This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Tuesday, July 26. 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, August 5, 2016 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 5:58 a.m. on Tuesday, July 26 and sunset is at 8:17 p.m. providing us with a little under 14.5 hours of daylight. Even after sunset, the light from the Sun will still dimly illuminate our sky for nearly two hours. This period of time is called twilight, which ends around 10:04 p.m. this week. For those with a sun dial, solar transit or local noon occurs around 1:08 p.m. this week.
Moonrise for Tuesday, July 26 occurs at 11:58 p.m. on the preceding day and moonset will occur at 1:11 p.m. On July 26 the Moon will be in last quarter phase.
International Space Station (ISS) Observing
Visible passes of ISS from St. Louis for the week of July 26 are during the morning and evening hours. The best of these occur on the evenings of July 26 and 27. Use the table below for more information regarding these passes and others occurring this week.
Catch ISS flying over St. Louis starting Tuesday, July 26.
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:
The Planets Visible Without a Telescope
Both Mercury and Venus are in the process of starting another evening apparition. Of the two Venus will be the only one that we will have a decent chance of seeing before August. Unfortunately this evening apparition of Mercury will not be very good as Mercury’s altitude 30 minutes after sunset only reaches 5°. Mercury will reach maximum eastern elongation on August 16, 2016.
Venus is starting another evening apparition so be on the lookout for the brightest planet low in the west just after sunset. Any kind of tree cover or buildings to the west will obscure your view so make sure to get to a place with as clear of a western view as possible. The glare of the twilight sky will also pose a problem so you might need binoculars to spot Venus. Your best chance to see Venus right now will be to get to a high spot between 8:30 and 9:00 p.m. and scan the western horizon around azimuth 290° which will be in the northwest. This unfortunately will only be about 15 minutes after sunset so use caution and make absolute sure that the Sun has set as looking directly at the Sun can do irreversible eye damage. Viewing times will slowly get better as the week progresses. Venus reaches maximum eastern elongation on January 12, 2017.
The Red planet is currently found in Libra rising before the Sun and can be easily seen by 9:00 p.m. in the southern sky. Mars sets by 1:07 a.m.
Jupiter now rises before the Sun sets. To see Jupiter you will have to look high in the west at about 8:40 p.m. Jupiter sets at 10:27 a.m. Each week Jupiter will set approximately 30 minutes earlier than it did the week before.
NASA’s Juno mission arrived at Jupiter on Monday, July 4. Juno’s primary mission started with orbital insertion on July 4, 2016 and will end when the spacecraft is deorbited allowing the spacecraft to descend into the crushing atmosphere of Jupiter in February 2018. Over 20 months Juno will complete 37 orbits during which the spacecraft will investigate Jupiter’s core and magnetic field, measure the amount of ammonia and water in Jupiter’s deep atmosphere and it will observe the planet’s aurora and charged particle environment. To learn more visit https://www.nasa.gov/mission_pages/juno/main/index.html
The ringed planet is has reached opposition and as such rises before the Sun sets. Look for Saturn alongside Mars in the southern sky about 30 minutes after sunset. Saturn will set by 2:12 a.m.
Deep Sky Object of the Week
A few years ago the night sky update included a section that highlighted one constellation a month and a few objects of interest inside of it. Unfortunately of the 88 constellations there are only about 60 we can see in St. Louis and of these there are only so many that have enough objects to reference that would interest both beginners and advanced observers. In 2015 we changed things a bit for this section and instead of highlighting one constellation for each month we highlighted one Messier object a week using the Astronomical League’s Binocular Messier program as our guide. We will continue this into 2016 but instead of using the Astronomical League’s binocular Messier program we will use their Binocular Deep Sky Program.
The Astronomical League is an amateur astronomy society that is composed of over 240 local amateur astronomy societies across the United States and includes members at large and other supporting members. Their goal is to promote the science of astronomy through education, incentive and communication.
One of the many ways the Astronomical League has assisted amateur astronomers around the world is by creating various observing programs that highlight different aspects of astronomy and how an amateur astronomer can observe the sky and learn more about astronomy in doing so. Some of these programs are introductory and are targeted at those beginning to learn about observational astronomy and some are extremely advanced, require specialized equipment and require a large amount of time to complete. These observing programs cover most any type of object or way to observe the sky so everyone should be able to find one that matches their interests and abilities. It is important to note that these programs are not part of any class or lecture series but are rather lists of objects that highlight types of objects or observing methods relevant to astronomy. Taking part in these programs is done under one’s own choice. To officially complete each program you do have to be a member of the Astronomical League but you do not have to join to use them as observing guides or education tools. I would urge anyone interested in astronomy to look at these programs as they will help organize observing sessions and will help refine observing skills you already have. You can find out more information about the Astronomical League’s observing programs here https://www.astroleague.org/observing.html
The observing program we will use to help guide us through the 2016 observing year is the Binocular Deep Sky Program. This is a program that will appeal to both beginning and advance observers. Too often it is thought that you need to have a telescope for astronomical observations. Telescopes make great observing tools and yes they can show you more than binoculars but they do have their limitations. Cost, size, weight and complexity will often be a surprise to people when they first learn about telescopes. These factors can keep people from using telescopes they own or from buying one at all. The best advice to follow is a good observing tool is one you will use.
The binocular deep sky program is an introduction to deep sky objects beyond the Messier catalog. It will introduced viewers to the New General Catalog (NGC) and some of the lesser known deep sky catalogs such as the Stock, Collinder and Melotte. Each week we will highlight a deep sky object that is part of the Astronomical League’s binocular deep sky program. This program is tougher than Messier binocular program as the objects are not always as obvious and they will require larger binoculars than the Messier program. 50mm binoculars are recommended but many of the targets can be seen through smaller aperture instruments. I would urge each observer to fulfill the requirements of the program even if you do not intend to join the League for completion. The requirements involve logging observing data that can help refine observing skills that will be useful later down the road. If you have an interest in astronomy and learning more about observational astronomy I would also recommend checking out one of the two excellent astronomy societies near St. Louis. Both are members of the Astronomical League and both do numerous public observing nights around town. These clubs are the
If you do not live in the St. Louis, Missouri area chances are you have similar astronomical societies where you live.
The deep sky object for the week of July 5 is the open star cluster NGC 6823. Found in the constellation Vulpecula you can find NGC 6823 rising in the east by 11:00 p.m. At a distance of about 8,800 light years NGC 6823 shines with an apparent magnitude of 7.1. At this magnitude NGC 6823 will be a tough pull for city observers. This star cluster is estimated to have 30 members that are only two million years old. NGC 6823 has a Trumpler classification of I, 3, p, n which means it is well detached from background stars with a strong central concentration, it has a wide variety of stellar magnitudes, it has a poor population with less than 50 members and it is associated with a nebula.
To find NGC 6823 you will need to find the constellation Vulpecula. This can be a hard constellation to see but finding it is simple as it is a minor part of the famed Summer Triangle. Start by locating the three triangle stars Deneb, Vega and Altair. These stars are members of the constellations Cygnus, Lyra and Aquila respectively which can be seen rising in the east by 10:00 p.m. Once you can identify Cygnus look on its east side for a rather dim patch of sky this will be Vulpecula. Once here you will need to find two more stars named Alberio (Beta Cygnii) in Cygnus and Gamma Sagittarii in Sagitta. The easiest way to find these stars is to start with Deneb which is the tail of Cygnus and pan down his body until you find Alberio. From here pan to the southeast until you find the arrow shape of Sagitta. Once the two stars are located pan back and forth with your binoculars and you will find NGC 6823 about halfway between Alberio and Gamma Sagittarii. This week’s target will be one that Stellarium will be of great assistance. You can also use the link below to find maps of all constellations and stars used as guides.
The deep sky object for the week of July 12 is the open star cluster NGC 6910. This open star cluster is located in the constellation Cygnus the Swan near the bright star Gamma Cygnii (Sadr). At a distance of about 5,400 light years this young group of stars shines with an apparent magnitude of 7.4. The stars in this cluster are estimated to be about 10 million years old. NGC 6910 has a Trumpler classification of I, 2, p indicating it is well detached from background stars with a strong central concentration, is has a moderate range of stellar magnitudes and it has a poor population having only 50 member stars.
When looking at this cluster you should notice two bright stars that appear yellow. The northern of the two is the star SAO 49556 and the southern is V2118 Cygnii. The later of these is visually interesting as it appears yellow but it is has a b-spectral class indicating it should appear blue. The reason for this visual oddity is the result of interstellar reddening. Much like our atmosphere causes sunsets to appear red, dust and gas in space absorb and scatter light from stars causing their appearance to change.
Finding NGC 6910 is pretty simple as it is located next the star Sadr in the constellation Cygnus. To find this area we will first have to locate the Summer Triangle. This famous asterism can be found by locating the three stars Deneb, Vega and Altair. These stars are members of the constellations Cygnus, Lyra and Aquila respectively which can be seen rising in the east by 10:00 p.m. Once you can identify the star Deneb in Cygnus, Sadr is the next bright star to the southwest about 6° from Deneb. Once you identify Sadr (Gamma Cygnii) grab your binoculars and look just north of Sadr and you will find a fuzzy patch of stars that is NGC 6910. Use the links below for assistance in finding our deep sky target this week.
The deep sky object for the week of July 19 is the globular star cluster NGC 6934. This star cluster is different than those we have typically covered this year in that instead of a young group of ten to a few hundred stars, NGC 6934 is an ancient globular star cluster. These clusters are spherical shaped groups of stars that roam the Milky Way’s outer halo. They are older than stars in the galactic disk and help constrain the age of the universe as it must be older than the stars in it. The Milky Way has about 160 of these ancient star clusters many of which are seen in the summer months. NGC 6934 is located in the constellation Delphinus and is believed to be about 10 billion years old. At a distance of about 50,000 light years NGC 6934 shines with an apparent magnitude of 8.9. At this magnitude NGC 6934 will be a tough object to see in city light pollution.
To find NGC 6934 you will need to locate the constellation Delphinus. To do this once again start with the Summer Triangle. This famous asterism can be found by locating the three stars Deneb, Vega and Altair. These stars are members of the constellations Cygnus, Lyra and Aquila respectively which can be seen rising in the east by 10:00 p.m. Once you can find the star Altair in Aquila grab your binoculars and scan east until you see a bright group of four stars that form a diamond shape. This group is the head of Delphinus. From here scan about 8° south and you will find NGC 6934. Use the maps below for assistance.
The deep sky object for the week of July 26 is the open star cluster NGC 6940. This group of roughly 60 stars can be found in the constellation Vulpecula the Fox. At a distance of 2,600 light years NGC 6940 shines with an apparent magnitude of 6.3 making it an easy target for binoculars. At an age of one billion years NGC 6940 is old for an open cluster and as such it has a number of red giant stars. Around the time these stars first started to shine the supercontinent Rodinia was still the major landmass on the Earth. NGC 6940 has a Trumpler classification of III, 2, m which means it is well detached from background stars with no central concentration, It has a moderate range in stellar magnitudes and it has a moderate population with between 50 and 100 members.
To find NGC 6940 you will have to locate the Constellation Vulpecula. This can be a hard constellation to see but finding it is simple as it is a minor part of the famed Summer Triangle. Start by locating the three triangle stars Deneb, Vega and Altair. These stars are members of the constellations Cygnus, Lyra and Aquila respectively which can be seen rising in the east by 10:00 p.m. Once you can identify Cygnus look on its east side for a rather dim patch of sky this will be Vulpecula. Our target this week can be found near the border that separates the constellations Vulpecula and Cygnus. To find our target you will want to locate the stars Gamma and Epsilon Cygnii. Once you can identify these stars grab your binoculars and scan about 6° south of Epsilon Cygnii and you will find NGC 6940. It will appear as a nebulous patch of light through most binoculars. Use the maps below for help in locating our target this week.
Our next Star Party will be held on Friday, August 5, 2016, 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 August 5, 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.