Week of June 17, 2013

This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Monday, June 17.  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, July 5, 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 5:36 a.m. on Monday, June 17 and sunset is at 8:28 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 10:26 p.m. this week.  For those with a sun dial, solar transit or local noon occurs around 1:02 p.m. this week. 

Summer begins this week on June 21 as we reach the summer solstice.  This is the longest day of the year for us in the northern hemisphere as it is when the North Pole is at its greatest inclination towards the Sun (23 degrees and 26 minutes).  You can celebrate this day by going outside at noon and local noon (1:03 p.m. on the 21st) and mark the top of a shadow being cast by a pole such as a lamp post, flag pole or a pole you put in the ground yourself.  The pole acts as a gnomon and can be used to keep seasonal and daily time by tracking the changing shadow.  Marking the shadow at both noon and local noon will show that the further west you are from the meridian the later noon actually happens.  We use the term local noon to describe when the Sun is overhead from your viewing location.  If you mark the noon (not local noon) shadow for each day, week or month (depends on how accurate you want to be) you will create an analemma display for the Sun.  Analemma is a figure eight shape that is created due to the observer’s latitude and something called the equation of time.  To learn more about analemma visit http://en.wikipedia.org/wiki/Analemma

Moonrise for Monday, June 17 is at 2:10 p.m. and moonset is at 1:41 a.m. on the following day.  On Monday, June 17 the Moon will be exhibiting a waxing gibbous phase with roughly 60% of the lunar disk illuminated.  Full moon occurs on June 23.  June’s full moon occurs as the Moon reaches it closest point to the Earth called perigee.  When this happens the often over hyped phenomena called Supermoon occurs.  This close approach happens each month it just normally doesn’t line up this close to full moon.  On this night the Moon will appear about 7% larger.

International Space Station (ISS) Observing

ISS passes over St. Louis for the next two weeks starting Monday, June 17 are all late evening passes.  The best passes are on the evenings of June 19, 20, 22 and 23.  For more information check the table below.

Catch ISS flying over St. Louis in the morning hours the week of Monday, June 17. 

Date

Mag

Starts

Max. altitude

Ends

Time

Alt.

Az.

Time

Alt.

Az.

Time

Alt.

Az.

17 Jun

-0.4

21:14:26

10

N

21:15:28

11

NNE

21:16:30

10

NNE

17 Jun

-2.2

22:49:48

10

NW

22:52:54

37

NNE

22:53:06

37

NE

18 Jun

-1.4

22:00:51

10

NNW

22:03:37

24

NNE

22:05:34

15

ENE

18 Jun

-0.9

23:37:17

10

WNW

23:38:24

19

WNW

23:38:24

19

WNW

19 Jun

-0.9

21:11:58

10

NNW

21:14:15

17

NNE

21:16:31

10

ENE

19 Jun

-3.1

22:47:59

10

NW

22:50:55

67

W

22:50:55

67

W

20 Jun

-2.9

21:58:49

10

NW

22:02:04

56

NE

22:03:28

29

ESE

21 Jun

-2.0

21:09:46

10

NW

21:12:47

33

NNE

21:15:48

10

E

21 Jun

-1.6

22:46:37

10

WNW

22:48:54

24

WSW

22:48:54

24

WSW

22 Jun

-2.7

21:57:05

10

WNW

22:00:15

47

SW

22:01:32

29

SSE

23 Jun

-3.3

21:07:47

10

NW

21:11:04

89

NE

21:14:13

11

SE

24 Jun

-1.0

21:56:06

10

W

21:58:12

16

SW

21:59:48

12

SSW

25 Jun

-1.8

21:06:12

10

WNW

21:09:05

29

SW

21:11:58

10

SSE

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

The elusive planet Mercury is once again with us in the early evening.  You only have a short time to catch this planet as it sets at 9:58 p.m.  Through a telescope you will see Mercury in a crescent phase owing to the fact that it is closer to the Sun then we are. 

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 Taurus and will set by 9:56 p.m. 

Saturn

Look for the ringed planet shortly after sunset in the southern skies.  Currently Saturn is found in the constellation Virgo just to the east of the bright star Spica.  Saturn will set by 2:57 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 Scorpius.  This is a prominent summer constellation that is rising by 9 p.m. and is above the horizon around 11 p.m.  Why focus on a something that becomes visible so late?  Unfortunately due to the growing daylight and twilight hours, we do not have dark skies until after 10 p.m.

Scorpius is one of the twelve zodiacal constellations.  Zodiac constellations were created by ancient astronomers to track the movement of stars that appeared to wander amongst the other stars.  They noticed that the wandering stars always followed a specific path in the sky.  Today we call this the ecliptic and the wandering stars we now know as planets.  Also found along the ecliptic are the Sun and Moon meaning that Scorpius and the other zodiac constellations are visible anywhere on the Earth.     

The name Scorpius comes from the ancient Greeks who saw this as the giant scorpion that killed the great hunter Orion.  Owing to the fact that Scorpius is visible around the world, there are numerous other interpretations for this grouping of stars.  One of my favorites comes from ancient Polynesia in which many of the ancient islanders believed this was the giant fishhook the Sky Father plunged into the oceans to pull up the islands. 

To find Scorpius look almost due south after 11:00 p.m. and you will find a large and bright fishhook shape of stars.  The first star in Scorpius you see through the veil of twilight is the red supergiant Antares.  Many people see this as the heart of the scorpion and it is our first stop in Scorpius. 

http://www.iau.org/static/public/constellations/pdf/SCO.pdf    

Object of the week for June 3 is the bright star Antares.  Also known as Alpha Scorpii, this is the brightest star in Scorpius and the 15th brightest in the sky.  It is unmistakable as it has a distinct reddish orange color.  The reddish color indicates the star is a red supergiant nearing the end of its stellar life.  In optical light Antares is 10,000 times brighter then the Sun.  Due to a cool surface temperature of 3600 Kelvin, Antares radiates a great deal of light in the infrared wavelength.  If you account for this, Antares is a whopping 60,000 times brighter then the Sun.  Antares lies approximately 550 light years away, is 15 to 18 times more massive than the Sun and has a radius of 3.4 AU (one AU = 93 million miles; average distance between Sun and Earth).  Due to its high mass, Antares will likely develop an iron core that will lead to a violent core collapse resulting in an explosion called a type II supernova

Antares is also a double and a variable star.  Both features will be difficult to observe but are worth looking in to.  Antares is a semi-regular variable that only changes by a few tenths of a magnitude.  The companion to Antares a hot B-class star called Antares B which lays only 550 AU away.  At this distance, Antares B is fully immersed in the solar wind from Antares.  With an angular distance of less than 3 arc seconds it will require at least a 6-inch telescope to resolve the companion.  If you are successful in splitting the pair you should notice that Antares B has a greenish color that is the result of a color contrast caused by the bright reddish light from Antares.

Object for the week of June 10 is a globular star cluster called M4.  This is one of 156 globular star clusters found in the Milky Way galaxy.  M4 is one of the closest globular clusters to us lying at a distance of roughly 7,200 light years away.  Its age is estimated to be roughly 12.2 billion years old making it one of the oldest structures in the Milky Way.  It orbits the galaxy once every 116 million years passing through the galactic plane from time to time.  Due to tidal forces, this cluster sheds stars each time it passes through the galactic plane.  Currently it has a mass of about 67,000 solar masses which is low compared to other globular clusters.  Using the Hubble Space Telescope scientists have peered into the heart of this globular and found a stellar graveyard.  The center of this cluster has a number of white dwarf stars which are the dense carbon/oxygen cores of low mass stars that at the end of their lives.  It is estimated that M4 has upwards of 40,000 white dwarfs which will likely be used to refine its estimated age.  M4’s Shapley-Sawyer classification is XI indicating it is a loosely concentrated globular star cluster. 

To find M4 look for Antares discussed last week and then scan about 1.4 degrees to the west.  M4 has a magnitude of 5.6 making it just barely visible to the unaided eye if observing from dark locations.  It is an easy find in binoculars and will resolve into individual stars through a 4-inch instrument.  Looking closely you can see a bar-like structure of stars extending through the center of the cluster.  M4 is a fascinating look into the distant past of the Milky Way.  It will be visible all summer long and is a great deep sky object for beginning observers.

http://messier.seds.org/m/m004.html

Object for the Week of June 17 is the open star cluster M7.  This star cluster also known as Ptolemy’s cluster, is roughly 800 light years away and has a mass of roughly 735 solar masses.  To the naked eye M7 appears as a faint patch of nebulous light that was first recorded by Claudius Ptolemy in his treaties on astronomy called the Almagest.  Through binoculars you will start to resolve some of the brightest stars and through a telescope you can count 30 to 80 individual stars.  A number of the stars in M7 are double stars and on the western edge of the cluster there is a much more distant and faint globular cluster called NGC 6453.  Also in the cluster is a planetary nebula called PK356-4.1 but this will require dark skies and a large telescope to see.

M7 is simple to find once Scorpius has fully risen above the horizon.  First look for the tail of the scorpion or barb of the fishhook shape.  The two brightest stars in the barb are Shaula and Lesath.  Once you have found this part of Scorpius look about 4 degrees northeast of Shaula and you will easily see this bright star cluster.  M7 is a great deep sky object for those just starting to explore the sky’s deep sky wonders.

http://messier.seds.org/m/m007.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 Gemini Program.  The Gemini Program lasted from 1962 to 1966; it included 10 manned flights and was the intermediary program between the Mercury and Apollo programs.  The Gemini program was needed so NASA could learn more about long duration space flights and their effects on astronauts; develop rendezvous and docking methods with other orbiting space craft; perfect reentry and landing methods; and learn more about the effects of weightlessness on astronauts and their physiological reactions.  These four Gemini mission objects were crucial for getting astronauts to the Moon and back.  Project Gemini doesn’t always the credit it deserves but without it the Apollo missions would not have happened.  To learn more about Project Gemini visit http://www-pao.ksc.nasa.gov/kscpao/history/gemini/gemini.htm

50th Anniversary of the James S. McDonnell Planetarium

James S. McDonnell Planetarium 50th Anniversary Logo2013 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, July 5, 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 July 5, 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 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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