SKYWATCH

December 1995

by Steve Stefanik

As we rapidly approach the winter solstice, which is due to occur on the 22nd of this month at 3:17 a.m. EST, the earth will be inclined at its greatest angle (23.5 degrees) away from the sun. The result is that the equator will be 23.5 degrees higher than the ecliptic (the apparent path of the sun across the sky) so that the resultant angle of the sun above the horizon will be considerably lower (and more southerly) in the sky. The obvious effect will be the noticeably shorter distance the sun will travel from the eastern to the western horizon which translates into less time the sun will be visible, considerably less, almost 16 hours less. The detriment is that fewer hours of light translates into less heat.

The good news is that it will become dark sooner which translates into earlier observing. As December begins, it will be dark enough by 5:00 p.m. to see the planet Saturn due south. Although dimmer (at magnitude +1.1) than it was this past summer, it is still one of the brightest objects amoung the dim stars in that region of the sky so you should be able to locate it fairly easily. If you have a telescope to view it through, the rings still appear to be edge-on. They will remain that way until February when the earth crosses their plane for the last time in this century and begin to "open up" once again to their more familiar appearance.

Meanwhile, after the sun sets in the west, the planets Mars, Jupiter, and Venus appear low on the southwestern horizon. Venus is easy to spot at a blinding -4.0 magnitude. Jupiter is a little tougher at magnitude -1.8 and lower and to the right of Venus. Mars is the most difficult of the three at magnitude +1.3, but you may be able to locate it with binoculars between the other two planets about 8 degrees above and to the left of Jupiter.

Mercury replaces Jupiter in the trio by the end of the month. As Juipter heads towards a conjunction with the sun, Mercury passes it on the evenings of the 7th and 8th on its return trip from around the sun. It will appear about 2 degrees lower and to the left of Mars on the evening of the 22nd on its way up to its maximun altitude of 13 degrees to the lower right of Venus by the end of the month.

By the time the last of these planets sets, and the sky is completely darkened, if you turn around 180 degrees and look to the east you should recognize the old familiar winter constellations of Orion and Gemini. Orion of course is the hunter, depicted by four bright stars at the corners and three bright blue-white stars evenly spaced apart in a straight row across his midsection and a cluster of three stars hanging from the left side of this "belt".

Gemini is to the left of Orion more to the northeast. Two bright white first magnitude stars, the so-called "twins" Castor and Pollux, depict the heads of the pair. Below them are several proportionately bright pairs of stars that demark their figures.