The total lunar eclipse on January 31 merited many superlatives from media reporters. After all, no total eclipse had coincided with a blue moon for 152 years and a repeat coincidence will not occur again until 2037. The occurrence appropriately acquired the moniker “super blue blood moon” total lunar eclipse. Our current post provides additional clarity for the actual lunar eclipse event as it unfolded on January 31, 2018 as well as an explanation of its adjective-laden label.
Let’s dissect the terms super, blue, and blood moons that modify lunar eclipses. (A) Supermoons occur fairly often whether or not an eclipse occurs. Supermoons at FULL phase occur in consecutive order about three times per year. One of the three is sometimes dubbed an “extra close” supermoon because it comes within 357,000 km (about 222,000 miles) of Earth. Supermoons appear somewhat larger in the sky—having as much as 30% more sky area—because they come closer to the Earth in the Moon’s elliptical orbit. In addition, larger than normal NEW moons occur about three times per year because of Earth’s variable elliptical orbit. They are also called supermoons, but non-illuminated new moons are not visible in the sky owing to their proximity to the sun. The term “supermoon” has acquired a certain mystique, but actual supermoons are not very unusual.
(B) Blue moons acquired their romantic name merely by being the second full moon in a calendar month. Full moons take place about 29.5 days apart, so two full moons in any single month could only occur on days 1 and 30, 1 and 31, or 2 and 31 of any month. Blue moons occur about once every 2.7 years. Only 85 total lunar eclipses occur in the 21st century. It is easy to understand that it would be highly unusual for a total lunar eclipse to take place exactly on a day numbered 30 or 31 on which a full moon also occurs. This would be a calendar-related coincidence. The expression “Once in a blue moon” indicates a highly unusual or rare event.
(C) Finally, we explain the meaning of “blood” moon. This term is perhaps easiest to explain. During total lunar eclipses a little filtered light from the sun is bent around the earth through its atmosphere and falls upon the moon even though no direct sunlight reaches the moon. The filtered light is reddish in color. Thus, the term “blood moon” has become popular. The reddish glow is much dimmer than normal reflected moonlight, but is still beautifully visible during eclipse events. “Blood moon” is a term widely used for a total lunar eclipse, but it has acquired a mysterious meaning in some quarters.
On the early pre-dawn morning of Wednesday, January 31 my sunroom became the observational venue to watch the progress of the Super Blue Blood Moon Eclipse of 2018 and to write the first few sentences of this post. I noted the progress of the umbra, the total shadow of our home planet, slowly crossing the moon. The visual event began at 5:48 AM with a tiny cookie bite of darkness at one edge. By 6:51 AM totality had begun. I was blessed that the sky during this stage of the eclipse was reasonably clear. Two factors prevented me from seeing the totally eclipsed moon’s blood red color beginning at 6:51 AM. The sky was just beginning to become light in the pre-dawn morning and it had acquired a haze of thin clouds.
Watching the total shadow of Earth’s umbra slowly creep across the Moon’s surface inspires deep emotions. Humanity inhabits a planet which occasionally casts its eclipsing shadow on the Moon, Earth’s satellite a quarter million miles distant. One may directly perceive that Earth is a much larger body than our lunar companion as we watch the gentle curve of the shadow’s edge slowly creep across its surface. A palpable feeling of wonder, reverence and humility before our Creator grips the thoughtful, contemplative observer. We experience a unique sense of our location in the Solar System and the cosmos.