The Celestial Sphere

By Mathew Johnson

The word “solstice” comes from the Latin sol (sun) and sistere (to not move). Thus “Winter solstice” means “Sun stands still in Winter.”

During the Earth’s revolution around the sun, two solstices occur, the summer one in June and the winter one in December. This year, the winter solstice occurs on Thursday, Dec. 21, at 10:27 p.m. On this day, the Northern Hemisphere experiences the shortest period of daylight, and thus the longest night. The North Pole is bathed in six months of darkness. The opposite occurs in the Southern Hemisphere.

On the 21st the sun will rise at 7:14 a.m. and slowly gain altitude until it reaches the meridian (due south, 180º S) at 11:48 a.m. The sun then begins to descend, setting at 4:23 p.m.

For those with an compass, on the 21st the sun will rise above the horizon at 121º ESE and will set at 239º WSW. When on the southern meridian (the highest the sun rises on a particular day) the sun will rise to only 25º above the horizon. Because the sun rises and sets at its most southern locations and rises only to its lowest height of the year, Norfolk will experience only 9 hours, 8 minutes, 31 seconds of daylight.

To compare with the summer solstice: This past June 21 the sun rose at 5:16 a.m., almost two hours earlier than at the winter solstice, and set at 8:28 p.m., four hours and five minutes later. June 21 had 15 hours, 52 minutes,12 seconds of daylight. 

Observable Planets

Because it is so close to the sun, Mercury is only visible just above the horizon either right before the sun rises or right after it sets. On Dec. 1, Mercury can be seen low in the southwest 30 minutes after sunset and about 5º above the horizon. It is visible until Dec. 11 in the same location. After that, Mercury begins to dim, and we lose sight of it by the 15th. 

Venus continues to be visible throughout December, rising before 4 a.m. as a brilliant gem in the east. On the 9th a slim crescent moon will be a few degrees south of Venus. As Venus moves through the constellation of Libra on the 17th, it can be observed a degree or so above Zubenelgenubi, Libra’s brightest star. By month’s end, Venus is just short of passing into the constellation of Scorpio, standing about 10º above its brightest star, the red giant Antares. 

Mars is too close to the sun to observe in December.

Jupiter can be observed nearly all night long as it moves through the constellation Aries. Jupiter is rising higher in the sky than it has since 2015 and is easy to spot, since it is so large and bright. Even with a small telescope the two dark bands straddling its equator are visible. Jupiter’s four Galilean moons, Io, Europa, Ganymede and Callisto, can also be seen through a small telescope or with binoculars. In larger scopes, Jupiter’s moons present opportunities to view transits and occultations. (Check on the internet for the times and illustrations of such events.) When our atmosphere is clear and still, Jupiter reveals startlingly fine details of its atmosphere, with the great red spot occasionally revealing itself. 

At twilight, Saturn is already high in the southern sky. You should look for it in the early evening, since it sets by 9 p.m. On Dec. 17, the crescent moon is just several degrees below Saturn, helping one located the ringed planet. Saturn is located in Aquarius. A planisphere is recommended to locate the constellations and planets that move along the celestial sphere. Saturn and its rings can be seen with binoculars and small telescopes. A few of Saturn’s larger moons are also visible with small scopes. To identify Saturn’s moons on any given evening, search the internet using a term like “Observing Saturn’s moons” and giving the date. You can also visit the NASA or U.S. Navy website. 

Uranus is visible very late into December’s night skies, but it is tiny and faint. However, the planet can be recognized against a field of stars, since it displays a distinctive blue/green color. This month, with moderate-sized binoculars, Uranus can be found halfway between the Pleiades star cluster (the Seven Sisters) and the planet Jupiter, both easily recognized. 

Comet

An observer with a small telescope, aided by Norfolk’s dark skies, can possibly view the comet Tsuchinshan 1. From Dec. 4 to 12 this comet is predicted to rise after 1 a.m. in the east, just above the bright blue white star Regulus, which is the brightest star in the constellation Leo. The best time to view Tsuchinshan 1 is after midnight from the 5th to the 16th. Viewing ends by the 17th when the light of the waxing moon begins to interfere. 

Meteor Showers

The Geminid meteor shower is predicted to be quite favorable this year with the peak of the shower occurring on the night of Dec. 14. The zenith hourly rate could reach 100 meteors per hour, making the Geminids the best shower of the year. It is active from December 4th to the 17th. The radiant of the shower, where most of the meteors will first appear, is located in the constellation Gemini, which is found to the left and above the easily located constellation of Orion.

Moon phases

Last Quarter: Dec. 5, left side of moon illuminated 
New Moon: Dec. 12, no moon visible
First Quarter: Dec. 20, right side of moon illuminated
Full Moon: Dec. 26

December’s full moon was known by Native American societies as the Cold Moon because this is the time of year when the winter air settles in and the nights become long and dark. This moon has also been known as the Long Nights Moon because of its proximity to the date of the winter solstice. 

You need a comfortable lounge chair, a prime goose down jacket, hand warmers, blankets and a thermos with a warm beverage to view the heavens during the winter months.