Week of July 15, 2013

This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Monday, July 15.  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, August 2, 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 5:49 a.m. on Monday, July 15 and sunset is at 8:25 p.m. providing us with nearly 15 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 10:21 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, July 15 is at 1:02 p.m. and moonset is at 12:17 a.m. on the following day.  Monday, July 15 is first quarter moon and full moon occurs on the following Monday.  This week marks the 44th anniversary of the Apollo 11 mission.  You can celebrate this historic mission by looking for the lunar mare called Mare Tranquillitatis.  This is the ancient lava flow that was chosen for their landing site and can be easily found with the unaided eye.  Follow the link below to find the mare and directions on how to find the location through a telescope.

http://www.digitalsky.org.uk/lunar/Apollo11/Finding-Tranquility-Base.html

International Space Station (ISS) Observing

Visible passes of ISS over St. Louis for the next 10 days are all morning passes.  The best passes come on the mornings of July 17, 19 and 20.  See table below for information regarding these passes.

Catch ISS flying over St. Louis in the morning hours the week of Monday, July 15. 

Date

Mag

Starts

Max. altitude

Ends

Time

Alt.

Az.

Time

Alt.

Az.

Time

Alt.

Az.

16 Jul

-0.6

04:06:52

10

SSE

04:08:07

12

SE

04:09:22

10

ESE

17 Jul

-3.1

04:53:31

15

SW

04:56:13

66

SE

04:59:34

10

NE

18 Jul

-2.2

04:07:13

30

SSE

04:08:02

35

SE

04:11:08

10

ENE

19 Jul

-0.9

03:20:51

17

ESE

03:20:51

17

ESE

03:22:24

10

E

19 Jul

-2.4

04:53:45

14

WSW

04:56:26

42

NNW

04:59:39

10

NE

20 Jul

-3.2

04:07:19

48

WSW

04:08:06

73

NW

04:11:27

10

NE

21 Jul

-2.0

03:20:48

39

ENE

03:20:48

39

ENE

03:23:07

10

ENE

21 Jul

-1.1

04:54:14

10

WNW

04:56:48

20

NNW

04:59:22

10

NNE

22 Jul

-0.2

02:34:15

12

ENE

02:34:15

12

ENE

02:34:36

10

ENE

22 Jul

-1.7

04:07:08

23

WNW

04:08:18

28

NNW

04:11:17

10

NNE

23 Jul

-1.9

03:20:31

38

N

03:20:31

38

N

03:23:06

10

NE

23 Jul

-0.5

04:55:49

10

NW

04:57:17

12

NNW

04:58:46

10

N

24 Jul

-0.5

02:33:51

18

NE

02:33:51

18

NE

02:34:50

10

NE

24 Jul

-0.7

04:06:44

11

WNW

04:08:40

16

NNW

04:10:47

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

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 9:56 p.m. 

Mars

Mars is finally coming out of the Sun’s glare during the hours of morning twilight.  It rises about one hour before the Sun which means for most it will be difficult to find.  For those awake around 4:45 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.

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 1:06 a.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. 

This month our constellation is Ophiuchus the Serpent Bearer.  Ophiuchus is associated with the myth of Aescupalius who was a healer of great fame in Greek myth.  He was the son of Coronis, a mortal woman who was courted by Apollo and became pregnant with his child.  While pregnant with Apollo’s child Coronis fell in love with a mortal man named Ischys.  Learning of this, Apollo’s sister Artemis became angry unleashing a quiver of arrows slaying Coronis.  Apollo saved his child and brought him to the centaur Chiron who in turn raised the boy and taught him medicine.  Aescupalius became so good at the art of medicine that Hades the god of the underworld became fearful that he would soon be able to raise the dead.  Hades complained to Zeus who agreed and regrettably decided that Aescupalius must die.  After Zeus killed the healer he honored him by placing him among the stars in the heavens.  Today we see him holding the serpent in the southern summer skies.  A supposed descendent of Aesculapius was Hippocrates.

To locate Ophiuchus look south in the summer months and you will find him standing just above the Milky Way’s core.  The easiest way to do this is to locate the fishhook shape of Scorpius and the teapot shape of Sagittarius which are found on the west and east sides of the galaxy’s core respectively.  Looking just above these two constellations you will see a large bell shape of stars extending up to Hercules.  This is a tough one to find as its bright stars are spread over a large part of the sky and as a result there is no real striking pattern that will jump out at you.  If you can find the surrounding patterns I have described you should be able to the brightest stars filling out the constellation Ophiuchus.  http://iau.org/static/public/constellations/gif/OPH.gif

I chose Ophiuchus as this month’s constellation for two reasons.  First it is not frequently talked about and more importantly it is filled with globular star clusters.  Globular clusters are the ancient dense star clusters orbiting around the Milky Way’s core.  They can contain tens of thousands to millions of stars that are billions of years old and are likely some of the earliest stars to form in the Milky Way.  Globular clusters are found in most galaxies and can number in the thousands.  The Milky Way has roughly 158 globulars whereas the giant elliptical galaxy M87 is thought to have about 13,000.  The closest globular cluster is roughly 7000 light years away from us and the most distant is over 40,000 light years away.  In the Milky Way we see two populations of globular clusters.  One is associated with our galaxy’s core and the other is associated with our galaxy’s outer halo.  This distinction indicates that some of our globulars were likely part of other galaxies captured by the Milky Way.  One important feature of stars in globular clusters is their metallicity.  This describes how rich in heavy elements a star is.  To astronomers any element heavier then hydrogen and helium are considered a heavy element.  All of these heavy elements were formed through nucleosynthesis in the heart of stars.  Therefore the stars we see with low levels of heavier elements in their spectrum were the progenitors to stars like the Sun which have higher amounts of heavier elements.  Stars with lower levels of heavier elements are called population II stars and these are what are typically found in globular clusters.  The formation of globular clusters is not completely understood.  Regardless of this fact they are important to the overall understanding of both stellar and galactic evolution.

There are 158 confirmed globular star clusters in the Milky Way with another roughly 20 candidates waiting for approval.  Most of these are found clustered around the galaxy’s core. You can imagine this by thinking of bees hovering around a beehive.  Of these globulars, Ophiuchus has potentially 30 of them, including 7 of the 29 included in the Messier catalog.    

Our first object for the month of July is the globular cluster M9.  This cluster can be found about 3 degrees southeast of the star Sabik also called Eta Ophiucii.  M9’s magnitude is 7.7 making it just visible to a pair of 10x50 binoculars.  Through binoculars it will appear as a faint patch of nebulous light and through small telescopes the bright core will begin to be resolved.  Not far from M9, two other globular clusters can be found.  NGC 6342 and 6356 can both be seen less than 2 degrees from M9.  Both will require a telescope and light pollution will cause problems.  http://messier.seds.org/m/m009.html   

Object for the week of July 8 is the globular cluster M107.  Discovered by Pierre Mechain in 1782 it was the last globular cluster put into the Messier catalog.  It shines at a magnitude of 7.9 and is about 21,000 light years away.  It is one of the globulars associated with the Milky Way’s halo and is moving towards us at a rate of 147 km/s.  It has a total of 25 confirmed variable stars and a number of confirmed blue straggler stars.  The estimated age of M107 is close to 14 billion years.  This date is an old estimation and does not agree with the current estimated age of the universe which currently is believed to be roughly 13.798 billion years old.  These numbers are likely to be further refined as we understand more about the universe and how to better determine the ages of stars.

Something to look for when observing globular clusters is the concentration of their stars.  Using the Shapely-Sawyer concentration classifications, astronomers rank globular cluster on a scale of I-XII based on how densely concentrated their stars are.  Class-I clusters are highly concentrated and Class-XII clusters exhibit almost no concentration.  Last week we discussed M9 which is a Class-VIII cluster which means it is rather loosely concentrated towards its center.  M107 is a Class-X cluster which indicates it is a loosely concentrated cluster. 

To find M107 look about 4 degrees south southwest of the bright star Zeta Ophiucii.  It is bright enough to be seen as a faint patch of nebulous light through 7x50 binoculars and will be an easy target through 4-inch telescopes.                                                                               http://messier.seds.org/m/m107.html                                                             http://www.iau.org/static/public/constellations/gif/OPH.gif

Object of the week for July 15 is the globular cluster M19.  This globular cluster is a class VIII cluster that shines at a magnitude of 6.8 and is approximately 28,000 light years.  M19 is associated with the center of the galaxy and lies about 5,200 light years away from our galaxy’s core.  One notable feature is how oblate the cluster is.  It has a very distinct ellipsoid shape that will stand out even in small telescopes.  This is likely caused by M19’s proximity to the core of the galaxy.  Gravitational interaction with the Milky Way’s core is warping the general shape of the cluster.  The widest part of the ellipsoid shape runs north to south and is slightly tilted giving it a position angle of 15 degrees.     

To find M19 look approximately 7 degrees due east from the bright star Antares.  Being that M19’s magnitude is around 6.8 it will be visible through binoculars as a nebulous patch of light and will be easily seen as a group of stars through small to moderate sized telescopes.  After observing M19 scan a few more degrees to the southeast and you may notice a patch of sky nearly void of stars.  If you find this you will be looking at what is called the Pipe Nebula.  This is simply clouds of dust obscuring light from stars behind them.  In city skies it will be tough to resolve but look for an area that appears to have no stars at all.

http://messier.seds.org/m/m019.html

http://apod.nasa.gov/apod/ap121123.html

NASA Mission of the Month

Each month we will be celebrating a NASA mission of the month.  This month’s mission is the historic Apollo Program.  The Apollo program was ultimately designed to carry out a program of scientific research relevant to the Moon.  There were a number of unmanned missions and 12 manned missions two of which had accidents.  During Apollo 1 a cabin fire in the crew capsule killed all three astronauts aboard and during Apollo 13 an explosion occurred that kept the crew from landing on the Moon.  After the last Moon landing in 1972 the Apollo spacecraft and Saturn V launch vehicle were used for three Skylab space station missions.  To learn more about the Apollo program visit http://www-pao.ksc.nasa.gov/history/apollo/apollo.htm

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, August 2, 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 August 2, join us indoors in our Planetarium Theater for the ”Update From Mars” with Dr. Ray Arvidson, Director of the Earth and Planetary Remote Sensing Laboratory at Washington University.

This free, indoor lecture will begin at 7 p.m. and seating is limited.  Doors open 15 minutes before show time.  Sorry, no late admissions due to safety issues in the darkened theater.  Please note there is no “Sky Tonight” Presentation for the August 2 First Friday.  There will be a Laserium show starting at 8:30 p.m.

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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