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NIGHT SKY HAPPENINGS

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

The Sky for May 2017
By Faylene Roth

 

Sunrise-Sunset
for May

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

DATE

SUNRISE

SUNSET

1

6:21am

8:10pm

2

6:19am

8:11pm

3

6:18am

8:12pm

4

6:17am

8:13pm

5

6:16am

8:14pm

6

6:15am

8:15pm

7

6:14am

8:16pm

8

6:13am

8:17pm

9

6:12am

8:19pm

10

6:11am

8:19pm

11

6:10am

8:20pm

12

6:09am

8:21pm

13

6:08am

8:22pm

14

6:07am

8:23pm

15

6:06am

8:23pm

16

6:05am

8:24pm

17

6:05am

8:25pm

18

6:04am

8:26pm

19

6:03am

8:27pm

20

6:02am

8:28pm

21

6:02am

8:29pm

22

6:01am

8:29pm

23

6:00am

8:30pm

24

6:00am

8:31pm

25

5:59am

8:32pm

26

5:58am

8:33pm

27

5:58am

8:33pm

28

5:57am

8:34pm

29

5:57am

8:35pm

30

5:56am

8:36pm

31

5:56am

8:36pm

The Milky Way is absent from May evening skies. It lies below the northern horizon until after midnight when the long arm that stretches towards the galaxy center sweeps into view along the eastern horizon. A long isosceles triangle formed by bright 0-magnitude star Arcturus (Boötes) and 1st magnitude stars Spica (Virgo) and Regulus (Leo) still dominates the overhead sky. Use the Big Dipper—an asterism in Ursa Major—to identify them. Follow the handle of the Dipper outward in a 30 ̊ arc to Arcturus. Continue the arc and spike down about 35 ̊ to Spica. Follow the handle back to the cup of the Dipper, then use the two stars of the cup that touch the handle to trace a 45 ̊ arc southward to Regulus. Jupiter sits on the ecliptic about 15 ̊ west of Spica and about 45 ̊ east of Regulus. C-shaped Corona Borealis and the trapezoidal core of Hercules appear in the northeastern sky between Arcturus and 0-magnitude Vega (Lyra). The four faint stars of Libra sneak into the southern sky behind Virgo—sandwiched between Spica and the head of Scorpio. It is a good time to become familiar with Hydra, Crater, and Corvus in the southern sky. See the sky map to determine their orientation to Leo, Virgo, and Libra.

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.

VISIBLE PLANETS
Evening (Before Midnight)
Jupiter – The brightest object above the eastern horizon in early May is Jupiter. Find it overhead around midnight. May 6-8 a waxing gibbous moon grazes past Jupiter and blue star Spica. By month’s end Jupiter is overhead before 10:00pm and sets before morning twilight. (Magnitude -2.3 in Virgo)
Mars – The red planet sets in the last stages of twilight surrounded by red stars Aldebaran (Taurus) and Betelgeuse (Orion). (Magnitude +1.6 in Taurus)
Saturn – Saturn rises just before midnight in early May, before 11pm at midmonth, and before 10pm at the end of the month. (Magnitude +1.1 in Sagittarius-Ophiucus)
Morning (At Twilight)
Jupiter – In early May compare the brightness of Jupiter setting on the western horizon with Venus rising on the eastern horizon. (Magnitude -2.3 in Virgo)
Saturn – Look for Saturn above the SW horizon in early morning twilight. (Magnitude +1.1 in Sagittarius-Ophiucus)
Venus – Venus pierces the eastern horizon before astronomical twilight begins to brighten the surrounding sky. (Magnitude -4.6 in Pisces)

MOON HAPPENINGS
May 2 – Waxing first quarter moon lights the evening sky then sets soon after midnight.
May 10 – Full moon (3:42pm) rises at 8:13pm.
May 18 – Dark evening skies return with the waning last quarter moon rising after midnight.
May 25 – New moon (1:44pm) yields dark skies for several nights.

(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.)

Twilight is often the best time to look for Venus and Mercury because they frequently rise or set within one-half to one hour of sunrise or sunset. Twilight transitions between night and day in three stages at each end of the day. Morning twilight begins with astronomical twilight as the eastern horizon brightens —about 1-1/2 hours (nearly 2 during summer months) before sunrise when the sun is 18 ̊ below the horizon. Nautical twilight takes over for another 30-40 minutes—as the sun passes 12 ̊ below the horizon and the overhead sky turns blue and color returns to the surrounding landscape. The final stage—civil twilight—begins when the sun ascends to 6 ̊ below the horizon and provides adequate light for most outdoor activities for the half hour before the sun crests the horizon. The opposite progression occurs after sunset. Civil twilight covers the period after sunset during which daytime light quality persists for about one-half hour. Color then fades from the landscape during the 30-40 minute period of nautical twilight during which the overhead sky darkens while the western sky retains color. Astronomical twilight then transitions to night skies that are now darkened along the horizon.

CELESTIAL HAPPENINGS
Comets are notoriously unpredictable, but it would be disappointing to miss a good one. Comet C/2015 V2 (Johnson) could reach 6th magnitude during May. Extend the line from the upper right arm of Hercules southward grazing the western edge of Boötes. At the beginning of May Comet Johnson will be a little beyond the arm of Hercules. By midmonth look for it near the SE point star of the club of Boötes. The comet continues along this line, passing Corona Borealis but not traveling as far as Arcturus (Boötes). Sixth magnitude objects shine at the edge of naked eye visibility, so use binoculars to locate it. Go to http://www.cometwatch.co.uk/ for updates.

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.

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.

MAJOR METEOR EVENTS

Shower

Peak
(May)

Range
(May)

Constellation
Radiant

Rate
(/hr)

Details

Conditions

Eta
Aquarids

5/6
6/7

3-9

Aquarius

10-30

Swift with persistent trains just before morning twilight. Fireballs common after May 9.

Waxing gibbous moon
sets in early morning twilight
(hour earlier on May 5)

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.
 
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