Night Sky Update - Week of March 14

This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Tuesday, March 14.  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, April 7, 2017 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 7:13 a.m. on Tuesday, March 14 and sunset is at 7:07 p.m. providing us with roughly 12 hours of daylight.  Even after sunset, the light from the sun will still dimly illuminate our sky for a little more than 1.5 hours.  This period of time is called twilight, which ends around 8:36 p.m. this week.  For those with a sun dial, solar transit or local noon occurs around 1:10 p.m. this week.

Day

Sunrise

Sunset

 14 Mar

7:13 a.m.

7:07 p.m.

 15 Mar

7:12 a.m.

7:08 p.m.

 16 Mar

7:10 a.m.

7:09 p.m.

 17 Mar

7:09 a.m.

7:10 p.m.

 18 Mar

7:07 a.m.

7:11 p.m.

 19 Mar

7:06 a.m.

7:12 p.m.

 20 Mar

7:04 a.m.

7:13 p.m.

 21 Mar

7:02 a.m.

7:14 p.m.

 22 Mar

7:01 a.m.

7:15 p.m.

The first day of spring is right around the corner.  This day is called the Vernal Equinox which occurs on March 20 this year.  After March 20 our days will continue to get longer and nights will get shorter until the first day of summer in June.  The reason this happens is due to Earth’s axial tilt.  We are tilted about 23.5° with regards to our orbit around the sun.  Due to our tilt we will be more inclined towards the sun causing it to appear higher in the sky. 

Using shadow lengths you can set up an experiment at home to observe the sun’s changing declination.  All you have to do is measure the length of a shadow on the ground cast by a gnomon at the same time each day.  Gnomons can be sticks, a tree or even a person, just make sure when you take your measurement the gnomon is in exactly the same place you took previous measurements from.  As we approach summer you should notice the shadows getting shorter. 

If you would like learn how ancient astronomers observed the equinox and solstices, Cahokia Mounds State Historic Site does sunrise observance of these days on the Sunday that is closest to the equinox or solstice.  The Vernal Equinox sunrise observance will be held on March 19, 2017.

For more information follow the link below. 

http://cahokiamounds.org/event/spring-equinox-sunrise-observance-7/

Moonrise for Tuesday, March 14 occurs at 9:20 p.m. and moonset will occur at 8:59 a.m. on the following day.  On Tuesday, March 14 the moon will be exhibiting a waning gibbous phase with about 95% of the lunar disk illuminated.  Last quarter moon occurs on March 20 at 10:58 a.m.

International Space Station (ISS) Observing

Visible passes of ISS from St. Louis for the week of March 14 occur in the morning hours.  The best of these occur on the mornings of March 19, 21 and 22.  Use the table below for information about these and other visible passes of ISS this week.

Catch ISS flying over St. Louis starting Tuesday, March 14                      

 

Mag

Starts

Max. altitude

Ends

Time

Alt.

Az.

Time

Alt.

Az.

Time

Alt.

Az.

17 Mar

-1.2

06:37:27

10

NNW

06:40:14

24

NNE

06:43:02

10

E

18 Mar

-0.7

05:45:26

10

NNW

05:47:41

17

NNE

05:49:56

10

ENE

19 Mar

-04

04:54:39

12

N

04:55:03

13

NNE

04:56:35

10

NE

19 Mar

-2.4

06:28:55

10

NW

06:32:09

49

NE

06:35:22

10

ESE

20 Mar

-1.4

05:37:12

13

NNW

05:39:41

28

NNE

05:42:36

10

E

21 Mar

-0.7

04:47:15

19

NNE

04:47:15

19

NNE

04:49:34

10

ENE

21 Mar

-3.3

06:20:35

10

WNW

06:23:51

64

SW

06:27:07

10

SE

22 Mar

-2.9

05:30:07

31

NNW

05:31:28

62

NE

05:34:45

10

ESE


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 can be seen low in the west about 20 minutes after sunset in the southwestern sky.  Venus sets by 8:33 p.m. 

Mars

The Red planet is currently found in Aries and can be seen 30 minutes after sunset in the southwestern sky.  Mars sets by 10:16 p.m.

Jupiter

The largest planet in our solar system has started another apparition and can be found rising in the east at 9:11 p.m.  It is currently found in the constellation Virgo and is best seen between the hours of 10:30 p.m. and 6:00 a.m. 

Saturn

The king of the rings is visible once again shortly before the Sun rises.  Saturn rises at 2:36 a.m. so your best chance to see it will start around 3:30 a.m. low in the southeastern sky. 

Constellation of the Month 2017

Over the last couple of years the night sky update has included information for locating a new deep sky object each week.  In 2017 we will change this by highlighting one constellation a month.  The first week of the month will always contain information regarding the constellation, its name, history and other such related topics.  Each week after will highlight a new object to look for.  A variety of objects will be highlighted but each month we will try to have an object that is visible through naked eye, binocular and telescope observations.

The constellation for the month of March is Ursa Major also known as the Big Bear.  Ursa Major is one of the best known constellations in the northern sky.  In ancient Greek folklore she represented the story of Calisto.  The Vikings called the pattern Karlavagen or Thor’s Chariot.  No matter the culture Ursa Major was linked to navigation.  Ursa Major is one of our circumpolar constellations.  It is close enough to the current North Star that all night and all year long Ursa Major is found circling in the northern skies.  In fact a pattern that is better known to us as the Big Dipper can be found inside the Great Bear’s boundary.  The handle of the dipper is the bear’s tail and the bowl is part of its back.  To find the North Star using the Big Dipper locate the two stars at the end of the dipper’s bowl called Merak and Dubhe.  Draw a line from Merak to Dubhe and keep moving above the bowl until you find another bright star.  This will be Polaris the North Star.  Due to its position in the northern skies many have looked to the great bear to travel the world. 

To find Ursa Major go outside after 7:00 p.m. and look to the northeast.  At this time you will find the Big Dipper with its handle pointing to the horizon and its bowl pointing towards the zenith.  The handle of the dipper is the bear’s tail the bowl is part of its back.  Use the map below to explore the constellation of Ursa Major and its brightest stars. 

https://www.iau.org/static/public/constellations/gif/UMA.gif

The object in Ursa Major for the week of March 7 is the red dwarf star Lalande 21185.  This is the 5th nearest star to the Sun.  Red dwarf stars are of particular interest for many reasons.  One reason is 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 type of 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 8:00 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 our 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 one of the toughest objects 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           

 

The object for the week of March 14 is the star system of Mizar and Alcor.  These two stars are of interest for a number of reasons.  One they are bright enough that they were known to ancient astronomers.  Often called the Horse and Rider this pair of stars has been used as an eye test.  The two stars are separated by about 14.4 arc seconds making them an easy double star to split.  Some people can spilt double stars down to about one arc second but that is stretching it for most observers. 

 

In addition to its ancient significance it is also a multiple star system.  As mentioned above it is a naked eye double star.  There are a number of naked eye doubles but most of them are not true double stars.  Mizar and Alcor are a physical double meaning they are part of the same gravitational system.  Mizar was the first telescopic double with the two components being named Mizar A and Mizar B.  Later through spectroscopic methods Mizar A, B and the star Alcor were discovered to be double stars as well meaning the together Mizar and Alcor form a six star system. 

 

To find Mizar and Alcor first locate the Big Dipper which can be found rising in the northeast by nightfall.  Next follow the stars of the dipper’s handle up to its bend, this is where you will find Mizar and Alcor.  On many maps together they will be labeled Zeta Ursa Majoris.  Use the map below for assistance.   

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

 

                                                 

    

Our next Star Party will be held on Friday, April 7, 2017, from dusk until 10 p.m.

 

As part of the Saint Louis Science Center’s First Fridays, 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 once it is dark.  Regardless of the weather on April 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 helps host the monthly Star Parties at the Saint Louis 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. 

 

 

 

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