Week of December 23, 2013

This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of December 23.  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, January 3, 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 7:16 a.m. on Monday, December 23 and sunset is at 4:44 p.m. providing us with less than 10 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 6:20 p.m. this week.  For those with a sun dial, solar transit or local noon occurs around 12:00 a.m. this week. 

Moonrise for Monday, December 23 occurs at 10:51 p.m.  Moonset will occur at 11:15 a.m. on the following day.  On Monday the 23rd the Moon will be exhibiting a waning gibbous phase with roughly 68% of the lunar disk illuminated.  Last quarter moon occurs on Wednesday, December 25. 

 

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 December 26, 27, 28 and 29.  Learn more about the passes and others this week in the table below.

Catch ISS flying over St. Louis in the evening hours starting Monday, December 23. 

Date

Mag

Starts

Max. altitude

Ends

Time

Alt.

Az.

Time

Alt.

Az.

Time

Alt.

Az.

23 Dec

-1.0

17:26:38

10

N

17:27:53

12

NNE

17:29:08

10

NE

23 Dec

-0.2

19:02:12

10

NW

19:02:18

11

NW

19:02:18

11

NW

24 Dec

-1.8

18:13:58

10

NNW

18:16:11

24

N

18:16:11

24

N

25 Dec

-1.5

17:25:46

10

NNW

17:28:11

18

NNE

17:30:11

12

ENE

25 Dec

-0.9

19:01:54

10

NW

19:03:08

21

WNW

19:03:08

21

WNW

26 Dec

-3.3

18:13:26

10

NW

18:16:45

60

NE

18:17:52

49

E

27 Dec

-2.6

17:25:02

10

NW

17:28:10

36

NNE

17:31:18

10

E

27 Dec

-1.0

19:02:02

10

WNW

19:04:46

23

SW

19:04:52

23

SW

28 Dec

-2.1

18:13:08

10

WNW

18:16:20

43

SW

18:19:31

10

SSE

29 Dec

-3.2

17:24:26

10

NW

17:27:48

82

SW

17:31:08

10

SE

30 Dec

 0.0

18:13:39

10

W

18:15:34

14

SW

18:17:28

10

SSW

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 20 minutes after sunset.  Venus will be low to the horizon and any trees or buildings southwest of you may obscure it from view.  Venus is currently seen in the constellation Sagittarius and will set by 6:46 p.m.  If you have binoculars at home you should notice that Venus in a crescent phase.  Due to Venus being closer to the Sun it is always in a phase similar to those we see the Moon exhibit.  The difference is Venus is always closer to the Sun so we never see a full Venus.  As Venus approaches its inferior conjunction in January next year, Venus will exhibit a thinner and thinner crescent shape.    

Mars

Mars is now in the constellation Virgo and will rise around 12:27 a.m. this week.  For those awake around 2:00 a.m. look to the east and you will see a reddish-orange object high 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

The largest planet in our solar system has returned to our evening skies.  This week it will rise around 5 :46 p.m. becoming visible roughly 30 minutes later.  Just above and to the east of Jupiter you will see the 1st magnitude stars Castor and Pollux.  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 rise by 3:53 a.m.  and will be an easy target by 4:30 a.m.  Morning twilight will still be a small problem and trees and buildings will continue to obscure our views.  For those that can find a clear eastern horizon you should be able to spot Saturn by about 5:00 a.m.  Binoculars will help but as the month goes Saturn will become easier to see.

 

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 December we will be doing things a little different.  Instead of highlighting a constellation for December we will be tracking down some of the closest stars to the Sun.   Observing projects like this are a good way to refine your observing skills.  They also serve as a nice alternative for when you want something more than the same old faint fuzzies you have been looking at for the last few months.  All of the stars chosen for this month will be visible in binoculars and some will be visible to the naked eye. 

Week one of our expedition through our stellar neighborhood will bring us to two of the closest and brightest stars in the sky; Sirius and Procyon.  These two stars are found in the winter circle and will be visible by 10:00 p.m. 

Sirius is the brightest star in the night sky shinning at magnitude -1.74 and it is the 6th closest to the Sun.  It is a white A-Class hydrogen fusing star.  It has a smaller and hotter companion known as Sirius B that has evolved into a white dwarf star at the end of it existence.  Sirius B is the remnant core of a more massive star that was likely 5 to 7 times more massive than the Sun.  All that remains of Sirius B is a dense hot core of carbon and oxygen.  This dense core is only 0.92 times the size of Earth and shines with a luminosity of 2.8 percent of the Sun’s total output.  Sirius B is very difficult to see due to the intensely bright glare of its partner Sirius A. 

Procyon is the 8th brightest star in the night sky shining at a magnitude of 0.34 and it is the 15th closest star to the Sun.  Like Sirius, Procyon is a binary system with the main component star (A) being a hot white F-Class star and the secondary star (B) is a white dwarf star at the end of its life.  Both of the white dwarfs discussed in this section are two of three white dwarfs that helped identify and understand what white dwarfs actually are.

To find both Sirius and Procyon, look for Orion the Hunter and his famous three belt stars.  Once you have found the belt follow the three stars to the left of the belt and the brightest star you see will be Sirius.  Looking east of the belt will bring you to Procyon in Canis Minor.  Both of the stars are members of what many observers call the Winter Circle.  This is a group of stars that circles Orion and helps identify most of the winter constellations.  For those just beginning with backyard astronomy this structure is in my opinion the best place to start.  Use the maps below to help identify the star Sirius and Procyon. 

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

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

For the week of December 9 we will visit the 10th nearest star, Epsilon Eridani.  It is a K2-Class orange star that currently is in its main sequence.  The temperature of this star is roughly 5,000 K making it just a bit cooler than the Sun.  Epsilon Eridani is not much smaller than the Sun but it only shines with about 35% the luminosity of the Sun.  At that luminosity and a distance of 10.5 light years, Epsilon Eridani appears as a 3.73 magnitude star in our southern skies. 

Epsilon Eridani has been the focus of a number of studies.  Since the 1930’s this star was believed to either have a companion or to be a potential candidate for a nearby star that has a planet.  The companion theory was disproven but in 1985 a circumstellar debris disc was discovered.  Observations of this dusty debris ring showed evidence of clumping that was suggestive of a large body orbiting the star.  Since the 1980s radiometric observations were been done that indicated there was a large body perturbing Epsilon Eridani.  From 2001 to 2003 the Hubble Space Telescope joined the hunt and confirmed that there is indeed a planet orbiting Epsilon Eridani.

The SETI program also considered Epsilon Eridani a star of interest.  The SETI program or the Search for Extraterrestrial Intelligence included Epsilon Eridani as a target for their radio telescopes hoping to find signals that would indicate an advanced civilization may live on a planet orbiting the star.  No such signal has been found yet but SETI is still strong and actively searching the skies for the signal that most want to believe is out there. 

Epsilon Eridani has also been the focus of a number of studies interested in developing alternative propulsion methods with the hopes of sending a ship to a nearby star.  Current methods of propulsion cannot provide the thrust needed to get a spacecraft to a nearby star in a human lifetime.  For decades now scientists have been looking into new methods to get us to stars like Epsilon Eridani.  The Deadelus and Icarus programs included Epsilon Eridani as a target star that could be reached using one of their alternative methods.  Various designs including nuclear fusion, fission and laser propulsion have been suggested to get a spacecraft to Epsilon Eridani within a human lifetime.  These ship designs are purely theoretical but still remain as likely ways humanity will be able to visit our stellar neighbors in the future.

Epsilon Eridani is found in the constellation Eridanis the River.  This constellation starts at the celestial equator and heads south out of view from us here in St. Louis.  The part of Eridanis we can see is found just south and west of the constellation Orion.  Finding Epsilon Eridani starts with finding the bright stars Saiph and Rigel at the bottom of Orion.  Draw a line extending from Saiph to Rigel and follow that line roughly 20 degrees to the west.  Doing this you will see four stars ranging in brightness from 2nd to 3rd magnitude.  These four stars form a crooked line of stars and the west most of these stars is Epsilon Eridani.  Use the maps linked below to find the guides stars and Epsilon Eridani.  There will also be links to the relevant programs discussed above.

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

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

http://www.seti.org/

http://planetary.org/    

 

For the week of December 16 we will visit 61 Cygni, the 16th closest star to the Sun.  Let’s start with the fact that 61 Cygni is not one but two stars.  The stars in this binary system take 659 years to orbit each other and are 44 to 124 AU (1 AU = 93,000,000 miles) apart depending on where they are in their orbits.  Together they appear as one star to the naked eye making them the 4th closest star visible without the aid of a telescope or pair of binoculars. However, using a pair of binoculars will split 61 Cygni into its two component stars.  The three naked eye stars that are closer are those discussed in the previous weeks.  61 Cygni A and B are both Orange K-Class stars that are smaller, cooler and older then the Sun.

The 61 Cygni system has also been dubbed Piazzi’s Flying Star due to its large proper motion in the sky.  Careful observations of this star through an entire year will reveal that this pair of stars is moving through the sky.  Even though all stars are moving most are far enough away that detection of their proper motion is not possible through backyard instruments.  Stars like 61 Cygni that have high proper motions and are close to us allow us to monitor their movement through the Milky Way by carefully monitoring them in respect to the background star fields.    

To find 61 Cygni first locate the Summer Triangle.  The three stars that make the Summer Triangle are Deneb, Vega and Altair.  These bright stars can be seen in the western skies about 40 minutes after sunset.  Once you can see the triangle focus on the star Deneb.  This is the tail star of Cygnus the Swan and will be your starting point for finding 61 Cygni.  From Denib start scanning to the east and you will see two pairs of stars within 10 degrees of Deneb.  The first pair stars are the Xi and Nu Cygni and the second pair is Sigma and Tau Cygni.  These four stars range in brightness from 3.5 to 4.5 magnitude and should be visible to the unaided eye.  West of Sigma and Tau Cygni using binoculars you will see a fainter pair of stars.  The northern star of this pair is 61 Cygni.  Even though the directions sound complicated, finding 61 Cygni is not very difficult.  The key is to use a good map of the sky.  61 Cygni is visible to the unaided eye but in light polluted areas you will be better off using a pair of binoculars.

http://upload.wikimedia.org/wikipedia/commons/2/21/61_cygni_map.png

 

The star we will explore for the week of December 23 is Lalande 21185.  This is the 5th nearest star to the Sun and is our first Red Dwarf star we will talk about this month.  Red dwarf stars are of particular interest for many reasons.  One being they are the most abundant type of star in our galaxy.  In the Sun’s vicinity 20 of the 30 nearest stars are red dwarfs.  Also of interest is their longevity.  Of all the hydrogen fusing stars, red dwarfs will stay on the main sequence longer than any other star.  The main sequence for red dwarfs can last for trillions of years depending on their mass.  In fact there is no known red dwarf in an advanced evolutionary stage.  Their longevity is owed to how red dwarfs give off their energy.  Stars like the Sun are hot enough inside that the energy given off first travels outward through radiative pressure.  It is so hot that it all radiates out until it reaches an area that is cool enough for convection to take over.  Stars that behave like this see the helium that is synthesized through hydrogen fusion build up in its core.  Eventually core collapse occurs until helium begins to fuse.  In red dwarfs from core to surface, energy transfer is done through convection.  Because of this the helium product from hydrogen fusion does not build up in the core and the star will be able to fuse hydrogen longer.

Lalande 21185 is a red dwarf star that has 0.46 solar masses and is about 40% the size of the Sun.  It is a much smaller and cooler star that shines with only 0.025 solar luminosities.  Most of the energy from this star radiates out as infrared radiation.  At a distance of 8.31 light years this star shines at roughly 7.5 magnitude making it a star that you need binoculars to see. 

To find Lalande 21185 first locate the Big Dipper.  This will be climbing high in the eastern skies by 10 p.m.  Next locate the back two stars in the bowl of the Big Dipper named Delta and Gamma Ursa Majoris.  Follow a line between these stars extending below the bowl about 10 degrees and you will find the star Psi Ursa Majoris.  Continuing in the same direction another 10 degrees will bring you to two more bright stars named Alula Borealis and Alula Australis.  From here you will need to grab a pair of binoculars.  Looking about 5 degrees north of lour last pair of stars you will see a tight grouping of three stars.  The brightest of these three is the star 46 Leo Minoris.  From here look a little under 5 degrees to the east and you will see two stars.  The fainter of the two is Lalande 21185.

This will be the toughest of the stars we look for this month.  As you can see by the directions above, Lalande 21185 will push your star hopping ability.  If you are using binoculars most will have a 5 to 7 degree field of view.  So each star hop listed above will be just within or just beyond one binocular field of view.  Below you will find IAU maps for the constellations Ursa Major and Leo Minor.  These maps will get you up to the last star hop to Lalande 21185.  To pinpoint Lalande 21185 I would recommend you download the Stellarium software.  This is a free desktop planetarium software that will be a great aid in this month’s featured stars and I will continue to use it for future night sky updates.  If you want to download the Stellarium software go to www.stellarium.org

To find Lalande 21185 in Stellarium you will need to search for LAL 21185 or HIP 54035.

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

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

 

2013 Year of the Comet Part II

Earlier in the year we talked about 2013 as being year of the comet.  In the spring we had Comet PANSTARRS and for the end of the year we mentioned Comet ISON that was first predicated to become visible to the naked eye and had the chance to become as bright as the full moon.  Well, so far the year of the comet has not panned out as people were hoping for.  Comet PANSTARRS was supposed to become visible to the naked eye but for most it remained just beyond naked eye visibility.  It was still quite beautiful through binoculars and telescopes but it did not break the naked eye threshold for most observers. 

Perihelion for Comet ISON has now come and gone.  Like many comets ISON failed to survive its close approach to the Sun.  As a consolation for the demise of Comet ISON there are two other comets you can see in the morning skies.  These comets are named Lovejoy (C/2013 R1) and Linear X1.  Comet Lovejoy is easy to see in binoculars and Linear X1 will require a telescope.  Find out more information about these two comets and the demise of Comet ISON below.

General Comet Information

http://cometchasing.skyhound.com/

http://cometography.com/

Star Charts Showing Comet Locations in the Sky

http://www.aerith.net/comet/weekly/current.html

http://freestarcharts.com/images/Articles/Month/Dec2013/Comet_Lovejoy/C2013_R1_Lovejoy_Dec_2_Finder_Chart.pdf

http://freestarcharts.com/images/Articles/Month/Dec2013/Comet_LINEAR/C2012_X1_LINEAR_Dec_2013_Finder_Chart.pdf

Demise of Comet ISON

http://science.nasa.gov/media/medialibrary/2013/12/02/ison_anim.gif

http://www.isoncampaign.org/Present

Comet Update 12/23/2013:

Comet Lovejoy (C/2013 R1): This comet remains a great comet through a pair of binoculars and can now be found in the constellation Hercules. It is shining at magnitude 4.9 making it an easy target in a pair of binoculars and should be visible to the unaided eye away from city lights.  Use the finder chart above to locate this comet.

Comet Linear X1: This comet is hanging at 9th magnitude so it should still be visible in small telescopes.  Use the link above to find daily locations for this comet.

NASA Mission of the Month

Each month we will be celebrating a NASA mission of the month.  This month’s mission is the Solar and Heliospheric Observatory (SOHO).  This is a telescope that dedicates it’s time to observing the Sun.  Telescopes like SOHO and its predecessor the Solar Dynamics Observatory (SDO) have revolutionized the fields of solar physics and stellar astronomy.  Our understanding of how the Sun functions has changed dramatically since the launch of SOHO.  In addition to the Sun, SOHO has helped observe comets, asteroids and anything else that moves within its field of view.  It is a fascinating telescope that provides us with a front row seat to the most important object in our solar system.  To learn more visit

http://sohowww.nascom.nasa.gov/home.html

 

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, January 3, 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 8:00 p.m.  Regardless of the weather on January 3, 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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