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




The Sky for September 2010

By Faylene Roth


Sunrise and Sunset Times for
September 2010

1

6:48am

7:48pm

2

6:48am

7:47pm

3

6:49am

7:45pm

4

6:50am

7:44pm

5

6:51am

7:42pm

6

6:52am

7:40pm

7

6:53am

7:39pm

8

6:54am

7:37pm

9

6:55am

7:36pm

10

6:55am

7:34pm

11

6:56am

7:33pm

12

6:57am

7:31pm

13

6:58am

7:29pm

14

6:59am

7:28pm

15

7:00am

7:26pm

16

7:01am

7:25pm

17

7:02am

7:23pm

18

7:02am

7:21pm

19

7:03am

7:20pm

20

7:04am

7:18pm

21

7:05am

7:17pm

22

7:06am

7:15pm

23

7:07am

7:14pm

24

7:08am

7:12pm

25

7:09am

7:10pm

26

7:10am

7:09pm

27

7:10am

7:07pm

28

7:11am

7:06pm

29

7:12am

7:04pm

30

7:13am

7:02pm

MOON HAPPENINGS
September 2 – Last Quarter Moon rises at 12:06am
September 7 – New Moon occurs at 4:30am
September 16 – First Quarter Moon sets at 12:38am
September 23 – Full Moon rises at 7:04pm
(The time of moonrise and moonset assumes a flat horizon. Actual time may vary.)

AUTUMNAL EQUINOX
Summer relinquishes its hold on the northern hemisphere at 9:09pm, September 22. At that moment the sun’s apparent pathway through the sky crosses the equator and moves into the southern hemisphere. In celestial terms, the autumnal equinox marks the moment when the ecliptic crosses the celestial equator. (This point occurs in Virgo.) The tilt of the earth’s axis is perpendicular to the sun’s rays shining on the earth’s equator. Day and night are equal in length. That is not, however, what we observe, as noted in the Sunrise/Sunset table. Due to refraction, the sun is visible while still below the horizon. Our atmosphere causes light waves to bend around the curvature of the earth. It is not until September 25 that we perceive day and night to be of equal length; by then, the days will actually be shorter.

FINDING CONSTELLATIONS IN THE NIGHT SKY
The three brightest stars overhead form the Summer Triangle. It’s an asterism, not a constellation. Asterisms are identifiable shapes within or between constellations—like the Big Dipper (Plough or Wagon) in Ursa Major. The brightest of the stars, Vega, is in Lyra, the harp. Twenty degrees east of Vega is Deneb, which marks the tale of Cygnus, the swan.

(Use the distance guide at the end of the page to estimate distance across the sky.) The southernmost star of the Triangle is Altair, the heart of Aquila, the eagle. Altair is 35 degrees below both Vega and Deneb. Hercules can be found between Vega and Arcturus (brightest star in the eastern sky at the base of Bootes). Hercules is the large, but faint, trapezoid a bit more than ten degrees west of Vega. His legs and arms extend from each corner of the trapezoid. To its right is the Corona Borealis, shaped like the letter C.

Andromeda trails from the northeast corner of the Great Square of Pegasus, the flying horse. (Each side of the Great Square, another asterism, is about 15 degrees.) The two long, slightly bent lines that extend northward form the constellation Andromeda. The Andromeda Galaxy is visible nearby with the unaided eye. On the lower, slightly brighter line, count two stars away from the corner of Pegasus (not quite 15 degrees). Find the two stars that form a right angle upward from this point. The galaxy appears as a faint blur a bit more than five degrees along this line. A line from the star that joins the handle to the dipper in Ursa Major through Polaris (North Star) leads to Cassiopeia (Ethiopian queen).

Cassiopeia is the lazy W in the northeastern sky. Extend a line about 25 degrees from the lower of the two southernmost stars of the W to the crown of Cepheus (Ethiopian king).

With your thumb on Cassiopeia, the fingers of your outstretched hand should cover the square of Cepheus’s crown. Continue twenty-five degrees further to find the triangular head of Draco, the dragon. (Vega is ten degrees east. ) Follow its tail back towards Cepheus where it bends and wraps around Ursa Minor and down between it and Ursa Major.

METEOR ACTIVITY
Several minimal meteor showers occur this month, but none produce a reliable quantity of meteors. Sporadic meteor sightings, however, are common in September. These meteors originate from debris left over from interplanetary collisions within our solar system rather than comet debris. They may vary in size, color, and speed and may appear in any region of the sky. Large fireballs and exploding bolides are often associated with sporadic meteors. Meteorite landings are another possibility, since no meteorite has ever been traced to a comet-spawned meteor shower.

LOCAL STAR COUNT
Join Red Rock Astronomers at Old City Park on Sunday, September 12, at 8:30pm for a tour of the night sky and telescope viewing. Meet at the southwest corner of the park below the bandstand and the duck pond. Bring a chair or blanket for easy viewing. Sponsored by WabiSabi. All ages are welcome. For information call 259-4743 or 259-3313.

Note: Hold your hand at arm’s length to measure apparent distances in the sky. The width of the little finger approximates 1.5 degrees. Middle, ring, and little finger touching represent about 5 degrees. The width of a fist is about 10 degrees. The fist with the thumb extended at a right angle equals 15 degrees. The hand stretched from thumb to little finger approximates 20-25 degrees. The diameter of both the full moon and the sun spans only 0.5 degree. 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 - Watch for Jupiter as it rises in the early evening twilight in Pisces. It brightens this month as it approaches opposition on September 21. On that day it rises at 7:15pm on the eastern side of the earth as the sun sets at 7:17pm on the western side. This year’s opposition produces the brightest manifestation of Jupiter in its current 11.8 year orbit of the sun. (Magnitude -2.9)

Mars - Find a good view of the southwest horizon for a glimpse of the retreating red planet. Early in the month Mars is above Venus, both in Virgo. Mars continues its rapid orbital pace eastward and enters Libra during the last week of the month. (Magnitude +1.5)

Saturn - The bright yellow planet of the western sky settles lower towards the horizon each evening. It remains in Virgo. By mid-month it is too close to the sun to be visible. Saturn returns to view in late October’s morning sky. (Magnitude +0.4)

Uranus - Look for a blue-green point of light to the west of Jupiter. September 17-19 the two planets appear one degree apart. Around midnight they are due south, in Pisces. Uranus reaches its own opposition just five hours after the opposition of Jupiter on the night of September 21. (Magnitude +5.7)

Venus - Look for a line low on the southwestern horizon on September 1 formed by Venus and Spica (Virgo) about one degree apart, with Mars three degrees from Spica. On September 23 Venus peaks in brightness as it moves from Virgo to Libra. A telescope reveals that the planet is in its crescent phase. (Magnitude -4.5)

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
Aquila
Cygnus
Lyra



Northward
Cassiopeia
Cepheus
Draco
Ursa Major
Ursa Minor


Eastward
Aquarius
Pegasus
Perseus
Pisces

Southward
Capricornus
Sagittarius
Scorpius




Westward
Bootes
Corona Borealis
Hercules
Libra
Ophiucus

The lone star above the southern horizon is Fomalhaut---“mouth of the fish.”
This 1st magnitude star, part of a faint constellation called Pisces Austrinus,
passes directly over Argentina, South Africa, and Australia at -30 degrees South latitude.

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 night sky from astronomical twilight to midnight. As the night and the month progress, the constellations will shift toward the northwest.

 
 
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