Our Friendly Skies - December 2012

November 30, 2012|By CHRIS KOPKO/William Brish Planetarium and ANDY SMETZER/Tristate Astronomers
  • The All-Sky Chart for December 2012
Tristate Astronomers

It’s December and soon winter will officially be here. This year, Dec. 21 marks the winter solstice, or the first day of winter. On this day we will have less daylight than on any other day of the year. This is because the sun traces its lowest path of the year through the daytime sky. This occurs because Earth revolves around the sun and is titled 23 1/2 degrees on its axis.

When the earth gets to the point in its orbit where the northern hemisphere (the half of the earth located above the equator) is tilted directly away from the sun, we have the first day of winter. However, at the same time that the northern hemisphere is tilted directly away from the sun, the southern hemisphere (the half of the earth located below the equator) is tilted directly toward the sun, resulting in the longest day of the year for them. This is their first day of summer or the summer solstice. The seasons in the opposite hemispheres are always opposite one another because of the tilt of the earth.

Now let’s talk about what we can see up in the night sky, starting with some of the bright stars that can be found early in the evening this month.

There are many bright stars found in the eastern sky in December. Start by looking toward the east where about half way between the horizon, where the land meets the sky, and the zenith, the point directly overhead at your location, you will find a very bright object in the sky. This object will look like a very bright star, but will in fact be Jupiter, by far the largest planet in our solar system.

Jupiter will shine very close to another bright object in the sky that will mark the top of one side of a “V” shaped constellation known as Taurus the Bull. Extend out from the tops of the “V” to the northeast to find the tips of the horns of the bull. Looking back to the west will bring you to the Pleiades, or the seven sisters, a small group of stars that mark the shoulder of the bull.

Now, look back to Jupiter and turn a little to the northeast to your left to see the bright star Capella. Capella is one of five main stars that make up the pentagon shaped constellation, Auriga.

Turn back to the east and look just a little above the horizon to see three stars in a row that make up the belt of Orion the Hunter. The bright red star above the belt to the north is called Betelgeuse and marks one of the shoulders of the hunter, while looking below the belt to the south you will find a bright blue star called Rigel, that marks the knee of the hunter.

For a more detailed tour of the night sky, check out Skylights, the monthly podcast tour of the night sky, It can be downloaded at


Evening Planets

MARS will glow orange in the western sky in December and will continue to set about two hours after sunset throughout the month, as it has for most of the fall. Mars will be fairly easy to spot a little over a half an hour after sunset at about magnitude 1.1.

JUPITER on the other hand will be shining brightly in the eastern sky as the sun sets and will be at opposition on Dec. 2, meaning it will be directly on the opposite side of the earth from the sun. Jupiter will be easy to spot in Taurus, as it will be much brighter than the surrounding stars and will shine at magnitude -2.8.

NEPTUNE & URANUS can both be observed after sunset, but cannot be seen with the unaided eye. Uranus can be found in Picses high in the southern sky, while Neptune will be in Aquarius closer to the southwestern horizon.

Morning Planets

VENUS, MERCURY and SATURN will begin the month lined up above the southeastern horizon with Saturn rising first, about three hours before sunrise, followed by Venus and then Mercury. As the month progresses, however, Venus and Mercury move to the east in relation to the background stars getting further away from golden Saturn.


On Dec. 1, sunrise is at 7:12 a.m. and sunset at 4:47 p.m., for 9 hours and 35 minutes of daylight. By Dec. 31, sunrise will happen at 7:32 a.m., with the sun setting at 4:56 p.m., for 9 hours and 24 minutes of daylight -  an 11-minute decrease from the beginning of the month.

On Dec. 15 the sun leaves Scorpius and enters the constellation Sagittarius. The change is caused by the earth’s revolution around the sun. The sun seems to line up with distant background stars from our viewpoint here on Earth, so the sky changes by seasons and months.

Third quarter moon is Dec. 6, new moon on Dec. 13, first quarter on Dec 20, and the moon will be full on Dec. 28.


The Geminid meteor shower takes place this December and is traditionally one of the best celestial shows of the year. There will be no moonlight during peak times for the Geminids this year on the night of Dec. 13 into the morning of Dec. 14, making it much easier to find a dark sky in which to watch the event. With dark skies you can expect to see somewhere in the neighborhood of 120 meteors per hour with this spectacular show!


The William Brish Planetarium will run programs open to the public on the first and third Tuesdays of the month at 7 p.m., unless otherwise noted. December shows will be held Dec. 4, Dec. 11 and Dec. 18. For more information, visit

The next meeting for the TriState Astronomers will be held at the William Brish Planetarium on Wednesday, Dec. 14, at 7:30 p.m.. All are welcome! For more information, visit

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