Celestial News: Total Eclipse of the Blue Snow Super Moon
January 4, 2018
A most unusual celestial event will unfold in the predawn hours of Wednesday, Jan. 31, while most folks are just beginning to stir for their morning activities. The full moon will be gliding through the shadow of the Earth for the only total lunar eclipse visible from Colorado in 2018.
The second full moon of the winter season traditionally is called the Snow Moon. As it so happens, this year's Snow Moon also is the second full moon in the month of January, the first one being the full Wolf Moon that occurred on New Year's Day. By one popular definition, this makes the 2018 Snow Moon also a Blue Moon.
Most of the time, we experience 12 full moons in a year, three in each of our four seasons. Each of these full moons has a traditional name from folklore and Native American tradition. Winter has its Wolf, Snow and Worm moons. Spring has its Egg, Flower and Strawberry moons. Summer has its Thunder, Green Corn and Fruit moons. Autumn has its Harvest, Hunter and Beaver moons.
But, the interval of time between full moons is about 29 and ½ days, just shy of a 30-day month, so, the date of the full moon slowly moves backward through the months. If a full moon occurs early enough in a new year, then there is room to fit in a 13th full moon, which means that one of the seasons will get an unusual fourth full moon. What would it be called? There is no traditional name for such a wandering oddball full moon. Calendar makers of yesteryear simply referred to the third full moon in a season with four full moons as a Blue Moon. This was the original meaning of the Blue Moon designation.
In 1946, a misprint in an article appearing in the popular astronomy magazine, Sky & Telescope, suggested that the second full moon falling in any calendar month would be considered a Blue Moon. This unintentional new definition caught on and stuck with a tenacity that would make any duck on a June bug proud.
And, so it is that we have two different definitions for the term Blue Moon.
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January's Blue Moon sets up an even more unusual situation that happens even less frequently than, um, once in a blue moon. That's because February, with only 28 days most years and 29 days in a leap year, can never have a Blue Moon, by the second definition. The next full moon after Jan. 31's Blue Snow Super Moon falls on March 1. The full moons skip over February completely in 2018. That sets up a second full moon in the month of March this year for a double Blue Moon in 2018. The last time this happened was in January and March of 1999.
"Big whoop," you might say.
It's true. Blue moons are really non-events, other than being an unusual fluke of the calendar. You won't look up and notice anything special about a Blue Moon.
You might, however, look up and notice something unusual about a Super Moon.
A Super Moon is the term used to describe a full moon that occurs when the moon is also near its perigee, or closest point to the Earth in its orbit. According to the website timeanddate.com, that makes a Super Moon appear about 14 percent larger than a Micro Moon and about 7 percent larger than the average full moon.
On Jan. 31, the moon becomes full at 6:27am, only 28 hours after passing its perigee and qualifying it as a Super Moon.
Is that enough to be noticeable to the naked eye? If the Micro and Super moons were side-by-side in the sky, the difference would be obvious, but put either by itself in a wide-open sky and it's doubtful that most folks would be able to discern the difference.
One thing that everyone can easily discern is when the full moon is totally eclipsed and when it is not. January's Blue Snow Super Moon will turn blood red just before dawn on the 31st when it is totally eclipsed by the shadow of the Earth.
When you go to bed Tuesday, Jan. 30, the full Snow Moon will be shining full strength through your bedroom window. Then, at 4:48 a.m. Wednesday, the Earth's dark shadow will take a bite out of the moon's upper left edge. Little by little, the shadow will engulf the moon until, by 5:51 a.m., the Blue Snow Super Moon is completely swallowed up, leaving only a blood-red ghost of a full moon in its place.
The red color is basically the same thing as the alpenglow that you sometimes can see on the snowy mountaintops just after the sun goes down. If the mountains don't get in the way, the sunlight streams through Earth's atmosphere and out the other side, illuminating the moon with red alpenglow instead of the mountaintops.
For folks living in northwest Colorado, totality begins when the moon is hovering only about one hand span over the western horizon. Shortly thereafter, the first rays of dawn will begin to color and brighten the sky. Totality ends at 7:08 a.m., less than 10 minutes before sunrise and only 14 minutes before the moon sets. It will be an interesting challenge to see how long you can keep the totally eclipsed red ghost of the Blue Snow Super Moon in sight as the sky brightens and the stars disappear in the approaching dawn.
At the onset of totality and before dawn has a chance to steal the darkness, look for the fuzzy glow of the Beehive Star Cluster, just to the right of the Blue Snow Super Moon's red ghost. Ordinary binoculars will enhance the view of both the eclipsed moon and the glittering star cluster.
Jimmy Westlake's “Celestial News” column appears monthly in the Steamboat Today. Check out Westlake's new 2018 Cosmic Calendar of sky events on his website at jwestlake.com. It features twelve of his best astro-photos and a day-by-day listing of cool celestial events that you and your family can enjoy watching all year.