Night Skies December 2, 2004
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The Night Skies of December, 2004Jupiter Occultation and Geminid Meteors Dominate December Skiesby Leo Enright
With our sunsets now occurring in the very early evening, the long nights of December give us extra time to enjoy the beautiful, star-studded winter sky. On the first day of the month, sunset is at about 4:25 p.m. EST, and it is only a few seconds, NOT minutes, earlier each evening until the earliest sunset of the year which is at about 4:24 p.m. on December 10th. Then sunsets are only a few seconds later each evening until the end of the month when sunset is at 4:33 p.m.. Meanwhile, in the mornings, sunrises are occurring a little later each morning from 7:25 a.m. on December 1st to 7:47 a.m. on December 31st. The latest sunrise of the year in this area does not occur until January 3rd. [Most people do not know that the date of latest sunrise in over 3 weeks later than the date of earliest sunset.] For those who watch where along the horizon the sun rises and sets, you can see that its most southerly positions (for rising in the southeast and setting in the southwest) both occur on December 21st, the date we call the Solstice, which means the sun standing still. Since late June the suns rising and setting positions on the horizon have moved southward, day by day, until this date; they now stop that movement and begin to move northward.
Just as, from our latitude, the sun appears to be weaker and farther south in December than in any month of the year, so the December Full Moon, always opposite the sun, appears to be higher and more northerly in the sky than at any time in the year. The Full Moon on the nights of December 26th and 27th is the most northerly Full Moon of the whole year. Weather permitting, on those two evenings just after Christmas, the moon may be seen rising, not in the east, but in the northeast, and it appears almost straight overhead by midnight, and when it sets early the following morning, it will be not in the west, but in the northwest.
This is the month to enjoy winters favourite star patterns brilliantly gleaming in the southern sky, the time when there are more bright stars to be seen than at any other season. Foremost of the easily recognized constellations is Orion the Hunter marching across the sky followed by his faithful dogs, Canis Major and Canis Minor. The first canine has the star Sirius, brightest star in the whole sky, to mark his eye, and the second one has the star Procyon, the sixth brightest star, to mark its location. Orion himself has very bright stars to mark his shoulders, knees, shield, sword and club, some of them almost as bright as the dog stars, and three distinctive stars in a row form Orions belt. This great hunter has moved up into the southeastern sky by 8:00 p.m., and by 10:00 p.m., his dogs are easily seen up there beside him. At this time of year, try to notice also the huge stellar trio, called The Summer Triangle, now much lower in the northwestern evening sky, and the bright stars forming Cygnus the Swan, or Northern Cross, standing above the northwestern horizon.
Of the five bright planets, all can be easily seen this month, but the eastern morning sky is the place to view most of them. Saturn is the first of the naked-eye planets to be seen in the evening, visible after 8:00 p.m. when it has risen in the east and is easily found below Castor and Pollux, brightest stars in the constellation Gemini. It is brighter than both of them. Very careful observers will be able to notice its slight movement over the course of the month in relation to the background stars. After 2:30 a.m. Jupiter, much brighter than Saturn, is easily seen in the east. It is one of the two planets that dominate the eastern sky until almost the time of sunrise. The other one is brilliant Venus which rises about 5:30 a.m. and is so bright that careful observers can actually follow it even past the time of sunrise. Reddish Mars, much fainter than Venus, is found slightly below Venus before December 5th, right beside Venus on the 5th and a little further above Venus each morning after the 5th. For those with a good view of the southeastern horizon during the last ten days of December, Mercury may be easily seen in that direction from about 6:00 a.m. until it fades into the morning twilight. Anyone who has never seen this seldom viewed planet should note that it is extremely easy to find between December 20th and January 10th, when it is very close to brilliant Venus, just to the left of that planet. They appear particularly close between Dec. 27th and 31st, and on the morning of the 29th their apparent separation is about the width of your little fingernail held at arms length.
As the moon moves past the planets this month there are several interesting sights, but the most watched one of all will be the moon passing Jupiter in the very early morning hours of Dec. 7th. In fact, the moon moves in front of Jupiter hiding it for over an hour in an event called an occultation. Begin watching at 3:00 a.m. and notice the moon, minute by minute, moving closer and closer to Jupiter. Use binoculars or small telescope, if you have them. At about 3:57 a.m. Jupiter will start to disappear behind the moon. Good binoculars or a small telescope will show that it takes over a minute for the whole planet to disappear, and perhaps about five minutes for all of Jupiters moons to disappear. As the moon moves on, the reappearance of Jupiter on the dark side of the moon will be equally spectacular! Watch for it at 5:02 a.m., and within a minute or so, Jupiter should start to emerge. Again it takes over a minute for the planet to appear completely and, if a telescope is used, several minutes for Jupiters four bright moon to emerge. Prepare for the event on the evening of December 6th. Set the alarm for 3:00 a.m. Later in the month, the moon passes the other planets. On the mornings of Dec. 8th and Dec. 9th, there are very beautiful 6:00 a.m. views of the crescent moon just above Mars and Venus, and the next morning, Dec. 10th, it is just below those two planets. Try not to miss them. On the three nights after the Christmas Full Moon, watch it glide through the constellation Gemini and past the planet Saturn (Dec. 26th, 27th, and 28th.) On the night of the 27th, it is between the star Pollux and the planet Saturn.
Meteor observers are particularly excited about the prospects of seeing a good number of meteors (commonly called shooting stars) at the peak of the Geminid Meteor Shower this year, a shower that has, in recent years, been sometimes as good as, or better than, the famous Perseid Shower of mid-August. Although this shower produces bright meteors from December 7th to December 17th, the peak of activity is during the night of December 13th-14th, particularly between 10 p.m. and 5:00 a.m. These meteors appear to come from the constellation Gemini, are frequently very bright, often with a yellowish trail as they burn up in the upper atmosphere, and they are much slower than the Leonid Shower meteors of mid-November. (Geminid particles strike the upper atmosphere at 35 kilometres per second, those of the Leonids at 71 km/sec.) Record the number you see in segments of one hour. If possible, observe over a few nights both before and after the peak night. Use a reclining lawn chair, dress properly to stay warm, and face in southeastern or northeastern direction.
More information about observing the night sky is to be found in the book The Beginners Observing Guide which is now available at Sharbot Lake Pharmacy. It is for young and old and could be a good Christmas gift suggestion. I wish all readers a very safe and merry Christmas holiday.
