DECEMBER  2009

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694    DECEMBER 6, 2009:   Blazing Geminids to Light Yule Sky

Sunday evening into Monday morning, December 13/14, is the big night for viewing Geminid meteors. Unlike last year when the moon was full and near to the area where the Geminids were radiating, this year’s sky features an unobtrusive slivery moon. If you successfully bundle up against the cold, expect to see as many as 50 meteors per hour after midnight from suburban locations and rates as high as 125 shooting stars per hour from rural environs. Geminid meteors will begin to fly as early as 7 p.m. once the radiant, the area near the bright star Castor where the meteors are diverging, breaks the horizon. If you are going to observe before 10 p.m., face east and look overhead which is usually the darkest part of the heavens. Meteors will appear to fan away from the eastern horizon, but rates will be substantially reduced. Downward streaking Geminids will be missed altogether. Rates are further reduced before midnight because our location on the Earth puts us in a similar position to the back windshield of a car moving through a rain shower. Many more raindrops will strike the front windshield as the car plows ahead than hit the back window. After midnight, Earth rotates us into the driver’s seat and rates increase substantially. After midnight, Gemini will also be high in the east and will continue to get better positioned, allowing meteors to be viewed from all directions around the radiant. An online map is included with the web version of this article. By 2 a.m. the radiant is within 10 degrees of the zenith for mid-latitude observers. Flip your bedroll around so that it points to the west as Gemini heads into this area of the sky. It is from 2 a.m. until dawn that meteors should be popping at their highest rates, and the true greatness of this meteor event can be ascertained. Much success if you can brave the cold!

Geminid meteors will appear to radiate from a region of the sky near the bright star Castor. Look for orangey Mars, near the head of Leo the Lion. Up to 140 meteors per hour are predicted in the darkest rural areas. This map shows the sky at midnight on the morning of December 13-14, 2009. Map created by Gary A. Becker using Software Bisque's, The Sky software...

695    DECEMBER 13, 2009:   Eclectic Grouping After Sundown

As we head towards the winter solstice on December 21, an eclectic grouping of planets is gathering in the southwestern sky right after sundown. The assortment includes Jupiter, which is bright and easy to recognize; Mercury, which can be at times elusive; and Neptune, which will require a spotting scope or telescope to see. Jupiter has been no stranger to the heavens during the last three months. Since the beginning of September, it has sojourned from the southeast to its current location in the southwest. Mercury begins poking its head above the southwestern horizon this week, but reaches its greatest angular separation from the sun on the 18th. A flat, unobstructed southwestern horizon is mandatory. Binoculars will also prove helpful for the initial find. Start observing 15-20 minutes after sundown while scanning along the SW horizon. Then raise your binoculars about a half of field of view and repeat the scan until the sweep is one full field above the SW. The bright, starlike object which becomes visible very near to the SW horizon will be Mercury. Once Mercury’s location is confirmed, try seeing it with the unaided eye. For Neptune, December 19 will be the best day, but here you’ll need a small telescope. Simply point the scope with its lowest magnification eyepiece towards Jupiter during the early evening hours of December 18-23, and Neptune will be in the same field of view. Use the two locator maps found with the online version of this article. The Jupiter-Neptune map shows the scene as it will appear at 40 power. Telescopes most often invert and mirror the image so it may be advisable to copy the picture into a paint program, then adjust it to match what will be seen through your particular scope. Watch as the slivery moon marches past these three planets from December 18 through the solstice on the 21st.

Seeing this eclectic grouping of planets requires you to be at your observing location no later than 30 minutes after sundown. Find Mercury first, since it will be low to the horizon and setting by 5:50 p.m. Jupiter, the brightest object in the early evening sky will be a no-brainer, but you’ll have to wait until darkness before Neptune becomes visible. Read the article above. Map created by Gary A. Becker using Software Bisque's, The Sky software...

To view Neptune wait at least an hour after sundown and simply find Jupiter. The orientation of Jupiter’s moon is for a normal terrestrial view. Up, down, right, and left have not been interchanged. The numbers associated with the stars indicates their brightness. The more positive the number becomes, the fainter the star. Map created by Gary A. Becker using Software Bisque's, The Sky software...

696    DECEMBER 20, 2009:   Solstice Happiness

It’s cold outside, and yet I am celebrating! The Lehigh Valley (Eastern, PA) has already experienced its first late start of the school term due to ice and snow, and now the great sun turnaround, the winter solstice, is almost upon us. That is the day when the sun bottoms, rising farthest to the south of east and setting farthest to the south of west. At noon the sun reaches its lowest high point for the year. The solstice happens on December 21 at 12:47 p.m. EST. At that moment, the sun will be shining directly over the Tropic of Capricorn, 23-1/2 degrees south of the equator, marking this position as the southern limit of the vertical sun. It makes perfect sense for mid-northern hemispheric locations to witness the sun as low as it can go in the southern sky. But what is there to celebrate with winter fully upon us? The word “solstice” is Latin for “sun standstill,” a condition produced by the Earth’s axial tilt which causes the sun’s altitude to vary by 47 degrees each year. Ever since the summer solstice, last June 21, the sun’s noontime position has been lowering and the effects of less direct sunlight and a shorter period of daylight time have been contributing to a decrease in solar energy that is presently at its minimum. The sun is now at its standstill or solstice position, with Sol’s southward motion halted in the sky. For a day, the sun will pause before commencing its northward journey which will begin the process of lengthening the day and causing the sun to shine down upon us from a higher position, increasing the amount of energy received, and warming the world around us. Please understand that it will be a long process. We still have January, February, and March to “plow” through. But the promise of lazy, restorative, summer days spent in the mountains or on a warm, sunny beach, is already being written in the heavens. Happy winter solstice!

697    DECEMBER 27, 2009:   Under the Light of a Blue Moon

“Blue Moon, you saw me standing alone, without a dream in my heart, without a love of my own.” Although the lyrics of this song by Lorenz Hart have a happy ending, a blue moon has always had a weighty and sad meaning in romantic poetry and prose. Astronomically, a blue moon has always meant the second full moon occurring within the space of one month, or so I thought. When I wanted to write an article about blue moons just over a decade ago, I realized that I had never seen the term defined in print. Wanting to satisfy my curiosity, I went to the lunar section of my astronomical library and picked out a general text and thumbed through the index. There was no reference to a blue moon. Wondering about what I had been teaching my astronomy pupils over the past 25 years, I grabbed the book next to it. There was no blue moon reference. Seventy books later, I came up with only a few words about a moon that had actually appeared blue after a great forest fire in Canada. There was not a single word about a blue moon being the second full moon in a month. I panicked and was truly blue like the song. Oddly enough several weeks later, I discovered that the astronomical term for a “Blue Moon” had originated in the 1937 edition of the “Maine Farmers’ Almanac.” That book had given seasonal names to the full moons, of which normally there are 12 each year. Every two to three years, there are 13. To keep the naming cycle intact with the seasons, the third full moon in a season which contained four full moons was designated the blue moon. This realigned the lunar names with the calendar, as a sort of a leap moon. Another error in the March 1946 issue of “Sky and Telescope,” magazine gave us the blue moon as it is used today. The term never became popular until recently. A blue moon occurs on New Year’s Eve. Drive safely under its reflected sunlight.