This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Tuesday, February 14.  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 3, 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 6:53 a.m. on Tuesday, February 14 and sunset is at 5:38 p.m. providing us with roughly 10.5 hours of daylight.  Even after sunset, the light from the Sun will still dimly illuminate our sky for roughly 1.5 hours.  This period of time is called twilight, which ends around 7:01 p.m. this week.  For those with a sun dial, solar transit or local noon occurs around 12:15 p.m. this week.




 14 Feb

6:53 a.m.

5:38 p.m.

 15 Feb

6:51 a.m.

5:39 p.m.

 16 Feb

6:50 a.m.

5:40 p.m.

 17 Feb

6:49 a.m.

5:41 p.m.

 18 Feb

6:48 a.m.

5:43 p.m.

 19 Feb

6:46 a.m.

5:44 p.m.

 20 Feb

6:45 a.m.

5:45 p.m.

 21 Feb

6:44 a.m.

5:46 p.m.

 22 Feb

6:43 a.m.

5:47 p.m.

Moonrise for Tuesday, February 14 occurs at 9:35 p.m. and moonset will occur at 9:30 a.m. on the following day.  On Tuesday, February 14 the Moon will be exhibiting a waning gibbous phase with about 85% of the lunar disk illuminated.  Last quarter moon occurs on February 18 at 1:33 p.m.

International Space Station (ISS) Observing

Visible passes of ISS from St. Louis for the week of February 14 occur in the evening hours.  The best of these occurs on the evening of February 16.  Use the table below for information about this and other visible passes of ISS this week.

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



Max. altitude


Time Alt. Az. Time Alt. Az. Time Alt. Az.
14 Feb -2.7 18:13:04 10 NW 18:16:10 38 NNE 18:19:12 10 ESE
14 Feb -0.7 19:49:58 10 W 19:51:54 19 WSW 19:51:54 19 WSW
15 Feb -2.1 18:57:02 10 WNW 19:00:07 40 SW 19:02:27 15 SSE
16 Feb -3.3 18:04:26 10 NW 18:07:43 86 SW 18:10:57 10 SE
17 Feb -0.4 18:49:17 10 W 18:51:22 16 SW 18:53:28 10 S


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

Detailed information regarding all unmanned exploration of our universe, missions past, present, and planned, can be found at Jet Propulsion Laboratories:


The Planets Visible Without a Telescope


Venus can be seen low in the west about 20 minutes after sunset in the southwestern sky.  Venus sets by 9:03 p.m.


The Red planet is currently found in Pisces rising before the Sun and can be easily seen 30 minutes after sunset in the southwestern sky.  Mars sets by 9:24 p.m.


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


The king of the rings is visible once again shortly before the Sun rises.  Saturn rises at 3:19 a.m. so your best chance to see it will be around 4:30 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 February is Gemini the Twins.  Located in the winter sky, Gemini will be easily seen in the east once twilight ends.  The constellation Gemini is easy to locate due to its location next to Orion the Hunter.  To find Gemini all you have to do is first locate Orion and follow a path from the stars Rigel to Betelgeuse and you will find a rectangle shape of bright stars to Orion’s northeast.  This rectangle shape of stars is the constellation Gemini.

The name Gemini is related to the Greek myth of the twins Castor and Pollux.  The twins shared a mother however their fathers were different.  Immortal Pollux was the son of Zeus and Castor was mortal son of King Tyndareus.  The twins were very close partaking on many adventures together.  They were part of the Argonauts that traveled with Jason and sadly it is during one of these adventures that the mortal Castor was slain.  Stricken with grief over the loss of his brother Pollux pleaded to join his brother in Hades.  Zeus agreed and placed him alongside his brother Castor in the sky so they could spend part of their time in Hades and part of the time with the rest of the Olympians in the sky.  Use the maps below for assistance in locating Gemini.

The first target in Gemini we will cover this month is the asteroid 4 Vesta.  This is the second largest body in the main asteroid belt being roughly the size of Pakistan.  Vesta’s average distance from the Sun is 2.36 AU which is about 219,647,000 miles.  Vesta’s orbital period is about 3.63 Earth years.

One of the unique things about Vesta is its high mass and density for its size.  The high mass and density of Vesta can be explained by a concept called differentiated.  Differentiation is a process in which planetary interiors are separated into different constituents of a planetary body by physical or chemical behaviors.  In the case of objects like Vesta these behaviors were impact events, gravitational pressure and radioactive decay.  These all increased the temperature of Vesta’s interior which allowed materials to become molten or more plastic.  When these kind of scenarios occur less dense material rises and denser material migrates to the core.  One sign that Vesta was differentiated came in the form of HED meteorites.  These meteorites show signs of differentiation and are thought to be from Vesta due to spectral analysis.  In 2011 the Dawn spacecraft orbited the asteroid for a year providing information confirming that Vesta was indeed differentiated and that HED meteorites were likely fragments of Vesta.  What these findings show us is that Vesta is one of if not the last of the proto-planets.

Vesta reached opposition on January 18 so it is currently near its brightest it will be for the year.  With an apparent magnitude of 6.7 it will be an easy target for binocular observers.  To locate Vesta you will have to find the stars Kappa and Upsilon Geminorum.  These are the two brightest stars just south of the bright star Pollux.  The asteroid 4 Vesta can be found about 1/3 the distance between these stars if you star at Kappa Geminorum.  Use the maps below for help in finding Vesta.

The object for the week of February 14 is the open star cluster Messier 35 (M35).  M35 is a cluster of roughly 200 stars that formed from a large cloud of dust and gas about 110 million years ago.  As star ages go this is a young group of stars that started to shine when dinosaurs still roamed the Earth.  At a distance of 2,800 light years it has an apparent magnitude of 5.1 making it an easy target for binocular observers.  When looking for M35 you might find that locating the star cluster is not as easy as you thought it would be.  The reason is it covers a large part of sky.  To us on Earth M35 has an angular appearance of 12 arc minutes.  By comparison a full moon covers about 30 arc minutes.  One tool that can help understand what an open star cluster will look like is the Trumpler Classification system.  This system was created by astronomer Robert Julius Trumpler.  He created this system to classify open star clusters based on visual characteristics.  Using Trumpler’s system M35 is listed as an III, 2, m star cluster which means it is detached from background stars but has no central concentration, it has a moderate range of stellar magnitudes and it has a moderate population having between 50 and 100 stars.  You might notice this last part does not agree with the number of stars listed at the beginning of this section.  Unfortunately many of these classifications were done some time ago so they do not always agree with modern analysis.  To learn more about the Trumpler system look at page 5 of the Astronomical League’s open star cluster observing program.

To find M35 you will have track down the star Eta Geminorum.  This star can be found in the feet of the twin Castor.  Start by locating the constellation Orion.  Identify the two stars Saiph and Betelgeuse.  Once this is accomplished star hop from Saiph to Betelgeuse continuing north about the same distance you see between these two stars.  In other words you will look about 20° north of the star Betelgeuse.  Once you find Eta Geminorum, M35 is about 1° northwest of this bright star.  Use the maps linked below for further assistance.

Our next Star Party will be held on Friday, March 3, 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 March 3, 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.