Week of May 20, 2013

This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Monday, May 20.  All times are given as local St. Louis time (Central Daylight Time).  For definitions of terminology used in the night sky update, click the highlighted text.

Information updated weekly or as needed.

Join us for our next star party, Friday, June 7, 2013 held in association with the St. Louis Astronomical Society. For details, see the information at the bottom of this page.

The Sun and the Moon

Sunrise is at 5:45 a.m. on Monday, May 20 and sunset is at 8:11 p.m. providing us with over 14 hours of daylight.  Even after sunset, the light from the Sun will still illuminate our sky for nearly two hours.  This period of time is called twilight, which ends around 10:00 p.m. this week.  For those with a sun dial, solar transit or local noon occurs around 12:58 p.m. this week.

Moonrise for Monday, May 20 is at 3:21 p.m. and moonset is at 3:09 a.m. on the following day.  On Monday, May 20 the Moon will be exhibiting a waxing gibbous phase with roughly 75% of the lunar disk illuminated.  Full moon occurs on Friday, May 24 at 11:26 p.m.  May’s full moon is called the Full Flower Moon.

International Space Station (ISS) Observing

ISS passes over St. Louis for the next two weeks starting Monday, May 20 are all early morning passes.  The best passes come on the mornings of May 21, 22 and 24. 

Catch ISS flying over St. Louis in the morning hours the week of Monday, May 20. 

Date

Mag

Starts

Max. altitude

Ends

Time

Alt.

Az.

Time

Alt.

Az.

Time

Alt.

Az.

21 May

-3.2

03:56:44

51

W

03:57:22

68

NW

04:00:42

10

NE

22 May

-2.0

03:09:37

38

ENE

03:09:37

38

ENE

03:11:51

10

ENE

22 May

-1.1

04:43:03

10

WNW

04:45:32

19

NNW

04:48:01

10

NNE

23 May

-0.2

02:22:24

12

ENE

02:22:24

12

ENE

02:22:45

10

ENE

23 May

-1.6

03:55:15

22

WNW

03:56:26

27

NNW

03:59:21

10

NNE

24 May

-2.0

03:07:54

39

N

03:07:54

39

N

03:10:33

10

NE

24 May

-0.5

04:43:22

10

NW

04:44:45

12

NNW

04:46:07

10

N

25 May

-0.6

02:20:28

20

NE

02:20:28

20

NE

02:21:35

10

NE

25 May

-0.6

03:53:23

10

WNW

03:55:25

15

NNW

03:57:28

10

NNE

26 May

-1.1

03:05:44

20

NW

03:06:05

20

NNW

03:08:39

10

NNE

27 May

-0.8

02:18:03

22

N

02:18:03

22

N

02:19:42

10

NNE

27 May

-0.2

03:53:40

10

NNW

03:54:16

10

N

03:54:53

10

N

28 May

-0.1

01:30:16

12

NE

01:30:16

12

NE

01:30:37

10

NE

28 May

-0.3

03:03:10

10

NW

03:04:42

13

NNW

03:06:14

10

NNE

29 May

-0.5

02:15:10

16

NNW

02:15:10

16

NNW

02:17:18

10

NNE

30 May

-0.2

01:27:07

16

NNE

01:27:07

16

NNE

01:28:12

10

NNE

30 May

 0.0

04:39:55

10

N

04:41:06

11

NNE

04:42:17

10

NE

31 May

 0.0

00:38:54

10

NE

00:38:54

10

NE

00:38:57

10

NE

01 Jun

-0.7

01:23:13

13

NNW

01:23:32

13

NNW

01:25:15

10

NNE

Magnitude (Mag): The Measure of brightness for a celestial object.  The lower the value is, the brighter the object will be.

Altitude (Alt):  The angle of a celestial object measured upwards from the observer’s horizon.

Azimuth (Az):  The direction of a celestial object, measured clockwise from an observer’s location with north being 0°, east being 90°, south being 180° and west being 270°.

For information about ISS flyovers and other visible satellites, visit www.heavens-above.com

Detailed information regarding all unmanned exploration of our universe, missions past, present, and planned, can be found at Jet Propulsion Laboratories:

http://www.jpl.nasa.gov/

The Planets Visible Without A Telescope

Mercury

The elusive planet Mercury is once again with us in the early evening.  You only have a short time to catch this planet as it sets at 9:03 p.m.  Mercury will continue to climb higher in the western skies just after sunset until June 12 when it reaches maximum eastern elongation.  On the 24th of May, Mercury and Venus will reach conjunction.  The two planets will be less than two degrees apart. 

Venus

The brightest planet in the sky is starting another evening apparition becoming visible about 20 minutes after sunset.  For the time being it may be difficult to spot since it will be low to the horizon and any trees or buildings west of you will likely obscure it from view.  As May progresses Venus will climb higher in the sky and will be joined by Jupiter and Mercury for a planetary conjunction at the end of the month.  Venus is currently seen in the constellation Taurus and will set by 9:14 p.m. 

Jupiter

The planet Jupiter will be visible shortly after sunset and sets around 9:47 p.m.  Grab a pair of binoculars and see how many of the Galilean moons you can see.  Depending on when you look you should be able to see all four; Io, Europa, Ganymede and Callisto.  As you watch them sketch their locations relative to Jupiter and you will be following in the footsteps of Galileo. 

Saturn

Look for the ringed planet shortly after sunset low in the southeast.  Currently Saturn is found in the constellation Virgo just to the east of the bright star Spica.  Saturn will set by 4:51 a.m. 

Planetary Conjunction: Mercury, Venus and Jupiter

If you have never seen a planetary conjunction now is your chance.  Starting on May 24th Mercury and Venus will be seen close together in the sky.  Two days later on the May 26, Jupiter will join the others.  These three planets will be less than 2.5 degrees apart.  This will be your last chance to see three planets this close together until 2026.  The three planets will stay close together until June 7th when they start to separate once again.  From May 24 – 29 these three planets will be in conjunction with each other on various days.  A conjunction occurs when two astronomical objects share the same right ascension.  Listed below are the dates of conjunctions associated with this grouping of three planets. 

May 24 – Mercury and Venus

May 26 – Mercury and Jupiter

May 28 – Venus and Jupiter

To learn more follow the link bellow.    

http://www.skyandtelescope.com/observing/highlights/The-May-June-2013-Planet-Dance-192020551.html

Constellation of the Month

Each month we will highlight one constellation and some of the objects that can be found within the boundaries of that constellation.  At the start of the month we will list only a few of these objects and each week we will add another to the list.  Some objects will be visible to the unaided eye and some may require a telescope.  Many of the objects listed will require a map of the sky to find or may require repeat observations to notice various properties.  Links to star charts and other information that will be useful in identifying the objects listed will be given at the end of each week’s section. 

This month our constellation is Ursa Minor.  Also known as the Little Bear, this constellation can be found in the circumpolar sky.  The term circumpolar indicates that the stars which make up the constellation never really rise or set but rather circle around the North Star.  Due to its location in the circumpolar sky, Ursa Minor is visible all year long.  The name Ursa Minor comes from the ancient Greek interpretation of this star pattern.  The story involves a Nymph of the Moon goddess Artemis named Callisto.  She was wooed by Zeus and gave birth to a son named Arcas.  Fearing the anger of Artemis and his wife, Zeus turned Callisto into a bear.  One day her son was hunting and came across a great bear who unbeknownst to him was his mother.  As he knocked his arrow and took aim, Zeus intervened and turned Arcas into a bear.  Now a bear, Arcas recognized his mother and the two were then placed into the sky together safe from hunters and the ire of Hera.  This story led to the formation of Ursa Minor (Arcas) and Ursa Major (Callisto).

To find Ursa Minor locate the Big Dipper high in the northern skies.  Using the two stars at the end of the dipper’s bowl, trace a straight line above the bowl until you find Polaris.  This will be the brightest star in Ursa Minor.  Once you have found Polaris use the star chart linked below to find the rest of the stars of Ursa Minor. 

http://www.iau.org/static/public/constellations/gif/UMI.gif

Object of the week for April 29 is the Little Dipper.  Even though the Little Dipper is well known to most, it is not nearly as easy to find as most would think.  Frequently people think that the star cluster M45 (Pleiades) is the Little Dipper.  It does indeed look like a small spoon but it is never seen in the north.  The common method used to find the Little Dipper is to use the last two stars in the bowl of the Big Dipper.  Just like was mentioned above, follow a straight line above the Big Dipper’s bowl and this will take you to the North Star.  The North Star is the last star in the Little Dipper’s handle.

The little dipper also serves as a good lesson in light pollution.  In cities most of the stars in the Little Dipper are very difficult to see due to light pollution drowning out their light.  The more stars you can see in the Little Dipper, the better your viewing conditions will be.  It is also important to mention that if you leave North America, it is no longer called the Little Dipper.  Both the Big and Little Dippers are not constellations but rather are asterisms.  These are informal groupings of stars as opposed to the formal groupings we call constellations.

Lastly, the Little Dipper was chosen for our first object in May as it will serve as our reference point for the rest of the month.  Most of the objects we will cover in May are visible in just a pair of binoculars but they will be considerately more difficult to find.  It is important to have a strong reference point to base our explorations from.  

Object of the week for May 6 is an asterism called the Engagement Ring.  First off we should explain what an asterism is.  Asterisms are the informal patterns of stars as opposed to the constellations which are the formal groupings of stars astronomers use to organize the sky.  Both the Big and Little Dippers are asterisms.  The Engagement Ring asterism is found near the North Star.  To find the North Star follow the instructions above.  Once you have found the North Star grab a pair of binoculars and scan the area just below it and you will see a faint ring of 7th to 8th magnitude stars.  These stars make the ring’s band and the North Star represents the Diamond in the ring.  While you are looking at the North Star if available grab a telescope and try to split it into two stars.  Like most other stars, Polaris is a double star.  It will not be an easy split but it is doable in small telescopes at higher powers.

Object of the week for May 13 is a star called V UMi.  This star is a semi regular variable star that has a peak magnitude of 7.06 and minima of 8.7.  The cause of the brightness shift in this star is an internal pulsation that causes that star to flare in brightness roughly every 73 days.  Due to it being a semi regular variable, V UMi’s period of variability can change.  It is an M-class red giant star indicating that its internal pulsations cause the tenuous outer atmosphere of the star swell and becomes more luminous.

Since V UMi is a circumpolar star it can be monitored year round making it a great option for learning how to observe variable stars with longer periods of variability.  To find V UMi look for the star Eta Ursae Minoris.  This star is also called 21 UMi and is the bottom star on the inner edge of the Little Dipper’s bowl.  From here look about 4 degrees to the west and you will find V UMi.  To identify this star you will need to pay close attention to the fainter stars in the field of view.  To help with this there will be multiple links to maps that represent the star field around V UMi.  If you enjoy hunting down this variable star it is one of 153 variable stars on AAVSO’s list of binocular variables.  For those interested in finding more of these binocular variables the AAVSO list will also be posted.

http://www.iau.org/static/public/constellations/pdf/UMI.pdf

http://www.aavso.org/vsp/chart

http://www.aavso.org/aavso-binocular-program

Object for the week of May 20 is a concept more than an object.  We are all taught to find the North Star if we wanted to locate the direction north.  To do this you just follow the last two stars in the bowl of the Big Dipper above the bowl and you will find the North Star.  The star we call the North Star is Polaris and it is found at the end of the Little Dipper’s handle.  It may come as a surprise that this star will not always be the North Star nor has it always been.  Due to a motion called precession, the Earth’s poles change their orientation relative to the stars.  This motion can be perceived as a wobble much like a top when its axial rotation slows down.  The cause of precession is tidal forces induced by the Moon, Sun and to a lesser extent the other planets.  Earth takes roughly 26,000 years to make one precession cycle.

So what are some other stars that have been or will be North Stars?  Around the year 3000 CE, a star called Gamma Cephei will be closest to the north celestial pole.  In 14,000 years the bright star Vega will be closest to the north celestial pole.  In the past, a star in the constellation Draco, called Thuban, was the North Star.  Thuban was the North Star about 6000 years ago when the ancient Egyptians were building the great pyramids.  The ancient Egyptians developed complex cosmologies and even cultural traditions based on observing Thuban and other stars.  One common use was the telling of time.  Based on the position of the stars around the North Star, they knew the time of year.  They also recorded time with it.  Many of the funeral sarcophagi were adorned with star positions relative to their death.  Ancient Egyptian astronomy is quite fascinating and in part is still in use today.  Thanks to the ancient Egyptians we have a day divided into 24 hours. 

To Find Thuban and the other North Stars follow the links below.

Thuban

Gamma Cephei

Vega

NASA Mission of the Month

Each month we will be celebrating a NASA mission of the month.  This month’s mission is the historic Mercury Program.  The Mercury program ran from 1958 to 1963.  It was NASA’s first foray into manned space flight.  It entailed six manned missions and a number of other test flights that included sending a Rhesus Monkey and two Chimpanzees into space.  It was the program that proved we could put a human in space and have them orbit the Earth.  The Mercury missions were one person flights that launched aboard the Redstone and Atlas rockets.  To learn more about this historic program follow the link below.

http://www.nasa.gov/centers/kennedy/about/history/mercury7.html

50th Anniversary of the James S. McDonnell Planetarium

2013 marks the 50th anniversary of the James S. McDonnell Planetarium.  There are a number of events planned for the year that will celebrate the 50th anniversary.  For more information about the planetarium and the 50th anniversary, visit www.slsc.org

Our next Star Party will be held on Friday, June 7, 2013, from dusk until 10 p.m.
Weather permitting, the St. Louis Astronomical Society and the Science Center will set up a number of telescopes outdoors and be on-hand to answer your questions.  Telescope viewing begins at 8:00 p.m.  Regardless of the weather on May 3, join us indoors in our Planetarium Theater for “The Sky Tonight”.  Showtime is at 7 p.m. (Please note this time changed from 8:00 p.m.  to 7:00 p.m. due to Laserium shows starting a 8:30 p.m.)  

This free, indoor star program will introduce you to the current night sky, the planets, and the seasonal constellations. Doors open 15 minutes before show time. Shows begins at 8 p.m. Sorry, no late admissions due to safety issues in the darkened theater.

The St. Louis Astronomical Society hosts the monthly Star Parties at the Science Center which are held on the first Friday of each month. Our Monthly Star Parties are open to the public and free of charge.  For more information about the St. Louis Astronomical Society visit their website at www.slasonline.org

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