Week of May 6, 2013

This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Monday, May 6.  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 5:58 a.m. on Monday, May 6 and sunset is at 7:48 p.m. providing us with 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 9:41 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 6 is at 3:58 a.m. and moonset is at 5:00 p.m.  On Monday, May 6 the Moon will be exhibiting a waning crescent phase with roughly 11% of the lunar disk illuminated.  An interesting challenge is available this week on Friday, May 10.  If you have binoculars at home go outside about 15 minutes after sunset which will be at 8:01 p.m. for the 10th.  Scanning the west low to the horizon you will find Venus and a very young waxing crescent moon.  If you spot the Moon you can calculate how old it is by measuring the time elapsed since new moon.  New Moon occurs at 9:28 p.m. on Thursday, May 9.  See how young of a Moon you can catch this month before it sets on the 10th at 8:51 p.m.

International Space Station (ISS) Observing

ISS passes over St. Louis for the next two weeks starting Monday, May 6 are all early morning passes.  The best pass comes on the morning of Saturday, May 18. 

Catch ISS flying over St. Louis in the morning hours the week of Monday, May 6. 




Max. altitude











16 Apr











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18 Apr











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:


The Planets Visible Without A Telescope


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 8:43 p.m. 


The planet Jupiter will be visible shortly after sunset and sets around 10:28 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. 


Look for the ringed planet shortly after sunset low in the southeast.  Currently Saturn is found in the constellation Libra just to the west of the bright stars Zubeneschamali and Zubenalgenubi. 

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. 


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.                     

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.


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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