter came after the fourth spring full Moon. This meant that Lent didn't conclude until the fourth spring full Moon rather than the normal third spring full Moon.
In this older (original?) definition of the "belewe" Blue Moon, the technical definition of a Blue Moon was the third full Moon in a season with four full Moons.
In the end, it really doesn't matter much. The frequency of Blue Moons, regardless of definition, is roughly the same: once every 2 to 3 years.
The Blood Moon:
This definition effectively defines the lunar eclipse: when the Earth is between the Sun and the Moon and blocks the direct light from the Sun to the Moon's surface.
Everyone knows the Moon doesn't emit light, it simply reflects sunlight. So the question is often asked, "If the Earth is blocking direct sunlight to the Moon's surface, why doesn't the Moon just go dark?"
You have noticed that when the Sun is low in the sky, it tends to have an orange/red hue. This is the effect of the Earth's atmosphere. The effective thickness of the atmosphere is much deeper when the Sun is close to the horizon as compared to when it is overhead, and this added "thickness" plays with the colors. Gases and particles in the Earth's atmosphere scatter light, and they do a better job scattering violets and blues then they do oranges and reds. As a result, as the Sun gets closer to the horizon (sunrise or sunset), more oranges and reds make it to our eyes while the blues tend to be scattered away, given the sun that orange/red look.
The oranges and reds also pass through the Earth's atmosphere and back out to space. At the same time those wavelengths are "bent" (refracted) by the Earth's atmosphere and some of those oranges and reds still manage to strike the Moon's surface. Hence, we see a red/orange or "blood" moon.
In the end, we have three uncommon lunar/astronomical events occurring at precisely the same time, making for an event that hasn't occurred in more than 150 years.