by William J. Bechaver
The winter nights are crisp and cold, and around here, primarily dry, lending themselves perfectly to dark, clear, steady skies ideal for astronomy, star gazing, and meteor watching.
Mars is still prominent in the sky as the Sun sets, and remains the only dominant planet left to us in the evening sky. But even it is fading into the distance.
The Moon is a fine, beautiful crescent in the evening sky this week, perfect for viewing. On especially clear nights, go out and see if you can view the dark side of the Moon. The nights being so clear, it is common to view the beautiful crescent, and the amazing dark shaded side of the Moon, lost in the shadow. The light illuminating that dark portion of the Moon is actually from Earth. Just as the full Moon brightens the night here on Earth, so too does the Earth brighten the sky during the night on the Moon. It is the reflected light from the full Earth that brightens the dark side of the Moon, allowing us to see the outline of the full lunar orb on clear, dark nights.
This week, the Moon will be progressing on toward the first-quarter phase, and on the night of Thursday 13 December, it will set about an hour before midnight. This is fortuitous for us here on Earth, for this week, the amazing Geminid Meteor Shower peaks on that very same night.
The Geminid Meteor Shower is one of the most plentiful and prolific meteor showers of the year. And this year, with the Moon setting in the late evening, the night will be dominated by the amazing meteor display.
Further, the constellation Gemini is rising high in the sky by the time the Moon sets, and will be practically directly overhead by the time the sky grows dark.
The meteors generally originate in the sky near the constellation Gemini, hence the name of the shower. With the radiant of the shower almost directly overhead, the entire sky will be involved in meteor activity.
So, after the Moon sets on Thursday night, go out and look in any direction. With Gemini high overhead, the best and easiest place to gaze is about forty-five degrees above the horizon, or half way between the horizon and the point directly overhead. The meteors in this region will have long, glowing trails across the sky, and promise to be plentiful.
A meteor shower occurs when a comet passes through the inner regions of the solar system. As it approaches the Sun, the outer surface of the comet heats up, and leaves a trail of icy particles in space. Later, when Earth in its orbit, passes through the debris field of icy particles, they impact on the upper surface of our atmosphere, burning up as they enter. As they do, they streak across our skies in quick and flaming glory, burning up for us on Earth, far below, to witness.
The Geminid meteor shower is caused by a very dense field of icy particles, so the number of impacts are high. And with the Moon out of our sky at the peak of activity, even more meteors will be visible as they impact.
This year, with the ideal circumstances, you should be able to see about 120 meteors an hour, looking in almost any direction, in any region of the dark sky. That’s an average of two every minute!
But remember, meteor impacts are irregular, and an hourly average can be misleading. You may see several meteors in one minute, then wait several more minutes before seeing another. Also, you may be looking north, when there are two in the southern sky, so you must be persistent and diligent.
Bundle up, and plan on spending at least ten minutes outside, a couple of times during the night. Let your eyes adequately adjust to the dark sky conditions. Try to be where there are no lights, or light interference, like streets and headlights.
Also, the debris field for the Geminids is extremely large, so the amazing display will continue for several days throughout the week. But, each night, the Moon will set about fifty minutes later than the previous night, cutting into your extended viewing time.
Magnificent Venus will rise at about three thirty, lending an additional viewing opportunity in the early morning sky. The magnificent jewel is shining brightest right now, and is a beautiful sight to behold in the dark eastern sky, an astronomical bonus gift this holiday season.
The Sun doesn’t begin to significantly lighten the sky until about six thirty, so between midnight and about six, you have significant viewing time to catch one of the most spectacular meteor showers of the year, and view more than just a few amazing Geminid Meteors!
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• · William J. Bechaver is the director of SPACE • Spanish Peaks Amateur Cosmos Enthusiasts, the premier Astronomical Society for Southern Colorado and Northern New Mexico.