Week of December 2, 2013

This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Monday, December 2.  All times are given as local St. Louis time (Central Standard 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, December 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 7:01 a.m. on Monday, December 2 and sunset is at 4:40 p.m. providing us with less than 10 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 6:14 p.m. this week.  For those with a sun dial, solar transit or local noon occurs around 11:51 a.m. this week.  We are entering our last few weeks of fall as the Winter Solstice occurs this month on December 21. 

Moonrise for Monday, December 2 occurs at 6:27 a.m.  Moonset will occur at 4:43 p.m.  The Moon starts this week at first quarter phase and ends with a waning crescent phase.  New Moon occurs on December 2 and will exhibit a waxing crescent phase for the rest of the week. 

International Space Station (ISS) Observing

The next visible passes of ISS over St. Louis are all evening passes.  All passes this week are good but the best occur on December 8 and 9.   See the table below for information regarding this pass.

Catch ISS flying over St. Louis in the evening hours starting Monday, December 2. 




Max. altitude











07 Dec











08 Dec











09 Dec











09 Dec











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


Mercury has once again risen out of the glare of the Sun.  It rises at 5:51 a.m. and should be visible by 6:15 a.m. for those with clear eastern horizons.  If you can spot Mercury grab a pair of binoculars and you can find Saturn and the double star Zubenelgenubi.  Maximum eastern elongation occurred on November 17th so Mercury is already on its way back around the Sun.  Look for Mercury while you can as twilight will rob us of this elusive planet soon.


The brightest planet in the sky is well into another evening apparition becoming visible about 20 minutes after sunset.  Venus will be low to the horizon and any trees or buildings southwest of you may obscure it from view.  Venus is currently seen in the constellation Sagittarius and will set by 7:27 p.m.  If you have binoculars at home you should notice that Venus in a crescent phase.  Due to Venus being closer to the Sun it is always in a phase similar to those we see the Moon exhibit.  The difference is Venus is always closer to the Sun so we never see a full Venus.  As Venus approaches its inferior conjunction in January next year, Venus will exhibit a thinner and thinner crescent shape.    


Mars is now in the constellation Virgo and will rise around 12:58 a.m. this week.  For those awake around 2:00 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 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 evening skies.  This week it will rise around 7:20 p.m. becoming visible roughly 30 minutes later.  Just above and to the east of Jupiter you will see the 1st magnitude stars Castor and Pollux.  Looking at these stars and then comparing them to Jupiter you will see that the stars are twinkling and Jupiter is not.  The twinkling you see is called scintillation which is a distortion of the stars light by Earth’s atmosphere.  Testing for scintillation is how you can distinguish stars from planets.  Jupiter will be at opposition on December 2, 2013.  After this date Jupiter will be rising as the Sun is setting.

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. 

For December we will be doing things a little different.  Instead of highlighting a constellation for December we will be tracking down some of the closest stars to the Sun.   Observing projects like this are a good way to refine your observing skills.  They also serve as a nice alternative for when you want something more than the same old faint fuzzies you have been looking at for the last few months.  All of the stars chosen for this month will be visible in binoculars and some will be visible to the naked eye. 

Week one of our expedition through our stellar neighborhood will bring us to two of the closest and brightest stars in the sky; Sirius and Procyon.  These two stars are found in the winter circle and will be visible by 10:00 p.m. 

Sirius is the brightest star in the night sky shinning at magnitude -1.74 and it is the 6th closest to the Sun.  It is a white A-Class hydrogen fusing star.  It has a smaller and hotter companion known as Sirius B that has evolved into a white dwarf star at the end of it existence.  Sirius B is the remnant core of a more massive star that was likely 5 to 7 times more massive than the Sun.  All that remains of Sirius B is a dense hot core of carbon and oxygen.  This dense core is only 0.92 times the size of Earth and shines with a luminosity of 2.8 percent of the Sun’s total output.  Sirius B is very difficult to see due to the intensely bright glare of its partner Sirius A. 

Procyon is the 8th brightest star in the night sky shining at a magnitude of 0.34 and it is the 15th closest star to the Sun.  Like Sirius, Procyon is a binary system with the main component star (A) being a hot white F-Class star and the secondary star (B) is a white dwarf star at the end of its life.  Both of the white dwarfs discussed in this section are two of three white dwarfs that helped identify and understand what white dwarfs actually are.

To find both Sirius and Procyon, look for Orion the Hunter and his famous three belt stars.  Once you have found the belt follow the three stars to the left of the belt and the brightest star you see will be Sirius.  Looking east of the belt will bring you to Procyon in Canis Minor.  Both of the stars are members of what many observers call the Winter Circle.  This is a group of stars that circles Orion and helps identify most of the winter constellations.  For those just beginning with backyard astronomy this structure is in my opinion the best place to start.  Use the maps below to help identify the star Sirius and Procyon. 



2013 Year of the Comet Part II

Earlier in the year we talked about 2013 as being year of the comet.  In the spring we had Comet PANSTARRS and for the end of the year we mentioned Comet ISON that was first predicated to become visible to the naked eye and had the chance to become as bright as the full moon.  Well, so far the year of the comet has not panned out as people were hoping for. 

Comet PANSTARRS was supposed to become visible to the naked eye but for most it remained just beyond naked eye visibility.  It was still quite beautiful through binoculars and telescopes but it did not break the naked eye threshold for most observers. 

Perihelion for Comet ISON has now come and gone.  Like many comets ISON failed to survive its close approach to the Sun.  As a consolation for the demise of Comet ISON there are two other comets you can see in the morning skies.  These comets are named Lovejoy (C/2013 R1) and Linear X1.  Comet Lovejoy is easy to see in binoculars and Linear X1 will require a telescope.  Find out more information about these two comets and the demise of Comet ISON below.

Articles with Comet ISON Updates






General Comet Information





Star Charts Showing Comet Locations in the Sky



Comet Linear X1 Finder Chart

Comet Update 12/02/2013:

Comet Lovejoy (C/2013 R1): This comet remains a great comet through a pair of binoculars and can now be found in the constellation Bootes. It is shinning at magnitude 4.3 making it an easy target in a pair of binoculars and should be visible to the unaided eye away from city lights.  Use the finder chart above to locate this comet.

Comet ISON (C.2012 S1): This comet has set the standard for unpredictable comets.  The year we waited for Comet ISON to approach the Sun was full of speculation and ultimately ended in disappointment.  On Thanksgiving ISON reached perihelion and looked like it broke apart just before reaching this point.  The day ended with comet hunters bummed because the comet of the century was a bust. Most were surprised the day after when waking up to new SOHO images that revealed some of Comet ISON may have survived.  As it moved out of the Sun’s glare it started to brighten again.  This unfortunately proved to be false hope as the cloud of debris we were seeing started to dim.  As it stands now Comet ISON is nothing more than a cloud of dust moving along the comet’s original orbit.  Comet ISON fresh from the Oort cloud could not handle the heat of the Sun.  Sadly this ends the chapter of another comet that was predicted to be amazing and fizzled before it had a chance to shine.  In the month or two proceeding ISON’s perihelion amateur and professional astronomers were able to take some amazing images of the doomed comet.  These will have to tide us over until the next great comet is discovered.  Scientists will still learn from what they saw and hopefully you were able to get out on some of the mornings while the comet was still visible.  We will say goodbye to Comet ISON with its parting shot around the Sun.  Linked below will be the most current image from SOHO detailing ISON’s demise. (So cool!)


Comet Linear X1: This comet is hanging at 9th magnitude so it should still be visible in small telescopes.  Use the link above to find daily locations for this comet.

NASA Mission of the Month

Each month we will be celebrating a NASA mission of the month.  This month’s mission is the Solar and Heliospheric Observatory (SOHO).  This is a telescope that dedicates it’s time to observing the Sun.  Telescopes like SOHO and its predecessor the Solar Dynamics Observatory (SDO) have revolutionized the fields of solar physics and stellar astronomy.  Our understanding of how the Sun functions has changed dramatically since the launch of SOHO.  In addition to the Sun, SOHO has helped observe comets, asteroids and anything else that moves within its field of view.  It is a fascinating telescope that provides us with a front row seat to the most important object in our solar system.  To learn more visit


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, November 1, 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 December 6, join us indoors in our planetarium theater for a special showing of “The Sky Tonight”.  There will be four short star shows that will show the night sky from St. Louis. Show times start at 6 p.m. and occur every half hour.   As there are star shows there will be only one Laserium show on all First Fridays.  This show begins at 8:30 p.m.  Information for laser shows can be found at http://www.slsc.org/laserium

Looking to the future, the James S. McDonnell Planetarium will be featuring a potential new fulldome digital video projection system allowing us to view the cosmos from beyond the confines of the surface of the Earth in brilliant color and high resolution.  We will preview a piece of this new system featuring the Carl Zeiss VELVET projectors this evening during 4 special viewings of The Sky Tonight at 6 pm, 6:30 pm, 7 pm and 7:30 pm.

These free, indoor star programs will introduce you to the current night sky, the planets, and the seasonal constellations. Doors open 15 minutes before show time. Shows begins at 6 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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