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Skywatch for the week of December 20, 2021

Skywatch 12-20-2021.mp3


Winter begins in the earth’s northern hemisphere tomorrow, December 21st, at 3:59 pm, Eastern Standard Time. It's at this exact moment that the sun's rays fall most directly on the Tropic of Capricorn, twenty-three and a half degrees below the equator, where summer is beginning. For us in the northern hemisphere, today marks the shortest period of daylight, and also the longest night of the year. A few days before the Solstice, ancient Romans celebrated the Saturnalia, a festive time when gifts were exchanged, homes and streets were decorated, and everybody was in a happy party mood. As our winter season begins, we will be treated to a small meteor shower called the Ursids. Best views will be from about 9 pm until the waning gibbous moon rises in late evening. Grab a reclining lounge chair, dress warmly, get away from bright streetlights and face east, and hope for clear, dark skies.

Skywatch 12-21-2021.mp3


There’s an archaeological site in Ireland called Newgrange, but there isn’t anything new about it – in fact, it’s literally as old as the hills, being a hill itself. Five thousand years ago, a great many people went to a lot of trouble to build this giant earth mound, over an acre across, and surrounding it they set up great stones, etched with intricate swirls and other megalithic designs. Ancient tomb, ancient temple, Newgrange probably served both these functions. And like the Great Pyramid of Khufu or the Giant’s Dance known as Stonehenge in England, Newgrange is astronomically aligned. For a few days before and after the winter solstice - the beginning of winter - sunlight travels through a roof box or window over the main doorway. The shaft of sunlight travels all the way down a long, narrow corridor, until it lights up a small chamber at the center of the mound. It happened long ago, and it happens now.

Skywatch 12-22-2021.mp3

Wed Dec 22, 2021 ORION’S RETURN

An old friend has returned to our sky - the ancient constellation Orion the Hunter. You'll recognize him as he rises out of the east around 8 o’clock tonight: three bright stars close together in a row form the hunter's belt. In Robert Frost's "The Star Splitter," the poet begins by saying, "You know Orion always comes up sideways. Throwing a leg up over our fence of mountains, And rising on his hands, he looks in on me Busy outdoors by lantern-light." Orion does come up sideways, first his left shoulder, the star Bellatrix, and the hunter's knee, the blue-white star Rigel; then the belt stars come up in a line, followed by Orion's right shoulder, the well-known star Betelgeuse, and finally his right leg, the star Saiph. When I was young, I saw Orion, looking just as he does now, as did my grandparents, and their grandparents, and so on back for thousands of years.

Skywatch 12-23-2021.mp3


In 1301, the artist Giotto di Bondone saw a comet. It was bright and glorious, but it had no name; centuries later it would be called Halley’s comet, in honor of Edmond Halley, who calculated its regular return every 76 years. In 1305, Giotto painted a fresco called, “the Adoration of the Magi,” which can still be viewed in the Arena Chapel in Padua, Italy. Above the Creche, Giotto painted Halley’s comet, portraying it as the nativity star. Could the comet have been the star? Because astronomy, like other sciences, is predictive in nature, we can use it to figure out not only when Halley’s Comet will return (the year 2061,) but also at what times in the past the comet was visible in our skies. Based on this, we know that Halley’s Comet appeared in the year 12 BC, which was far too early for it to be considered as the Nativity Star. We will need to continue our search.

Skywatch 12-24-2021.mp3

Fri Dec 24, 2021 THE MAGI

Who were the Wise Men, the Magi? Our best guess is that they were Zoroastrian astrologer-priests of Babylonia. Two thousand years ago, from September 3 BC through May 2 BC, the Magi may have witnessed a triple conjunction, three separate passings of the planet Jupiter and the star Regulus, a significant sky event for them. Jupiter appears as a bright star that wanders against the background of constellations, caused by the combined motions of Jupiter and the earth as they orbit the sun. Regulus, in the constellation Leo the Lion, was the signal star of the Babylonian king. Jupiter’s appearance near Regulus may have set the Magi on their course toward Bethlehem to seek out a new king. Tonight, Jupiter is a bright star-like object well up in the southern sky at sunset. But there’s an even brighter star in the southwest – it is the planet Venus.