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SKY HAPPENINGS

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

The Sky for January 2015
By Faylene Roth

 

Sunrise-Sunset
for january

(The time of sunrise and sunset assumes a flat horizon. Actual time may vary depending upon the landscape.)

DATE

SUNRISE

SUNSET

1

7:36am

5:08pm

2

7:36am

5:09pm

3

7:36am

5:09pm

4

7:36am

5:10pm

5

7:36am

5:11pm

6

7:36am

5:12pm

7

7:36am

5:13pm

8

7:36am

5:14pm

9

7:36am

5:15pm

10

7:36am

5:16pm

11

7:36am

5:17pm

12

7:35am

5:18pm

13

7:35am

5:19pm

14

7:35am

5:20pm

15

7:34am

5:21pm

16

7:34am

5:22pm

17

7:34am

5:23pm

18

7:33am

5:24pm

19

7:33am

5:25pm

20

7:32am

5:26pm

21

7:32am

5:28pm

22

7:31am

5:29pm

23

7:31am

5:30pm

24

7:30am

5:31pm

25

7:29am

5:32pm

26

7:29am

5:33pm

27

7:28am

5:34pm

28

7:27am

5:36pm

29

7:26am

5:37pm

30

7:26am

5:38pm

31

7:25am

5:39pm

Enjoy the holiday color of winter skies. Aldebaran (Taurus) and Betelgeuse (Orion) glow red, Pollux (Gemini) and Capella (Auriga) shine yellow. Castor (Gemini) and Procyon (Canis Minor) glimmer white. Rigel (Orion), Sirius (Canis Major), the Pleiades, and Regulus (Leo) twinkle blue.

Twilight extends the period of daylight in three stages at each end of the day. Morning twilight begins with astronomical twilight—about 1-1/2 hours (nearly 2 during summer months) before sunrise—as the eastern horizon brightens. Nautical twilight continues—as the overhead sky turns blue and color returns to the surrounding landscape—for another 30-40 minutes. The final stage—civil twilight—provides adequate light for most outdoor activities for the half hour before the sun crests the horizon. The opposite progression occurs after sunset.

DAYLENGTH
The length of daylight has increased by only a few minutes since the winter solstice. By midmonth we make up for lost time with an increase of about two minutes each day. At month’s end the period of daylight will be 47 minutes longer than it was on the solstice. Two factors are working against a quicker increase in daylength. One factor is solar time. It rarely coincides with clock time. Solar time is measured from one solar noon (sun at zenith) to the next. In a perfect circle, that would be one earth rotation. However, the earth speeds up as it approaches perihelion (see below). That means, after one rotation, it will have moved farther along in its orbit which leaves the sun farther east of the noon meridian. In January solar noon occurs about one-half second later than clock time which delays the time of sunset as well as the time of the next sunrise. As the earth’s speed slows later in its orbit, this nonalignment will correct itself and even overcorrect. It is called the equation of time. Another factor is declination (angle). Earlier sunrises will not occur until after January 10 when the sun’s declination raises enough to overcome the effect of perihelion.

PERIHELION
It is encouraging to know—as we wait for longer periods of daylight to become apparent—that the winter season in the northern hemisphere is five days shorter than its summer season. The reason relates to the Earth’s elliptical orbit. An ellipse—unlike a circle—has two foci, both offset from the center. The sun occupies one of these focal points. As the Earth orbits the sun it passes a near point—perihelion—and a far point—aphelion—six months later. This year Earth reaches perihelion at midnight on the night of January 3/4. Since the Earth speeds up at perihelion, it “races” through the winter season (summer, of course, in the southern hemisphere is shorter than its winter season). This year a full moon is only ten hours away from perihelion, so coastal tides will be higher than usual.


MOON HAPPENINGS
January 4– Bright skies all night after the full moon (at 5:27am) rises at 5:35pm.
January 13– Dark evening skies until after midnight when the waning last quarter moon rises.
January 20– Dark sky period for several days before and after the new moon at 6:36pm.
January 26– Bright evening skies until after midnight when the waxing first quarter moon sets.
(The moon rises later each day—as little as 30 minutes to as much as one hour. Time of moonrise and moonset may also be delayed in mountainous terrain.)

VISIBLE PLANETS

Jupiter – Follow Jupiter across the sky throughout the night. It rises about one hour after astronomical twilight on January 1. By the end of the month it appears at the end of civil twilight. (Magnitude -2.5).

Mars – Track this small red orb in the southwestern sky for about an hour as it sets at the end of astronomical twilight. (Magnitude +1.1).

Saturn – Look for Saturn in the pre-dawn sky. It rises shortly before astronomical twilight lightens the eastern horizon. (Magnitude +1.4) same

Venus – As the month progresses Venus will dominate the western horizon for more than an hour after civil twilight. (Magnitude -3.8)

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.

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.

MAJOR CONSTELLATIONS this MONTH


Overhead
Ursa Minor
Auriga
Gemini
Canis Minor
Taurus
Orion
Canis Major

Eastward
Ursa Major
Leo

Westward
Cepheus
Cassiopeia
Perseus
Andromeda
Pegasus
Aries
Pisces
Cetus


MAJOR METEOR EVENTS
Shower
Peak
(December)
Range
(December)
Constellation Radiant
Rate
(/hr)
Details
Conditions
Quadrantids
3/4
1-5
Boötes
40
After midnight-fireballs possible
Waxing full moon
Best time to view any meteor event is between midnight and morning twilight when the radiant is overhead. Trace the path of any meteor backwards through the sky to reach its radiant--the region of the sky from which meteors appear to originate.

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

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.

 
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