Week of September 30, 2013

This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Monday, September 30.  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, October 4, 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 6:56 a.m. on Monday, September 30 and sunset is at 6:45 p.m. providing us with roughly 12 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 8:13 p.m. this week.  For those with a sun dial, solar transit or local noon occurs around 12:51 p.m. this week. 

Moonrise for Monday, September 30 is at 2:36 a.m. and moonset is at 4:13 p.m.  The Moon will be exhibiting a waning crescent phase with roughly 19% of the lunar disk illuminated.  New moon occurs on October 5.

International Space Station (ISS) Observing

The next visible passes of ISS over St. Louis are a mixture of morning and evening passes.  The best passes are the passes on the mornings of September 30, October 2, October 3 and the evening pass of October 7.  See the table below for information regarding these passes

Catch ISS flying over St. Louis in the morning hours starting Monday, September 30. 

Date

Mag

Starts

Max. altitude

Ends

Time

Alt.

Az.

Time

Alt.

Az.

Time

Alt.

Az.

1 Oct

-2.0

05:58:12

10

N

05:12:34

37

NNE

05:15:41

10

ESE

2 Oct

-0.1

04:25:37

14

ENE

04:25:37

14

ENE

04:26:21

10

E

2 Oct

-2.7

05:58:32

21

WNW

06:00:21

39

SW

06:03:27

10

SSE

3 Oct

-2.4

05:12:29

42

SE

05:12:29

42

SE

05:14:38

10

SE

4 Oct

-1.2

05:59:31

13

SW

05:59:31

13

SW

06:00:37

10

SSW

6 Oct

-1.2

19:24:39

10

SSE

19:26:03

12

SE

19:26:12

12

SE

7 Oct

-3.0

20:10:06

10

SW

20:12:55

57

SSW

20:12:55

57

SSW

8 Oct

-2.6

19:21:26

10

SSW

19:24:30

35

SE

19:26:31

18

ENE

9 Oct

-2.2

20:08:59

10

WSW

20:12:09

41

NNW

20:12:51

35

N

 

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 Libra and will set by 8:29 p.m. 

Mars

Mars is out of the Sun’s glare and will rise around 3:05 a.m. this week.  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.

Jupiter

The largest planet in our solar system has returned to our skies.  This week it will rise around 12:26 a.m. becoming visible roughly 30 minutes later.  It is currently paired with Mars in the morning skies. 

Saturn

Look for the ringed planet shortly after sunset in the southwest.  Currently Saturn is found in the constellation Libra just to the west of the bright star Zubenelgenubi.  Saturn will set by 8:12 p.m.  .  Take a look at Saturn while you still can.  Soon the ringed planet will lost in the glare of the Sun.

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 October will be Cepheus the King.  In Greek mythology Cepheus is best known as the husband of Cassiopeia and father to Andromeda.  These three are famously part of the story of Perseus.  Cepheus was also one of the Argonauts that sailed with Jason as he quested for the Golden Fleece. 

Usually Cepheus is listed as part of the fall sky but in reality from St. Louis he is visible year round.  Cepheus is part of our circumpolar which means it never rises or sets but rather just circles around the North Star.  If the stars were visible in the daytime, Cepheus would always be visible.  The easiest way to find Cepheus is to star hop from Alpha to Beta Cassiopeiae and keep heading to the north.  Look for an elongated upside down house shape of stars.  The house shape extends almost to the North Star. 

The first object we will cover in Cepheus is the variable star Delta Cephei.  This star is the prototype Cepheid variable.  It is a giant yellow star that due to internal pulsation will flare in brightness then fade back down to its normal magnitude.  The cause of these pulsations is not confirmed but one theory suggests that Cepheids are stars that have an internal struggle between the outward pressure of radiation and the internal pull of gravity.  Due to increasing and decreasing temperatures the balance of these forces ebb and flow causing the star to expand and contact. 

Cepheid variables also have a special place in astronomy as the period of their pulsations is directly related to their absolute brightness which in turn can be used to measure how far away the star is.  This period luminosity relationship was discovered by one of astronomy’s unsung heroes.  Her name was Henrietta Swan Leavitt and she was hired on as a computer at the Harvard College Observatory in 1893.  Regardless of her advanced education Henrietta was held back from academic careers in astronomy as in those days it was primarily seen a male prerogative.  In 1912 she was cataloging variable stars in the Small Magellanic Cloud and found 25 of them to be Cepheids.  When she arranged them in order of periods she discovered that the longer the period was the brighter the star was.  This discovery was one of the most important in modern astronomy.  Using Henrietta’s period luminosity discovery and his discovery of a Cepheid in what was then known as the Andromeda Nebula, Edwin Hubble was able to prove that the Andromeda Nebula could not be a nebula in the Milky Way but instead must be a galaxy beyond ours.  In essence what Henrietta did for astronomy is she gave astronomers the tool that opened the universe to our understanding.  For this critical discovery she received little to no recognition.  So when you look to Delta Cephei this month remember this and think of Henrietta Swan Leavitt and maybe do your part to teach people about this unsung hero of astronomy.

Delta Cephei varies in its brightness over a period of 5.366 days.  It changes from 4.4 magnitude to 3.5 magnitude in about one and half days then fades back to 4.4 magnitude slowly over a period of four days.  Both the maxima and minima are bright enough to be seen without the aid of a telescope or binoculars.  Owing to this and the short time it takes to brighten then fade, Delta Cephei is a great beginning target for those interested in variable star astronomy. 

To find Delta Cephei use Cassiopeia to find the house shape of Cepheus.  Next locate the stars Alpha and Gamma Cephei.  These are the two stars that mark the bottom of the house shape of Cepheus.  If you look closely at Gamma Cephei you will notice it is part of a little triangle shape of stars.  The star that marks the peak of this little triangle shape as it extends away from Cepheus is Delta Cephei.  Use the maps linked below to help you find this gem of the northern skies.  I will also include links to the AAVSO site for further reading about Cepheid variables and Henrietta Swan Leavitt. 

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

http://www.aavso.org/files/vsots/0900.pdf

http://www.aavso.org/henrietta-leavitt-%E2%80%93-celebrating-forgotten-astronomer

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. 

http://www.skyandtelescope.com/observing/highlights/Bright-Nova-in-Delphinus-219631281.html

Update 9/9/2013: Del 2013 is hanging on at a little past 7th magnitude.  Since last week it has faded to 7.3.  On a clear night it can still be spotted through a decent pair of astronomical binoculars.  Follow the link for update information regarding the nova star Del 2013.

http://www.skyandtelescope.com/observing/highlights/Bright-Nova-in-Delphinus-219631281.html

Update 9/16/2013: Del 2013 is hanging on at 7.4 magnitude but unfortunately the bright Moon will be a problem for the next few weeks.  It will still worth trying to catch a glimpse of the fading star but you may have to wait until the end of September when the Moon will no longer be a problem. 

http://www.skyandtelescope.com/observing/highlights/Bright-Nova-in-Delphinus-219631281.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 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.

http://voyager.jpl.nasa.gov/mission/interstellar.html

http://voyager.jpl.nasa.gov/mission/interstellar.html

Voyager 1 Update: It was announced last week that the Voyager 1 space craft, at a distance of roughly 13 billion miles away, has left the solar system.  Voyager 1 will now be exploring the realm of interstellar space.  It has enough fuel to continue to operate until 2020 when scientists will start to shut down various components on the spacecraft.  This marks a new stage in human exploration of space.  To learn more about this monumental accomplishment visit http://www.jpl.nasa.gov/news/news.php?release=2013-278

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, October 4, 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 October 4, join us indoors in our planetarium theater for “The Sky Tonight”.  Showtime is at 7 p.m.  As there is a 7 p.m. star show 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

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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