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Our Friendly Skies - December 2009

November 30, 2009|By ROD MARTIN / Brish Planetarium and ANDY SMETZER / Tristate Astronomers

Visible evening planets

Jupiter is in the southwest after sunset.

Mercury is visible low in the southwest.

Mars rises before midnight.

Visible morning planets

Mars is high in the southwest.

Saturn rises shortly before the sun.

For more information about the visible evening planets and nighttime sky, download the planetarium's podcast "Skylights" from

Solar System

This month, the visible planets seem to be in transition. Some of the brightest ones are becoming harder to observe well, while others are not well placed for easy observation.

A surprise may be the elusive planet Mercury. It passed behind the sun last month and re-emerged late in November. Mercury will reach greatest elongation on Dec. 18. That is the best time to see it, but it should be visible all month. Look for a bright star in the western twilight glare.


Many people have never seen Mercury because of its proximity to the sun, it's never far from it. This month gives you a great chance to see it for yourself.

Jupiter is bright at -2.2 magnitude but is getting fainter as it approaches the sun. It is the brightest starlike object in the southwest after dark.

Jupiter helps us find the dimmest of the classical planets, namely Neptune, this month. The two giants are close to each other several days, but are within 0.6 degrees on Dec. 21. That is about the width of the full moon.

Neptune will be north of Jupiter. You should see Neptune with a good pair of binoculars; just remember that it will look like a dim star.

Mars rises around 11 p.m. early in December, but around 8 p.m. late. It is within the constellation Leo toward the right of the backwards question mark that resembles the head of the king of beasts. Mars is now brighter than any of the nearby stars except a couple below Orion. Mars can be identified by its reddish color.

Saturn rises around midnight and is high in the morning.

Venus has dropped too close to the sun to see well. Wait until 2010 to see it pop up into the evening sky.

Geminid Meteor Shower

One of the easiest meteor showers to observe is the Geminid Meteor Shower.

This is a convenient shower because it is one of the few that is visible before midnight. The meteors will seem to originate from the area of the Gemini Twins, which is visible most of the night. The peak activity is the night of Dec. 13/14. Expect many bright, medium speed meteors to cross the sky.

Sun and moon

Because of the earth's tilt, the sun has been climbing lower and lower in the sky since the beginning of summer in June. On Dec. 21, the sun bottoms out 23.5 degrees south of the equator. On Earth, the location is marked by the Tropic of Capricorn. This is the winter solstice, which is Dec. 21 at 12:47 p.m.

The bottoming out of the sun and its rising higher has been the origin for many "rebirth of the sun" celebrations throughout history. You can hear about some of these ideas at the planetarium on Tuesdays in December as well as at Discovery Station in downtown Hagerstown on Saturday, Dec. 19.

You will see more about these events below.

On Dec. 1, the sun rises at 7:12 a.m.. and sets at 4:47 p.m. for nine hours and 35 minutes of daylight. On the solstice, Dec. 21, the sun rises at 7:28 a.m. and sets at 4:50 p.m. for nine hours and 22 minutes of daylight. This is the shortest daylight of the year. By Dec. 31, the sun rises at 7:31 a.m. and sets at 4:56 p.m. for nine hours and 25 minutes of daylight.

The sun enters the astronomical boundaries of Sagittarius from Ophiuchus on Dec. 18.

The moon reaches full on Dec. 2, last quarter on Dec. 8, new on Dec. 16, first quarter on Dec. 24, and a second full moon on Dec. 31. The second full moon in the same calendar month is called the "Blue moon." So 2009 ends and 2010 begins with a big, bright, blue moon, even the color won't be blue.

Brish Planetarium and events

The public planetarium program is "'Tis the Season." The program examines many of the seasonal customs based on light as well as various winter holiday traditions including Yule, greenery, Santa and the Christmas star. The programs are held on Tuesday, Dec. 1, 8, 15 and 22 at 7 p.m.

Admission costs $3 for adults, $2 for children and students, and senior citizens with a WCPS Gold Card are free.

Rod Martin, resource teacher of the Brish Planetarium, will present the "Star of Bethlehem" at Discovery Station in Hagerstown during the afternoon of Dec. 19. This PowerPoint presentation highlights the night sky and ideas about the stars. Contact Discovery Station for more details.

The planetarium is at the central offices of Washington County Public Schools on Commonwealth Avenue off Frederick Street in Hagerstown.

The planetarium's Web site is  For more information about schedules and special events, go to

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