Tis the Season to be Under the Stars!
No matter what holidays you celebrate this time of year, there's much to celebrate in the night sky in December. Believe it or not, there's even a little Christmas tree in the night sky that I'll tell you about in a bit.
December's full moon is on the 27th. One of its nicknames is the Cold Moon, for good reason. Since the full moon isn't until late in the month, the best stargazing will be in early and mid-December, with little or no moonlight washing out the heavens. The timing of the darker skies this month couldn't be better for viewing December's meteor showers.
We have a major and a minor meteor shower this month. The biggie is one of the best of the year, the annual Geminid meteor shower. It peaks on the night of December 13-14th. The very to the Geminids will be from around midnight to the beginning of morning twilight. The best to see meteors in any meteor shower is after midnight. No moonlight means lovely dark skies for the Geminids this year, making catching the meteors, even the fainter ones, much easier. Lie back in a reclining lawn chair wrapped in blankets and roll your eyes around the sky. In the countryside, seeing well over 50 meteors an hour is possible. If it looks there's going to be cloudy skies on the night of the 13-14th, try looking two or three nights before or two to three nights after the peak. You may not see as many meteors, but it's better than being shut out entirely. The Geminid meteor shower is not only prolific, it's unique. Most meteor showers result from the Earth running into debris trails left behind by a comet. An asteroid, 3200 Phaethon, supplies the ammunition for the Geminids.
A little later in December, there will be a minor meteor shower. It's the Ursids, peaking the night of December 22-23. At best, it only produces 10 to 20 meteors an hour. It's still worth your while, though.
Around the same time as the Ursids is the winter solstice, the astronomical start of winter. This year, it's on December 21st. The sun shines directly over the Tropic of Capricorn on the winter solstice. It's the longest night of the year in the Northern Hemisphere and the shortest night in the Southern Hemisphere. From now until late next June, the sun's path among the backdrop of stars will slowly migrate northward, and the sun will appear higher and higher in the sky in the northern hemisphere, and days will get longer and longer. Speaking of the sun, mark your calendars for April 8th, the next total solar eclipse that'll cut a path across parts of North America and the United States!
Believe it or not, we can still see a few summer constellations in the early evening western sky despite it being December. Look for the "Summer Triangle" of stars: Vega, Altair, and Deneb, the brightest stars in their respective constellations, Lyra the Lyre, Aquila the Eagle, and Cygnus the Swan. Deneb is at least 1400 light-years away and marks the tail of Cygnus the Swan. Within the constellation Cygnus is the wonderful asterism, the Northern Cross. This time of year, the Northern Cross stands upright above the northwest horizon. I think everyone has heard of the famous Southern Cross constellation, seen in the Southern Hemisphere and southern portions of the Northern Hemisphere. The Southern Cross is brighter, but the Northern Cross is larger. Elsewhere in the December evening sky, the great horse Pegasus rides high in the south with Cassiopeia the Queen, resembling a bright "W," perched high in the north. Meanwhile, the Big Dipper hangs very low in the early evening northern sky, and depending on where you live, it may be partially below the horizon.
Among the constellations in the evening sky are the planets Jupiter and Saturn. Jupiter is the brighter of the two, shining like crazy in the eastern sky, and Saturn is in command in the lower southwest sky. On the 17th, the new crescent moon will be perched just to the lower left of Saturn. On December 21st, look for the waxing gibbous moon in tight conjunction with Jupiter, just to the right of the largest planet in our solar system. The next night, on the 22nd, the moon will be just to the upper left of the Jovian giant. Using even a small telescope, you should easily resolve Saturn's beautiful ring system, as well as the nightly show put on by Jupiter's four moons. They appear like little stars on either side of Jupiter's disk and continually change their positions as they orbit the enormous planet.
The later you stay up in the evening, the better you'll see the fabulous winter constellations. The best one is Orion the Hunter. Its calling card is the three bright stars in a row that make up his belt. Preceding Orion is the bright constellation Taurus the Bull, with the beautiful Pleiades star cluster. There's also Auriga, a constellation resembling a lopsided pentagon, with the bright star Capella marking one of the corners. Auriga is supposed to be a chariot driver turned goat farmer. Just north of Orion is the constellation Gemini the Twins, with the bright stars Castor and Pollux that mark the heads of the twins Castor and Pollux.
As promised, I want to tell you about the Christmas Tree Cluster, more formally known as NGC-2264. All you need to see the cluster is a pair of binoculars. It's high enough in the sky for decent viewing between 8 and 9 p.m. The best way to find it is to use the constellation Orion. On the upper left corner of Orion is Betelgeuse, a bright reddish star that marks the hunter's armpit. On the upper right corner of Orion is Bellatrix, not quite as bright as Betelgeuse. Draw a line from Bellatrix to Betelgeuse and continue that line about ten degrees to Betelgeuse's lower left. Ten degrees is about the width of your fist at arm's length. Scan that area with your binoculars or a telescope, and you should eventually find the Christmas Tree Cluster. Check out the Sky Guide app will help you pinpoint it.
Once you find the cluster, you'll see about twenty stars arranged in the shape of a Christmas tree, but its brightest star is actually at the tree's base. I know it will add to your holiday spirit!
Have a fun-filled and star-filled, most wonderful time of the year!
Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul, and is author of the book, “Stars, a Month by Month Tour of the Constellations” published by Adventure Publications. Available at bookstores and online at www.adventurepublications.net.
If you have any astronomical questions or want me to write about something you’re seeing in the night sky drop me a line at email@example.com