Skywatch Line for Wednesday and Thursday, December 13 and 14, 2023
This is Dudley Observatory’s Skywatch Line for Wednesday and Thursday, December 13 and 14, written by Alan French.
The Sun rises at 7:17 A.M. on Wednesday and sets at 4:21 P.M. On Thursday it rises at 7:18 and sets at 4:22. This Thursday has just over 6 minutes less daylight than last Thursday.
The Moon was new on Tuesday and is now remerging in the early evening sky. Wednesday night a very young Moon sets only 21 minutes after the Sun and will be too deep in twilight to spot. On Thursday look for a slender, 5% illuminated Moon, just under 6 degrees above the southwestern horizon at 5:00 P.M. The Moon will be higher and brighter during the coming nights at it moves toward first quarter, which it will reach next Tuesday.
The Perseid meteor shower in August is best known. It is a rich shower, it occurs during warm temperatures for those of us in the northern hemisphere, and some people are on vacation and perhaps in areas with dark skies. The Geminid shower, peaking now, is the richer shower. At its peak, the Geminids may feature 120 meteors an hour, while the Perseids reaches 90 meteors an hour.
This year’s Geminid showers features dark, moonless skies. The young Moon does not even enter the picture on Wednesday night, and on Thursday it sets at 5:51 P.M.
The peak of the shower this year is at 2:00 P.M. on Wednesday afternoon, when we cannot watch. While not the best, that timing gives us two good nights to watch for Geminids, Wednesday night into Thursday morning and Thursday night into Friday morning.
The timing during the night is important. Early in the evening when the radiant – the point the meteors can be traced back toward – is low, fewer meteors are seen. Those that are visible, however, are generally slow moving, travel across a wide swath of sky, and bright offerings can be impressive. By 10:00 P.M. the radiant, in Gemini near Pollux, is about 40 degrees high and more meteors will be seen. The radiant is highest at 2:00 A.M., when it is around 76 degrees high in the south.
Before the peak, the best show will be Wednesday night after midnight, especially during the hours from around 2:00 A.M. until dawn on Thursday morning. More meteors are seen after midnight since we are on the front side of Earth moving through space. The first traces of sunlight will appear at 5:37 A.M. If you prefer evening hours, you should see some meteors after 10:00 P.M. Wednesday, and even some earlier Earth grazers if early hours appeal more.
After the peak, the best show is likely to be Thursday evening, perhaps during the later hours before midnight.
The prime requirements for enjoying a meteor shower are to have a good view of the sky and, in December, to be warm and comfortable. A reclining lawn chair is good for comfort. Dress in layers, more than you would wear for outdoor activities – its much easier to get chilled when you are inactive. A few blankets or a quilt can help. If you can, find a viewing spot away from city lights.
When the radiant is high, meteors can appear anywhere in the sky. Early in the evening, when the radiant is low in the northeast, looking high in the northeast is recommended.