Winter solstice 2018 brings a wonderful weekend of night sky wonders—a full Moon, a meteor shower, and a beautiful conjunction of planet Jupiter and Mercury. Here’s all you need to know.
The winter solstice, of course, is one of the biggest and most ancient annual events. We also call it the December solstice, since December 21st marks the start of summer for our Kiwi and Aussie friends, and everyone else in the southern hemisphere.
A Two-for-One Deal
The winter solstice—marking the longest night of the year (with the least daylight)—is Friday. If you want to be precise, the solstice happens at 5:23 p.m. EST. That’s the moment when our tilted planet’s northern axis tips maximally away from the Sun. As a result, the sun is low in the sky, which makes its rays as weak as possible.
The Full Moon rises at 12:49 P.M. Saturday, so it will certainly appear big, bright, and full both Friday and Saturday nights. Traditionally, December’s Moon was called the Cold Moon or the Long Night Moon—as it is visible during the longest night of the year. The names originate from the Native American tribes. Learn more about the Full Cold Moon.
How often does the winter solstice and full Moon happen on the same day? Not often. The next time this occurs is 2094. The last time the December solstice and full moon happened less than a day apart was in 2010, and the next time will be 2029. See the article, “A Full Moon on the Winter Solstice.”
The Ursid meteor shower will peak on the nights of December 21 and 22. This is a minor shower but if you want to catch a shooting star, see viewing details on our Meteor Shower Calendar.
And a bonus: Planets Mercury and Jupiter will pair up on the winter solstice, too! ! Look for their beautiful conjunction 10 degrees high, 40 minutes before sunrise. See my December Sky Watch for more details.
Oddities of the Winter Solstice
The solstice itself occurs at the same instant everywhere on Earth. That said, the clock time depends on your time zone: 5:23 P.M.ET Friday, 4:23 P.M.CT, 3:23 P.M. MT, and 2:23 P.M. PT.
Friday is also when the rising Sun pops above the southeast horizon as far to the right as is possible. And it sets as far left as can ever be seen. This throws sunlight into our windows at angles not observed any other day of the year.
If we were to list the most widely known solstitial realities, they are:
the fewest minutes of daylight,
lowest noontime Sun,
longest midday shadow of the year.
If we want to specify the solstitial property that’s least well-known, it is:
The odd fact that the Sun moves across the sky along its steepest downward arc. This means that its path that day has the shape of a rainbow. By comparison, the sun’s path on the equinox is a straight line across the heavens. Conversely, during the June solstice, the sun describes an enormous, high-up, smile-shaped trajectory.
The very fact that, while the solstice is indeed the date boasting the greatest darkness, it is not the day with the darkest afternoon. That event, meaning our earliest sunset, happened two weeks ago on December 7. And the darkest morning is yet to come, the first week of January.
Explaining why those milestones don’t happen on the solstice is a bit complicated and requires illustrations involving the analemma, and we will do that someday, I promise.
In the meantime, bang those drums, perform those sacrifices, and whatever other rituals your local municipal ordinances permit, as you celebrate this day in which sunlight finally stops shrinking.
Indeed, the very word solstice means: the sun stops.