AstroCal – December 2023
Having recently flip-flopped our clocks with the end of Daylight Saving Time, we will not have to hear the endless debates about ‘should we keep DST’ or ‘should we drop DST’ until the next ‘spring ahead’ on March 10, 2024. Having previously shared my biased opinion that I would just as soon stay on DST year round, I couldn’t help but notice a recent statistic about the subject in The MIlwaukee Journal-Sentinel. According to the MJ-S, November ranks as the month with the highest number of car/deer crashes. The reason? The end of DST pushes their evening period of activity smack dab in the middle of ‘rush hour’ (or in the case of the northwoods, ‘commuting home from work’ in lieu of an actual ‘rush hour’). In other words, the deer/human commute schedules collide (pun intended). No matter how much I dislike how early nightfall comes and how long the darkness lasts, those of us in Ontonagon county have one advantage over our neighbors to the south. With the extension of the EST zone into the western Upper Peninsula reaching nearly half way across the CST zone, our twilight happens an hour later, by the local clock, than it does a mere 30 miles to our south in the WI/MI border counties.
As long as we started this AstroCal with time, we might as well mention the Winter Solstice which will occur at 10:27 p.m. EST on December 21. This marks the point where the vertical rays of the Sun reach 23.5 degrees south latitude, the line designated the Tropic of Cancer. Should you be located somewhere on the globe at that latitude, you would see the Sun directly overhead. For those of us in the Northern Hemisphere, the Sun will appear at its lowest point in our sky at astronomical noon. The end result is seven hours of daylight and 17 hours of darkness for our latitude (47 degrees north for Ontonagon). The three weeks on either side of the solstice give us by far our shortest daylight and longest night period. By the middle of January, we will already be noticing a slight lengthening of the daylight hours. Should you be one of the unfortunate people affected by Seasonal Affective Disorder (SAD), we might suggest a small investment in a certified ‘sun lamp’ to help chase away those winter blues.
Leaving the time and season change soap box behind, let us look at the Lunar Cycle for December. The first week of the month will see the previous cycle winding down. The Last Quarter Moon happens on Dec 5 and the last Old Crescent Moon will appear near the eastern horizon in Scorpius, the Scorpion 40 minutes before sunrise on Dec 11. The New Moon is slated for Dec 12 followed by the First Quarter Moon of the new cycle on Dec 19 and the Full Moon is set for Dec 26. If you are an avid seeker of the first glimpse of the New Crescent Moon, look for it hugging the western horizon on December 14 about 40 minutes after sunset.
Our historical Astro-event comes from a mere 38 years ago when one of the most famous comet’s known to humankind made a rather disappointing return to the inner Solar System. Since Halley’s Comet made its last close approach to the Earth in 1986, most of us haven’t given it much thought as it is only halfway through its current 76 year orbit. Nonetheless, the Abrams Planetarium reports, “Halley’s comet reaches aphelion early in December 2023. Aphelion marks the point in its orbit when it’s farthest from the Sun. Halley’s Comet will reach perihelion, its closest point to the Sun, in late July of 2061, just 38 years from now. Halley’s Comet’s 2061 appearance will be spectacular!”
As the much anticipated 1986 pass neared, a host of companies began marketing small telescopes that they were sure the general public would snatch up to join the cosmic fun. Apparently the hype about Halley wasn’t enough to compel people to fork over a hefty price for a once in a lifetime event. Less than a year later, I picked up one of the small table top units for less than a third of what they were asking prior to Halley’s return. I won’t mark the next pass down in my date book yet but it would give the (by then) 108 year-old me to look forward to!
If you are up for the challenge of locating planets Neptune, Uranus, and asteroid 4 Vesta, let us direct you to the excellent planet finder charts that appear at abramsplaetarium.org/msta/ .
As for the morning planets, Venus can be found in the SE shining brightly at mag -4.2. The planet will appear in conjunction (close to) the waning Crescent Moon two hours before sunrise on Dec 9. By the end of the year, Venus will be in its gibbous phase having filled out from 68 to 78 percent of a full disk. It will still dominate the morning sky even as the size of the disk shrinks from 17 to 14 percent during the month. Mercury will brighten to mat +1.0 by Dec 30 and can be located to the left of Venus. Observations of Mercury will improve greatly in January.
The evening sky will remain Jupiter’s domain even as it’s magnitude reduces slightly from -2.8 to -2.6 as the month passes. As Jupiter ends its retrograde motion against the background of stars, the size of its disk will also be shrinking fron 48” (arcseconds) to 44” across. Saturn will pass through the dusk skies, moving across the stars of Aquarius, the Water Bearer from S to SSW during December. The Ringed Planet’s magnitude will be a steady +0.9. Through a telescope, the rings will present themselves at about a 37 degree angle with about 10 degrees visible from edge on.
The Geminid meteor shower peaks on December 13-14 with up to 10 meteors per hour visible under ideal conditions. Geminid meteors are brief streaks of light emitted by plasma created as dust impacts the Earth’s upper atmosphere at a speed of 34 kilometers per second. The dust originates from the asteroid 3200 Phaethon.
It is always my intent to take some of the mystery out of these astronomical events so even those with a casual interest in the heavens will not need a reference manual at hand to understand the upcoming events. With that said, there are times when the astronomer geek in me likes to pass along items that can’t really be distilled into a few short sidebar explanations. There are actually two bits of information in the December Sky Calendar that I would like to pass along and in this case, I am going to let the good folks at Abrams Planetarium do the explaining:
AstroGeek item one: “Mercury passes ascending node of its orbit, moving north through the ecliptic on Dec 16 and passing perihelion on Dec 20, so transition through inferior conjunction Dec 22 is fast, enabling views in both evening and mornings this month!” [note – look for Mercury in the W 40 min after sunset early in the month and in the E 40 before sunrise at the end of the month].
AstroGeek item two: “Of the five first-mag stars within the zodiac, only Pollux [in Gemini – the Twins] can’t be occulted by the Moon, since it is 6.7 degrees north of the ecliptic. This month, the ascending node of the Moon’s orbit is 90 degrees west of Pollux, making the Moon come close to Pollux at each pass in 2023-24. Nodes of the Moon’s orbit regress all the way around the zodiac in 18.6 years, so 8-10 years from now, observers will be able to watch the Moon pass very widely south of Pollux.” Another thing to pencil into your long term appointment calendar!
Compiled by Ken Raisanen of WOAS-FM – information provided by Abrams Planetarium Sky Calendar, Michigan State University. More information and subscription information can be found on their website at http://abramsplanetarium.org/skycalendar/ or on X (formerly Twitter) at http://twitter.com/AbramsSkyNotes. Yearly subscriptions cost $12 and can be started anytime.
Top Piece Video – As long as we started talking about time – here is a clip of a 1986 Fillmore reunion concert featuring The Chambers Brothers and their mega hit Time Has Come Today – hey, you have to love the cowbell!