Week of September 2, 2013

This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Monday, September 2 .  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, September 6, 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 6:32 a.m. on Monday, September 2 and sunset is at 7:28 p.m. providing us with roughly 13 hours of daylight.  Even after sunset, the light from the Sun will still illuminate our sky for about one hour and 30 minutes.  This period of time is called twilight, which ends around 9:0 p.m. this week.  For those with a sun dial, solar transit or local noon occurs around 1:00 p.m. this week. 

Moonrise for Monday, September 2 is at 4:47 a.m. and moonset is at 6:15 p.m. on the following day.  The Moon will be exhibiting a waning crescent phase with roughly 3% of the lunar disk illuminated.  New moon occurs on September 5.      

International Space Station (ISS) Observing

The next visible passes of ISS over St. Louis will not occur again until September 10. See the table below for information regarding these passes. 

Catch ISS flying over St. Louis in the morning hours starting Monday, September 2. 




Max. altitude











10 Sep











12 Sep












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 well into another evening apparition becoming visible about 30 minutes after sunset.  Venus will be low to the horizon and any trees or buildings west of you may obscure it from view.  Venus is currently seen in the constellation Virgo and will set by 8:58 p.m. 


Mars is finally out of the Sun’s glare rising at 3:27 a.m.  For those awake around 4:00 a.m. look to the east and you will see a reddish-orange object just above the horizon.  Mars will be seen earlier each week as it as we start to catch up with it in our orbit.  Mars will be close to us again in 2014 reaching opposition on April 8, 2014.  Fans of Mars rejoice it is back and on its way to another close approach.


The largest planet in our solar system has returned to our skies.  This week it will rise around 1:54 a.m. becoming visible roughly 30 minutes later.  It is currently paired with Mars in the morning skies. 


Look for the ringed planet shortly after sunset high in the south.  Currently Saturn is found in the constellation Virgo just to the east of the bright star Spica.  Saturn will set by 9:51 p.m.

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. 

The constellation for September will be Cassiopeia the Queen.  As September marks the transition from summer to fall, we will start the season off with the constellation that many use as their guide for the fall skies.  In Greek mythology Cassiopeia was part of the founding myth of Perseus.  She was a queen that boasted about her beauty and this vanity angered the gods.  As a punishment she was forced to sacrifice her daughter Andromeda to appease the titan Cetus who was unleashed by Poseidon.  Cassiopeia’s role in the myth of Perseus is minor but it is an important part of this founding myth and its potential historical significance.  For fans of Greek myth the story of Perseus and those involved with him helped shape what would become the pantheon of the 12 Olympian Gods.

Finding Cassiopeia is easy as she appears as a bright W-shape of stars.  The W-shape will be seen high in the northeast skies after 9 p.m.  Finding Cassiopeia is a great way to begin our exploration of the fall skies.  Most of the constellations in the fall sky can be found by star hopping from the bright stars of Cassiopeia.     

The first object we will explore in Cassiopeia is M52.  This is an open star cluster that lies at an approximate distance of 5,000 light years.  Compared to many of the other open clusters we have talked about M52 is very young at an age of approximately 35 million years.  Shining at a magnitude of 7.3, M52 can be seen through a good pair of binoculars as a faint nebulous patch of light.  4-inch or larger telescopes will start to reveal it as a collection of stars that has a bit of a V-shape to it. 

To find M52 locate the stars Alpha and Beta Cassiopeiae.  From these stars draw a line extending roughly 6.5 degrees northwest of Beta Cassiopeiae and you will find M52.



Nova star Del 2013

On August 14th Koichi Itagaki discovered the nova star Del 2013 shining at a magnitude of 6.8.  Nova stars are a type of variable star that typically involve a binary system with the primary star being a white dwarf and the secondary being a cooler low mass star.  As they orbit each other the white dwarf star accretes or steals material from its companion.  This material builds up and when the temperature and pressure is high enough a thermo-nuclear event occurs.  This explosion causes the star to flare in brightness by about 10 magnitudes.   Over the next few days astronomers around the world followed Del 2013 as it continued to brighten to about 4.5 magnitude.  It was last reported at 4.8 magnitude and will likely remain here for the next few days.  Many novae will only be seen once in a human lifetime so try and see it while the seeing is still good.  Novae typically flare dramatically in brightness and then slowly fade back out of view.  You should have at least a week to see Del 2013 through just a pair of binoculars.  For those interested in observing this rare sight use the second map linked below.

Update 8/26/2013: Del 2013 is now shining at roughly magnitude 6.  This will make it difficult in city skies to spot it in a pair of binoculars.  Small telescopes will still get the job done and with moonlight no longer a major issue it should still be visible through most telescopes. - See more at: http://www.slsc.org/week-of-august-26-2013#sthash.uqtrOhTr.dpuf 

Update 9/3/2013: Del 2013 is now shining at 7.2 magnitude.  It is still visible in a pair of 10x50 binoculars but as it continues to fade a telescope will needed to find it.  Reference the link below of the most up to date information regarding nova star Del 2013. 


NASA Mission of the Month

Each month we will be celebrating a NASA mission of the month.  This month’s mission is the historic and current Voyager missions.  Voyager 2 was launched on August 20, 1977 and Voyager 1 was launched on September 5, 1977.  The original voyager mission was designed to send spacecraft on a grand tour of the outer planets in our solar system.  Voyager 1 would fly by Jupiter and Saturn while Voyager 2 would fly by Uranus and Neptune.  This leg of the mission was completed in 1989 with Voyager 2’s flew by Neptune.  Included on both spacecraft was a golden record that contained information relative to our location in the galaxy, various other scientific data, greetings in numerous different languages and pictures of the Earth and its life forms.  This record was included in case the spacecraft were ever found by intelligent life forms.  With this in mind both spacecraft were sent on trajectories that will carry them close to some our neighboring stars in the galaxy. 

Twelve years after launch the Voyager mission received an extension.  The new mission objective is called the Voyager Interstellar Mission which is designed to extend NASA’s exploration of the solar system beyond the outer planets and to explore the outer limits of the Sun’s sphere of influence.  Voyager 1 has nearly reached the extent of the Sun’s influence and will likely be in interstellar space in the next few years.  This will make it the first human made spacecraft to ever leave the solar system.  To learn more follow the links 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. 

Our next Star Party will be held on Friday, September 6, 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 September 6, 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 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 7 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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