Week of April 22, 2013

This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Monday, April 22.  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, May 3, 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 6:15 a.m. on Monday, April 22 and sunset is at 7:45 p.m. providing us with over 13 hours of daylight.  Even after sunset, the light from the Sun will still illuminate our sky just over 1.5 hours.  This period of time is called twilight, which ends around 9:22 p.m. this week.  For those with a sun dial, solar transit or local noon occurs around 12:59 p.m. this week.

Moonrise for Monday, April 22 is at 4:35 p.m. and moonset is at 4:40 a.m. on the following day.  On Monday, April 15 the Moon will be exhibiting a waxing gibbous phase with roughly 88% of the lunar disk illuminated.  Full moon occurs on Thursday, April 25.  April’s full moon is known as the Full Pink Moon.  

International Space Station (ISS) Observing

Visible passes of ISS over St. Louis for the next two weeks starting the week of Monday, April 22 are all evening passes.  For this two week period the best passes occur the evenings of April 22 and 25.  For more detailed information regarding these and other passes click the red links in the table.

Catch ISS flying over St. Louis in the morning hours during the week of Monday, April 22.

Date

 

Mag

Starts

Max. Altitude

Ends

Time

Alt.

Az.

Time

Alt.

Az.

Time

Alt.

Az.

22 Apr

-3.2

21:33:32

10

NW

21:36:37

69

N

21:36:37

69

N

23 Apr

-2.5

20:43:00

10

NW

20:46:07

39

NNE

20:48:03

19

E

23 Apr

-0.4

22:20:03

10

W

22:20:49

14

W

22:20:49

14

W

24 Apr

-2.4

21:28:55

10

WNW

21:31:59

38

SW

21:32:18

37

SSW

25 Apr

-3.3

20:38:05

10

NW

20:41:22

78

SW

20:43:49

16

SE

26 Apr

-0.8

21:25:06

10

W

21:26:54

14

SW

21:28:10

12

SSW

27 Apr

-1.5

20:33:33

10

WNW

20:36:22

26

SW

20:39:10

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

Jupiter

The planet Jupiter will be visible shortly after sunset and sets around 11:10 p.m.  Grab a pair of binoculars and see how many of the Galilean moons you can see.  Depending on when you look you should be able to see all four; Io, Europa, Ganymede and Callisto.  As you watch them sketch their locations relative to Jupiter and you will be following in the footsteps of Galileo.  While looking at Jupiter see if you can spot the stars Kappa and Upsilon Tauri just to the right of the planet.  Both of these stars are multiple star systems with Kappa being two stars and Upsilon being three.  Both systems are members of the V-shaped star cluster called the Hyades just below Jupiter.    

Saturn

Look for the ringed planet shortly after it rises around 8:02 p.m. this week.  Currently Saturn is found in the constellation Libra just to the west of the bright stars Zubeneschamali and Zubenalgenubi.  Opposition for Saturn occurs on April 28, 2013.  As we approach this date Saturn will continue to brighten and be seen early each night.  Once opposition occurs Saturn will be visible shortly after sunset.

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 Cancer the Crab.  Cancer is one of the 12 zodiacal constellations meaning that Sun, Moon and planets can be found in Caner from time to time.  It is located in the spring seasonal sky between the constellations of Gemini and Leo.  Cancer is significantly fainter then its neighbors and may be difficult to spot in light polluted conditions.   To locate Cancer either find Gemini to the upper left of Orion or Leo just below the Big Dipper’s bowl.  Cancer is west of Leo and east of Gemini.  The brightest stars in Caner form a faint upside down Y-shape.  The brightest stars are Acubens, Altarf, Asellus Borealis, Asellus Australis, ζ Cnc, ι Cnc and 55 Cnc. http://iau.org/static/public/constellations/pdf/CNC.pdf

In Greek mythology, Cancer was the giant crab that nipped at the feet of Hercules as he battled Hydra.  In ancient Egypt, Cancer was seen as the lowly scarab which was the representation of the dawn Sun-God Khephri.  It was also a symbol of fertility.

The object for the week of April 1 is Cancer’s brightest and most well known deep sky object known as M44.  Also known as the Beehive cluster or the Praesepe Cluster, M44 is an open cluster containing 350 stars shining with a combined magnitude of 3.7.  At this magnitude, M44 is visible to the unaided eye as a faint patch of nebulous light using averted vision.  Through binoculars you can easily count over 40 stars and with a large telescope roughly 200 can be seen.  The stars in this cluster are approximately 730 million years old and are 577 light years away.   

To find M44 look for the star Asellus Australlis at the branch of the upside down Y-shape described above.  From that star look approximately two degrees to the north and west and you will find M44.

http://iau.org/static/public/constellations/pdf/CNC.pdf

http://messier.seds.org/m/m044.html

The object for the week of April 8 is the open star cluster M67.  Discovered in the late 1700’s, this cluster stands as one of the oldest open clusters in the Milky Way.  Previous open clusters discussed in the night sky update have been hundreds of million years old whereas M67 is has been estimated to be 3.2 to 4 billion years old.  Open clusters normally do not last this long due to gravitational encounters that strip members from the cluster as it moves through the Milky Way.  M67 is also relatively close at a distance of 2,700 light years making it an ideal target to study the evolution of stars.  Being so close to us, our view of M67 is mostly unobstructed by the clouds of soot and dust that permeate the Milky Way.  So the light we see from these stars has gone through very little change or filtering as it travels to us.  In M67 there are nearly 200 white dwarfs, main sequence stars of all types and a number of aging giant stars.  With this spread scientists have clear views of nearly all types of stars in various evolutionary stages. 

To find M67 look for the upside down Y-shape of Cancer.  The bottom left star of the Y-shape is Acubens.  From there look about 1.5 degrees to the west and you will find M67.  With an apparent magnitude of 6.1, M67 is an easy target for binoculars.  City lights will make things much more difficult but it should be visible.  Through a telescope stars in M67 can be resolved with a faint patch of nebulous light in the background.    

http://iau.org/static/public/constellations/pdf/CNC.pdf

http://messier.seds.org/m/m067.html

The object for the week of April 15 is a star called Zeta Cancri or Tegmeni. Zeta Cnc appears as a 5.1 magnitude star about 7 degrees west of the star Delta Cancri.  Zeta Cnc is a multiple star system that was discovered to be a triple system by Sir William Herschel and recently has been determined to be a quadruple star system.  Using a small telescope at high magnification component stars Zeta Cnc A, B and C can be resolved.  Unfortunately the fourth orbits Zeta Cnc C to close to be resolved in backyard instruments.  Zeta Cnc component stars A and B orbit each other quite fast completing one orbit every 59.6 years.  This will be a challenging multiple system to split but will be well worth the effort to see these three golden gems.  A finder chart can be found below.

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

Our final object for the month of April is a star named X Cancri.  Much like the two red variable stars we covered last week in Hydra, X Cancri is a long period variable star with a deep red color.  The deep red color is due to the star having a higher amount of carbon in its atmosphere than oxygen.  This abundance of carbon causes the star to have a sooty atmosphere leading to the distinct reddish hue.  Due to the abundance of carbon in its atmosphere, X Cancri is also called a carbon star.  Carbon stars that are long period variables will often display a spectral change during their maxima and minima.  During their maxima (maximum brightness) the star can have a yellow or orange appearance.  During their minima (minimum brightness) the star will become a dark orange or red color.  X Cancri has a magnitude range of 5.6 – 6.9 and a period of ~180 days.  Current observations list X Cancri with a magnitude of 6.2. 

To find X Cancri look for the star Asellus Australis located at the crook of the upside down Y-shape.  Look about 3 to 4 degrees east of Asellus Australis and 1 to 2 degrees north of the double star Omicron Cancri.  You will need binoculars to see X Cancri.  Bellow there will be two links for star charts marking all named stars.  Use the first link to find the guide stars then the second one to find X Cancri. 

http://iau.org/static/public/constellations/pdf/CNC.pdf

http://www.aavso.org/vsp/chart/pl/1115eeq

NASA Mission of the Month

Each month we will be celebrating a NASA mission of the month.  This month’s mission is the Hubble Space Telescope.  This telescope is named after the famous astronomer Edwin Hubble who showed us that the universe was huge and was expanding at exceeding rates.  This discovery revolutionized astronomy.  Much like the astronomer, the telescope continues to push our understanding of the universe and allows astronomers to see some of the most distant objects ever observed.  The Hubble Space Telescope has been in space now for over 20 years and has made over 1 million observations.  It continues to shed light on the universe and its origin.  To learn more about the Hubble Space Telescope visit

http://hubblesite.org/

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 the Planetarium page.

Our next Star Party will be held on Friday, May 3, 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 May 3, 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 shows 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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