Our Friendly Skies - January 2010

December 29, 2009|By ROD MARTIN / Brish Planetarium and ANDY SMETZER / Tristate Astronomers

Visible evening planets

Jupiter is the bright evening planet low in the southwest.

Mars enters the evening sky as Jupiter sets.

Visible morning planets

Saturn rises before midnight and is high in the morning.

Mercury is visible in the east before sunrise early in the month.

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

Solar System

Mars is smaller than Earth, farther from the sun than Earth, but seems to be the most hospitable planet to explore. There has always been something special about the Red Planet. Science fiction authors have surmised about Martians. Its surface is rocky and desert like. It also seems like a place where life could have existed.

Mars's orbit is larger than the Earth's orbit, so their movements seem to be similar to two cars on a racetrack. The Earth is on the inside and catches up to and passes Mars on its outer lane path. Earth catches Mars about every 26 months. That is the best time to observe the Red Planet.


When Mars is directly opposite the sun in our sky, opposition occurs. Mars is visible almost all night and is closest to Earth, thereby providing our best views of the small planet. At opposition, the polar ice caps, plains and other features may be visible. It also is brightest.

Mars reaches opposition on Jan. 29. It brightens from about -1 to -1.3 magnitude. This isn't the best possible opposition, but this will provide the best observational opportunity until 2014. Watch Mars move backward or retrograde from Leo the Lion into Cancer the Crab.

The other evening planet is Jupiter. We have been following it for several months, but alas, all good things must come to an end. This month it is in the southwest, but sets earlier each night. By the end of January, Jupiter will be setting during late twilight. Check out the giant planet while you can. It is brighter than any star at -2 magnitude, but getting lower and lower.

Saturn now rises during the evening, but late enough that it is still best seen in the morning. Early in January, Saturn rises around 11:30 p.m., but by 9:30 p.m. late in the month. It is in Virgo and a little over halfway up in the sky when highest in the south. At slightly brighter than +1 magnitude, Saturn will brighten since we are now seeing its ring system open slightly to our view.

Mercury reaches inferior conjunction on Jan. 4. That is when it passes between Earth and the sun. It will emerge into our morning sky around midmonth and put on a fairly impressive appearance. Look for the bright "star" in the east about a half hour before sunrise the last couple weeks of January.

Venus reaches superior conjunction when it passes behind the sun on Jan. 11. It will not be visible this month.

Sun and moon

Since we have only recently passed the winter solstice, we still have more nighttime than daylight, but the nighttime is now beginning to shorten while daylight increases.

One of the strange things about astronomy is the seasonal shift. It would make sense that the reason that it is cold in the winter is because we are farther from the sun. That's not true. Our seasons are caused by the tilt of Earth on its axis and the annual voyage around the sun. A paradox is that we are actually closer to the sun in January than in July. We are colder because the sun's angle is lower.

On Jan. 1, the sun rises at 7:32 a.m. and, sets at 4:57 p.m., for 9 hours and 25 minutes of daylight. By Jan. 31, the sun rises at 7:20 a.m. and sets at 5:30 p.m. for 10 hours and 10 minutes of daylight.

The sun enters the astronomic boundaries of Capricorn from Sagittarius on Jan. 19.

The moon reaches last quarter on Jan. 7, new on Jan. 15, first quarter on Jan. 23, and full on Jan. 30.

There will be an annular solar eclipse on Jan. 15, but it will not be visible to us.

Brish Planetarium

The public program is "Bad Astronomy." The program will be presented on Tuesdays from Jan. 12 to Feb. 23 at 7 p.m.

"Bad Astronomy" tries to debunk myths and misconceptions about flying saucers, moon landings and more.

Programs are held Tuesday evenings at 7 p.m. when schools are in session, unless noted otherwise. If schools are closed all day or dismissed early due to inclement weather, that night's program is canceled.

Admission costs $3 for adults and $2 for children and students. Senior citizens with a WCPS gold card are admitted free.

Tristate Astronomers

The Tristate Astronomers meet monthly in the planetarium. For more information and schedules for the club, go to

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 The phone number is 301-766-2898.

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