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This December begins with a full moon in the sky and ends with another full moon. While the first full moon is officially November 30, for all practical purposes the night sky will be saturated with practically full moon light the first days of December, virtually killing stargazing seriously. On December 30th we will have an official full moon that many Native American tribes called the “Cold Moon,” which shouldn’t be surprising.
Between these full moons there is a lot to do in the night celestial theater. The biggest event is the historic conjunction between Jupiter and Saturn. A conjunction occurs when two or more astronomical bodies appear to be close together in the sky from our view of Earth. We see many of them throughout the year. The conjunction. though. between Jupiter and Saturn is monumental. The last time these two planets were this close was when Galileo was still alive!
Since last summer, these two giant planets have been putting on a fantastic show. They have been faithfully side by side, with Jupiter the brighter of the two. They are getting even closer to each other in the night sky as they travel in their respective orbits around the sun. This month, they can easily be seen in the low southwestern sky towards the end of the evening twilight, which sets about an hour later. In early December, Jupiter and Saturn will be less than two degrees apart. It is about the width of two of your fingers held together at the length of an arm. Jupiter is in the lower right of Saturn. On December 21st, which coincides with the Winter Solstice, Jupiter and Saturn will be only a tenth of a degree apart! This is the time when these planets have been closest to each other in the sky since 1623. They will appear as a “double planet”. Consider the duo as the “Christmas star” of 2020. After the year they had this world, we deserve a celestial party like this! Just before the magnificent conjunction peaks, there will be a thin crescent moon near the planets on December 16th and 17th to really sweeten the view!
Another major event this December is the annual Geminid meteor shower, one of the best of the year. This will be an excellent year for the Geminids as there will be no moonlight in the sky at night. The Geminid meteor shower peaks on the night of December 13-14. I’ll have a lot more on the Geminids next week on Skywatch.
Even without all of December’s special events, this is a great month for stargazing. Although it is generally much colder (or colder), you have the longest nights of the year. In most locations. you can start stargazing well before 6 p, m. Mars continues to fade after its big October show, but it’s still the brightest star-shaped object in the southern evening sky. You may still be able to spot some of its surface features with a moderately sized telescope.
The great horse Pegasus is riding high in the southwestern sky not too far from Mars. In the northern high skies is Cassiopeia the queen, resembling a “W.” large, bright and almost upward. Ursa Major is still very low in the north, but as December continues, you will notice that it begins the evenings higher and higher in the northeast sky, standing diagonally on its handle. The Little Dipper hangs by its handle above the Big Dipper, with Polaris, the North Star, hovering at the end of the handle. Since Polaris shines directly above the North Pole of the Earth, it appears that all stars in the sky in the Northern Hemisphere revolve around Polaris once every 24 hours, including our sun. You are seeing the rotation of the Earth reflected in the sky.
Looking east, just after the evening twilight ends, you will be bombarded with all kinds of bright stars, and even more as the late evening arrives. You are witnessing the rise of the winter constellations, the best of the year in my opinion. Charioteer the chariot driver and Toro the bull lead the charge. Above Taurus is the best star cluster in the sky, known as the Pleiades and the Seven Little Sisters. This is a young group of stars, over 400 light-years away, that looks like a tiny Big Dipper. After 8pm, Orion the Hunter, the great centerpiece of the winter constellations, rises well above the eastern horizon. The three stars in a row equally spaced that make up the belt of the great hunter will surely jump on you.
Enjoy everything that’s happening in the celestial night theater this month. It’s more than worth it to regroup!
Mike Lynch is a retired amateur astronomer and meteorologist for WCCO Radio in Minneapolis / St. Paul. He is the author of “Stars: a Month by Month Tour of the Constellations”, published by Adventure Publications and available at bookstores and adventurepublications.net. Mike is available for private star parties. You can reach him at [email protected].
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