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SKY HAPPENINGS

Moab UT (at City Hall)
38O34’ N Latitude 109O33’ W Longitude
4048 ft - 1234 m

The Sky for December 2013
By Faylene Roth

 

Sunrise-Sunset
For December 2013

DATE

SUNRISE

SUNSET

1

7:17am

4:57pm

2

7:18am

4:57pm

3

7:19am

4:57pm

4

7:20am

4:57pm

5

7:21am

4:57pm

6

7:22am

4:57pm

7

7:23am

4:57pm

8

7:24am

4:57pm

9

7:24am

4:57pm

10

7:25am

4:57pm

11

7:26am

4:57pm

12

7:27am

4:57pm

13

7:27am

4:58pm

14

7:28am

4:58pm

15

7:29am

4:58pm

16

7:29am

4:59pm

17

7:30am

4:59pm

18

7:31am

4:59pm

19

7:31am

5:00pm

20

7:32am

5:00pm

21

7:32am

5:01pm

22

7:33am

5:01pm

23

7:33am

5:02pm

24

7:34am

5:02pm

25

7:34am

5:03pm

26

7:34am

5:04pm

27

7:35am

5:04pm

28

7:35am

5:05pm

29

7:35am

5:06pm

30

7:36am

5:06pm

31

7:36am

5:07pm

Imagine the flattened plane of our spiral-shaped Milky Way Galaxy. Position a dot to represent our solar system on one of the spiral arms about two-thirds the distance from the center. In winter our view of the Milky Way from Earth is through the middle of the plane of the galaxy but directed outward towards its edges. Trace its path across the sky—through Cygnus, Cepheus, Cassiopeia, Auriga, and farther on between Orion and Gemini and the two bright “dog” stars in Canis Major and Canis Minor. Then imagine the edge of our galaxy commingling with the dust, gases, and atoms of the Universe beyond.

DAYLENGTH
At the winter solstice the sun’s position on the ecliptic (apparent pathway across the sky) reaches its southernmost point for the year and the shortest day (9 hours 28 minutes) of the year occurs. The sun does not actually move southward. It is our perspective from the northern hemisphere that causes it to appear farther south. Remember that the earth is tilted in relation to the plane of the solar system by about 23.5 degrees. During our winter months, the earth is tilted away from the sun which means that the sun must rise over the hump of the equator before we see it. After appearing stationary for several days, the sun begins to rise higher in our sky—extending the period of visible daylight between sunrise and sunset.
winter Solstice

On December 21 at 10:11am MST the sun hovers directly overhead at 23.5° S latitude in parts of Namibia, Botswana, South Africa, Mozambique, Madagascar, Australia, Chile, Argentina, Paraguay, and Brazil—a line known as the Tropic of Capricorn on world maps. As these countries prepare for their summer season, the northern hemisphere fortifies for winter weather. The U.S. and Canada identifies the winter solstice as the beginning of the winter season. However, many European countries place the beginning of the winter season in early November and consider the solstice to be the mid-point of the season. Meteorologists designate December, January, and February as the winter season since the coldest average temperatures in the northern hemisphere occur during these months.

MOON HAPPENINGS
December 2 – New Moon occurs at 5:22pm.
December 9 – First Quarter Moon sets after midnight.
December 16 – Full Moon rises at 4:51pm and occurs at 2:28am on December 17
December25 – Last Quarter Moon soon after midnight.
(The time of moonrise and moonset assumes a flat horizon. Actual time may vary.)

METEOR EVENTS
The best meteor event of the year—with over 60 meteors per hour—remains a good watch even with a waxing full moon high in the sky. The Geminid Meteor Shower occurs December 7-17 with best viewing on the night of December 13/14. The radiant for this shower—Gemini—rises about 11:00pm, but meteor activity will increase as the radiant rises higher in the sky.

COMET WATCH
If Comet Ison has survived its pass by of the sun, then it may be bright enough that no instructions are necessary to find it. It should be visible at the beginning of December in the earliest stages of morning twilight (5:30am-6:30am). Red-tinted Arcturus (Boötes), red-hued Mars, blueish Spica (Virgo), and golden Saturn will adorn the eastern sky above Ison. Over the course of the month the comet moves northward. Trace its path from Saturn through Corona Borealis and on towards Polaris (North Star). By month’s end Ison brushes the lower bottom corner of the Little Dipper.

Other comets to watch this month are Comet Lovejoy and Comet Nevski. They may not reach naked-eye visibility, but could be visible with binoculars. Check the following websites for updates: universetoday.com and earthsky.org/space.

Note: Hold your hand at arm’s length to measure apparent distances in the sky. The width of the little finger approximates 1.5̊. Middle, ring, and little finger touching represent about 5̊. The width of a fist is about 10̊. The fist with the thumb extended at a right angle equals 15̊. The hand stretched from thumb to little finger approximates 20̊-25̊. The diameter of both the full moon and the sun spans only 0.5̊. Adjust for the size of your hand.

Primary Sources: USGS; U.S. Naval Observatory; Your Sky at http://www.fourmilab.ch/yoursky/
To find out when the space shuttle and International Space Station are visible from your location, go to: http://spaceflight.nasa.gov/realdata/sightings/index.html and click on Sighting Opportunities.

VISIBLE PLANETS

Jupiter - Jupiter outshines the Winter Circle of bright stars in the evening sky. The Circle includes the Gemini twins, Pollux and Castor. Clockwise, look for Capella (Auriga), Aldebaran (Taurus), Rigel (Orion), Sirius (Canis Major), and Procyon (Canis Minor). Betelgeuse (Orion) sits at the center of the Circle and Jupiter is located between Procyon and Pollux. Jupiter rises early evening and remains visible through the night. (Magnitude -2.4)

Mars– Look for Mars after midnight as it rises ESE in Virgo. Its red orb contrasts with blue-tinged Spica (Virgo) to its lower left. Mars remains visible through morning twilight about 45° above Saturn. (Magnitude +1.2 increasing to +0.9)
Mercury– Look for Mercury during the first two weeks of December while scanning the early morning sky for Comet Ison. Mercury (in Libra) appears very low on the horizon about 15° below Saturn and above Ison on December 1. During the next few days, Ison passes about 15° east of Mercury. (Magnitude -0.5)

Saturn– Morning twilight reveals four planets along the ecliptic: Mercury, Saturn, Mars, and Jupiter. On December 1, Saturn crests the eastern horizon (in Libra) as twilight begins to brighten the eastern sky. It then rises earlier each day, about 20° below Spica (Virgo). (Magnitude +1.2)

Venus– As Jupiter rises in the early evening, Venus sets in the western sky in Sagittarius. It is approaching its transit across the face of the sun in early January 2014. On December 6 Venus reaches its maximum brightness even though only 26% of its face is illuminated by the nearby sun. By the end of December it will be absorbed in the sun’s glare until it returns to view in late January. (Magnitude -4.9)

Note: Apparent magnitude values range from -4 to +6 for most planets and visible stars. The lower the value the brighter the object. A decrease of 1.0 magnitude is 2.5 times brighter.

MAJOR CONSTELLATIONS this MONTH

Overhead
Andromeda
Aries
Auriga
Perseus
Pegasus
Pisces

Northward
Cassiopeia
Cepheus
Ursa Major
Ursa Minor

Eastward
Canis Minor
Gemini
Orion
Taurus


Southward
Aquarius
Capricornus
Cetus

Westward
Cygnus
Lyra

Hold the star chart high above your head and match the compass directions to the direction you are facing. Adjust the star chart by orienting Ursa Major (Big Dipper) to match its position in the sky.

The star chart approximates the sky from astronomical twilight to midnight. As the night and month progresses, the constellations shift toward the northwest. The celestial equator is measured in hours (h). The ecliptic is measured in degrees.

Sky Map for Moab Feb 2013
 
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