Week of February 24, 2014

This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Monday, February 24.  All times are given as local St. Louis time (Central Standard 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, March 7, 2014 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 6:40 a.m. on Monday, February 24 and sunset is at 5:49 p.m. providing us with roughly 11 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 7:17 p.m. this week.  For those with a sun dial, solar transit or local noon occurs around 12:14 p.m. this week. 

Moonrise for Monday, February 17 occurs at 2:36 a.m.  Moonset will occur at 12:51 p.m.  On Monday the 24th the Moon will be exhibiting a waning crescent phase with roughly 28% of the lunar disk illuminated.  New moon occurs on March 1st.  

International Space Station (ISS) Observing

The next visible passes of ISS over St. Louis are all evening passes.  The best passes are on the evenings of February 24 and 26.  Learn more about these passes and others this week in the table below.  After this week we will not see ISS again until March 10 when it returns to our morning skies.

Catch ISS flying over St. Louis in the evening hours starting Monday, February 24. 

Date

Mag

Starts

Max. altitude

Ends

Time

Alt.

Az.

Time

Alt.

Az.

Time

Alt.

Az.

24 Feb

-3.4

18:40:19

10

NW

18:43:38

82

NE

18:46:24

14

SE

25 Feb

-0.6

19:28:43

10

W

19:31:00

17

SW

19:33:08

11

S

26 Feb

-1.5

18:39:05

10

WNW

18:42:04

32

SW

18:45:03

10

SSE

28 Feb

 0.1

18:39:14

10

WSW

18:40:11

11

SW

18:41:07

10

SW

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

Venus has started its next morning apparition. It rises around 4:13 a.m. becoming easily visible by 5:00 a.m.  For those awake at this time you will see Venus, Saturn and Mars stretching across the southern skies.  This planetary display nicely represents the path that the planets, Sun and Moon follow.  This path is called the ecliptic.

Mars

Mars is now in the constellation Virgo and will rise around 9:52 p.m. this week.  For those awake around 11:30 p.m. look to the east and you will see a reddish-orange object low in the eastern skies.  Mars will be seen earlier each week 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

Jupiter is now rising as the Sun is setting.  For those with a clear eastern horizon look east roughly 30 minutes after sunset and you should see Jupiter shining brighter than any star in the sky.  As twilight fades you will see the bright stars Castor and Pollux just north of Jupiter.  Looking at these stars and then comparing them to Jupiter you will see that the stars are twinkling and Jupiter is not.  The twinkling you see is called scintillation which is a distortion of the stars light by Earth’s atmosphere.  Testing for scintillation is how you can distinguish stars from planets. 

Saturn

Saturn is now out of the glare of the Sun.  It rises by 12:00 a.m. and will be an easy target by 1:00 a.m.  Saturn is currently in the constellation Libra.  It forms a nice triangle in the sky with Libra’s two brightest stars Zubenelgenubi and Zubeneschamali.

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. 

For February the constellation we will highlight is Auriga the Charioteer.  Auriga is the northern most constellation in the asterism known as the Winter Triangle.  The brightest star in Auriga is Capella which is the 6th brightest star in the sky.  This time of the year Auriga has already begun to rise once the Sun has set and will be visible shifting from east to west.  Look for a home plate shaped grouping of stars north of Orion.

One story in Greek myth had Auriga representing Erichthoneus the lame son of Hephaestus and the Mother Earth.  It was believed the Erichthoneus invented the four horse chariot so he could get around easier.  Zeus admired Erichthoneus for his ingenuity and placed him in the heavens for eternity.    

The first object we will explore in Auriga is the open star cluster M37.  This is an open cluster that lies about 4,400 light years away containing roughly 500 stars that are about 300 million years old.  M37 has a Trumpler classification of I,1,r.  This is as good as it gets as this classification means M37 is a (I) bright detached globe of stars, (1) has numerous bright members and (r) has a rich field of stars. 

To find M37 look north of Orion for Auriga’s home plate shape of stars.  Once you can find this look between the two stars Beta Taurii and Theta Aurgae.  Grab a pair of binoculars and look about halfway between these two stars.  Just east of this midpoint you will see a faint cotton ball shaped source of light; this is M37.  Through a telescope you can start to resolve the 150 or so stars that are 12th magnitude or brighter.  With an age of 300 million years there are roughly 12 red giant stars in the cluster that have evolved off the their main sequence.  See if you can spot any of them

M37 is the brightest of a trio of star clusters that span across the southeast corner of Auriga.  The next few weeks we will cover the other two of the great open clusters in Auriga.  All three are great binocular targets.  For help finding M37 follow the link below.

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

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

http://messier.seds.org/m/m037.html

The object for the week of February 10 is the open cluster M36.  Like last week’s star cluster M37, M36 is an open star cluster that lies roughly 4,100 light years away.  It has 60 stars that are proven to be members of this cluster which have an age of 25 million years.  Unlike M37, M36 has no red giant stars.  At 6.3 magnitude M36 is an easy target in binoculars and small telescopes will be able resolve a few of the brightest members.    

To find M36 look north of Orion for Auriga’s home plate shape of stars.  Once you can find this look between the two stars Beta Taurii and Theta Aurgae.  M36 will be about half way between and just a little to the right of these two bright stars.  It will not be quite as obvious as last week’s star cluster but with a Trumpler classification of I,3,r it will still be an easy find.  Follow the links below to find out more about this star cluster.

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

http://messier.seds.org/m/m036.html

The object for the week of February 17 is the open star cluster M38.  M38 is the last of three star clusters in Auriga that we will cover.  M38 lies at a distance of roughly 4,200 light years away and its stars are estimated to be about 220 million years old.  The brightest star in the cluster is a 7.9 magnitude yellow giant star that is about 900 times more luminous than the Sun.  This will be the toughest of the three to see as it has a Trumpler classification of II,2,r.  M38 has a visual magnitude of 7.4 making it an easy target for those with binoculars.  Instead of the fuzzy ball shape of light you see with M37 and M36 you will see what some say looks like the Greek letter Pi or some say it looks like an oblique cross. 

To find M38 look north of Orion for Auriga’s home plate shape of stars.  Once you can find this look between the two stars Beta Taurii and Capella.  Grab a pair of binoculars and look about halfway between these two bright stars.  Again you will see a few lines of stars that look like an oblique cross shape.  For more information about M38 follow the links below.

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

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

http://messier.seds.org/m/m038.html

The final object we will cover in Auriga is the runaway star AE Aurigae.  This 6th magnitude star lies at a distance of roughly 1,400 light years.  It is a hot luminous blue O-class star with a temperature of 31,000 kelvins.  It is has 17 times the mass of the Sun, It is roughly 33,000 times more luminous than the Sun and it is 6.3 times larger than the Sun.  AE Aurigae is also an Orion type variable star.  It varies between 5.4 and 6.1 magnitudes however these changes are not frequent and are not periodic.  Orion variables are eruptive variables that will often show significant increases in brightness and then stay there for long periods of time.  They are also normally associated with clouds of dust and gas that are not usually related to the star.  AE Aurigae does have an unrelated nebula that we see because the light and solar wind from AE Aurigae is interacting with the nebula.  The nebula is called IC 405 also known as the Flaming Star Nebula.     

Considering just this information, AE Aurigae already appears to be an impressive and interesting star.  Yet it is for another reason that many astronomers are interested in tracking down this star that hovers on the edge of naked eye visibility.  AE Aurigae is what is called a runaway star.  These are stars that have abnormally high velocities and are moving away from stellar associations.  AE Aurigae is moving away from an area near the OB1c association of stars in Orion’s Sword. 

Runaway stars are generated due to some kind of enormous energy release.  The two events thought to be able to eject stars like this are supernovas and colliding binary stars.  Both methods have been suggested as the process that ejected AE Aurigae but these days most agree that a collision between two multiple star systems about 2 million years ago ejected AE Aurigae and two other famous runaways Mu Columbae and 53 Ariets from the area around the quadruple star system Iota Orionis.  Iota Orionis has four member stars.  Three of these stars have similar ages indicating that they formed from the same material.  The fourth which forms a tight spectroscopic binary with the brightest of the four stars is about twice the age of the other stars in the system.  Due to this it is believed that a collision of two multiple star system occurred forming a new system we see as the Iota Orionis system and ejected members from the two original systems.  AE Aurigae is one of the ejected stars. 

To find AE Aurigae look north of Orion for Auriga’s home plate shape of stars.  Once you can find this look between the two stars Alnath in Taurus (Beta Taurii) and Iota Aurigae.  About halfway between these stars look a few degrees north and you will find a vertical line of 5th magnitude stars.  Starting from the south end of the line they are 14,16, IQ and 19 Aurigae.  About one degree west of these stars is AE Aurigae. 

AE Auarigae can be challenging to identify if you do not have a star chart with enough detail.  Below you will find a number of charts with varying degrees of detail.  All of them will have AE Aurigae on them but unfortunately it will not be labeled.  Start with the IAU charts for Auriga and Taurus.  On these maps you will see the two guide stars Beta Taurii and Iota Aurigae.  Also on the IAU map of Auriga you will find the Flaming Star Nebulae that is associated with AE Aurigae labeled as IC 405.  I will also include the IAU map for Orion for those that want to see where in the sky AE Aurigae came from.  These maps should be good enough to get you to AE Aurigae but if you want to make sure you have found the right star I have also include charts from AAVSO.  These offer star fields with greater detail but they can be confusing as they indicate AE Aurigae with a cross hair and do the same for other variable stars in the vicinity.  AE Aurigae will be the unlabeled crosshair in the middle of the map.  I will link them in an order so that they progressively show larger fields of view.  The other tool I would recommend you get is the free planetarium software Stellarium.  Once you establish your viewing location you can set the time and date and then just search for AE Aurigae.  This software will show you exactly where it is in the sky.  I will include a link to the Stellarium software below.

Since AE Aurigae sits around 6th magnitude you will need to let your eyes adjust to the darkness for a few minutes.  Grab a pair of binoculars and you should have no problem finding this star even in the light polluted skies of St. Louis.  I like including observing projects like this to introduce viewers to the other gems that sky has to offer.  In 2014 I will try and include a star of interest to every month’s highlighted constellation.  Not all will be runaway stars but they will all be stars of interest.  When you are looking for a change of pace or you just want something other than deep sky objects or planets to look at, the individual stars are always fascinating to explore.             

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

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

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

http://www.aavso.org/vsp/chart

http://www.aavso.org/vsp/chart

http://www.aavso.org/vsp/chart

http://www.stellarium.org/         

Our next Star Party will be held on Friday, March 7, 2014, 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 7:00 p.m.  Regardless of the weather on March 7, join us indoors in our planetarium theater for “The Sky Tonight”.  Showtime is at 7 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

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