Week of August 5, 2013

This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Monday, August 5.  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 6:06 a.m. on Monday, August 5 and sunset is at 8:07p.m. providing us with roughly 14 hours of daylight.  Even after sunset, the light from the Sun will still illuminate our sky for about one hour and 40 minutes.  This period of time is called twilight, which ends around 9:50 p.m. this week.  For those with a sun dial, solar transit or local noon occurs around 1:07 p.m. this week. 

Moonrise for Monday, August 5 is at 5:02 a.m. and moonset is at 7:08 p.m.  The Moon will be exhibiting a waning crescent phase with roughly 2% of the lunar disk illuminated.  New moon occurs on August 6.   

International Space Station (ISS) Observing

Visible passes of ISS over St. Louis for the next week are mostly evening passes.  The best passes come on the evenings of August 5 and 7.  See table below for information regarding these passes.

Catch ISS flying over St. Louis in the morning and evening hours starting Monday, August 5. 

Date

Mag

Starts

Max. altitude

Ends

Time

Alt.

Az.

Time

Alt.

Az.

Time

Alt.

Az.

05 Aug

-2.9

20:48:07

10

SSW

20:51:17

41

SE

20:54:28

10

ENE

05 Aug

-0.9

22:25:19

10

W

22:28:07

24

NNW

22:30:56

10

NNE

06 Aug

-2.1

04:57:48

23

SW

04:57:56

23

SW

05:00:39

10

S

06 Aug

-1.6

21:36:19

10

WSW

21:39:27

36

NNW

21:42:36

10

NE

07 Aug

-2.7

20:47:31

10

WSW

20:50:50

62

NW

20:54:10

10

NE

07 Aug

-0.1

22:26:15

10

NW

22:28:07

14

NNW

22:29:59

10

NNE

08 Aug

-0.4

21:36:54

10

WNW

21:39:19

18

NNW

21:41:45

10

NNE

09 Aug

-0.9

20:47:43

10

W

20:50:35

26

NNW

20:53:27

10

NNE

10 Aug

-0.1

21:35:05

10

NW

21:39:21

12

NNW

21:40:38

10

N

11 Aug

-0.3

20:48:32

10

NW

20:50:30

15

NNW

20:52:28

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

Mercury has started another morning apparition rising at 4:41 a.m.  Currently it will be difficult to pull mercury out of the morning twilight skies and if you have any buildings or trees east of you it will be difficult to see the planet.  This will not be the best apparition of Mercury but take a look and see if you can spot the elusive planet.  Look for Mercury paired with Mars and Jupiter low in the eastern skies around 5 a.m.

Venus

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 Leo and will set by 9:36 p.m. 

Mars

Mars is finally coming out of the Sun’s glare during the hours of morning twilight.  For those awake around 4:30 a.m. look to the east and you may find 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.

Jupiter

The largest planet in our solar system has returned to our skies.  This week it will rise around 3:23 a.m. becoming visible roughly 30 minutes later.  It is currently paired with Mars and Mercury in the morning skies. 

Saturn

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 11:40 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. 

As this is our last full month of summer we will do things a bit different.  This month we will cover some of the overlooked constellations of the summer sky.  These will be the smaller minor constellations that are often lost amongst the larger more famous constellations.  Each week we will add a constellation to look for and a few of its highlights.

The first of our overlooked constellations will be Sagitta the Arrow.  There seems to be some debate as to what arrow this is supposed to represent but most seem to agree it is an arrow relevant to the story of Aquila the Eagle.  This was Zeus’s eagle that pecked at Prometheus nightly as a punishment for stealing fire from the gods and giving it to humankind.  Sagitta the arrow is believed to be either the arrow that Hercules used to kill Aquila saving Prometheus from this eternal torture or the arrow that Aquila carried in his talons.

To find Sagitta look for the bright Summer Triangle containing the three stars Denib, Vega and Altair.  Once you have found Altair look about 8 degrees north of the bright star and there will be five star s that look like a small arrow.  Sagitta is one of the smallest constellations so it will be easy to miss. Using the star chart linked below you should have no problem identifying this small group of stars.

It may be small but Sagitta has a number of interesting objects to look at.  One of these objects is the eclipsing binary (EB) called U Sagittae.  This is a pair of stars that orbits one another in such a way that they eclipse each other from our perspective.  During the primary eclipse of the pair the star will fade in brightness from 7.9 to 9.2 magnitude. U Sagittae’s minima will last for a little more than one hour.  The primary eclipse of this EB star occurs every 3.25 days.  It will be a suitable target for binoculars and small telescopes.  To find U Sagittae look 5 degrees west of Alpha Sagittae and then 1.75 degrees to the north.  This will be a tough find but well worth the effort.  It is one of the better EB stars in the northern hemisphere. 

Another interesting object in Sagitta is the globular star cluster M71.  It is a class X-XI cluster meaning it is a very loose globular cluster according to the Shapley-Sawyer ranking system.  It has the mass of approximately 17,000 stars that are found to be roughly 13,000 light years away from us. 

Shining at a magnitude of 8.2, M71 is a target for a good pair of binoculars or a small telescope.  It will be easy to find as it is directly between the bright stars Delta and Gamma Sagittae.  Pan back and forth between these stars and you should have no problem finding M71.

Sagitta may be small but it is loaded with goodies for the careful observer.  Get a good map for Sagitta and there are many other things to look for besides the two we listed.  Unfortunately most of these objects are best viewed through a telescope.

http://iau.org/static/public/constellations/gif/SGE.gif

http://messier.seds.org/m/m071.html

2013 Perseid Meteor Shower

We are approaching the peak activity of one of the best meteor showers for northern hemisphere observers known as the Perseids.  Every August around the 12th and 13th we are treated to a flurry of meteors produced by a periodic comet called Comet Swift-Tuttle.  This is a 16 mile wide mountain of ice and other material that takes roughly 133 years to orbit the Sun.  The last time it was close to the Sun was in the year 1992.  As comets like this orbit the Sun they leave behind a stream of debris that the Earth can pass through usually once a year.  As the Earth passes through these debris streams little comets particles, usually no larger than a grain of sand, smash into our atmosphere at high velocities.  As the meteor smashes through the atmosphere gases are ionized causing the signature streak of light to appear.  The brightest meteors are called bolides or fireballs.  These are caused by softball sized pieces of comets that persist longer and can even be seen to fracture or explode.  The Perseids are known for producing numerous bolides.

The Perseids are best observed after midnight on the mornings of August 12th and 13th looking to the northeast.  Meteor showers get their names from the constellation that houses the shower’s radiant or their apparent source of meteors in the sky.  The name Perseids indicates that you will want to look towards the constellation Perseus which is rising in the northeast by 10:30 p.m.  Unfortunately for North America the peak hours occur when it is still daytime.  Regardless of this you can still count on seeing nearly 100 meteors per hour from a dark location.  If you plan to observe in areas with light pollution you will only see 10 to 20 meteors per hour.  Below you will find links for more information regarding the great Perseid meteor shower.

http://science.nasa.gov/science-news/science-at-nasa/2013/26jul_perseids/

http://imo.net/files/data/calendar/cal2013.pdf

NASA Mission of the Month

Each month we will be celebrating a NASA mission of the month.  This month’s mission is the Mars Science Laboratory (MSL).  The MSL rover now called Curiosity was launched on November 26, 2011 and successfully landed on Mars August 5/6, 2012.  It is a mission that will be exploring the habitability of the Martian environment looking for evidence that it could have supported life in the past.  To learn more about the MSL mission visit

http://mars.jpl.nasa.gov/msl/

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, 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

http://www.slsc.org/laserium

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