This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Saturday, July 15, 2023.
Information updated weekly or as needed.
Times given as local St. Louis time which is Central Daylight Time (CDT). For definitions of terminology used in the night sky update, click the highlighted text. If relying on times posted in Universal Time (UT), St. louis is -5 hours when CDT.
Public Telescope Viewings
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 4 , join us indoors in our planetarium theater for “The Sky Tonight”. Showtime is at 7 p.m. There is no First Friday event in July.
Observing Highlight of the Week
IAU map of the constellation Delphinus. Map credit: IAU
This week our highlight will the small constellation called Delphinus the Dolphin. Owing to its small size, objects to look for may seem limited, but there are a few wonderful targets for any level of observing experience. Delphinus was originally included in Ptolemy’s list of 48 constellations.
One of the myths associated with Delphinus tells the story of the poet Arion. As the poet was traveling back from a tour in southern Italy, the ship’s crew decided to rob Arion of his earnings. The poet convinced the crew to let him play one more song which attracted a group of dolphins. Arion jumped overboard allowing one of the dolphins to carry him to safety. As a reward, Apollo the Greek god poetry and music placed the dolphin in the sky to honor it.
Delphinus is easy to find as it is near the bright star Altair. Altair is one of the bright stars in the asterism known as the Summer Triangle. Look high in the east at 10 pm and the triangle should be obvious. The two other bright stars of the triangle are Deneb and Vega. Altair is found in the constellation Aquila which looks like a large diamond shape of stars. Looking roughly 10° east of Altair, you should see a small diamond shape. This is the constellation Delphinus.
The four bright stars in the small diamond shape is the head of the dolphin. They are the stars Beta, Alpha, Delta and Gamma Delphini. The brightest is Beta Delphini. Gamma Delphini is a nice double star that can be split with a backyard telescope. The two stars Gamma-1 and Gamma-2 appear separated by 9.2 arc seconds. Currently the pair of stars revolve in a period of 3200 years and are on average 330 AU apart.
Those with binoculars 10×50 and up have a chance to spot the globular star cluster named NGC 6934. While this cluster is a challenge in binoculars, it has a visual magnitude of 8.83 which puts it within grasp of moderate to large sized binoculars. The best view will be achieved with a telescope, but it is not necessary. At 8.8 magnitude, it will be tough to see in urban light conditions so travel somewhere darker if you are an urban astronomer.
NGC 6934 is roughly 50,000 light years away from us, making it one of the most distant objects we can see in the Milky Way. Like other globular clusters, it likely contains a few hundred thousand stars. It was discovered by William Herschel in 1785.
Delphinus is a small and often overlooked constellation, but it is worth a little bit of time these summer months.
The Sun and Moon
The Moon as seen from the International Space Station, on July 31, 2011.
Credit: NASA
Sunrise is at 5:48 a.m. on Friday, July 15 and sunset is at 8:25 p.m. providing us with a bit over 14.5 hours of daylight. Even after sunset, light from the Sun will dimly illuminate our sky for a little less than 2 hours. This period is called twilight, which ends around 10:18 p.m. this week. For those with a sundial, local noon occurs around 1:06 p.m. this week.
| Day | Sunrise | Sunset | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 15-Jul | 5:48 a.m. | 8:25 p.m. | ||||||||||
| 16-Jul | 5:49 a.m. | 8:24 p.m. | ||||||||||
| 17-Jul | 5:50 a.m. | 8:24 p.m. | ||||||||||
| 18-Jul | 5:51 a.m. | 8:23 p.m. | ||||||||||
| 19-Jul | 5:51 a.m. | 8:22 p.m. | ||||||||||
| 20-Jul | 5:52 a.m. | 8:22 p.m. | ||||||||||
| 21-Jul | 5:53 a.m. | 8:21 p.m. | ||||||||||
| 22-Jul | 5:54 a.m. | 8:20 p.m. | ||||||||||
| 23-Jul | 5:55 a.m. | 8:19 p.m. |
Moon
Moonrise for Saturday, July 15 is at 3:32 a.m. and moonset occurs at 7:23 p.m. On Saturday, July 15, the Moon will exhibit a waning crescent phase with 3% disk illumination. New moon occurs on July 17, 2023, at 1:32 p.m.
International Space Station (ISS) Observing
There are several visible passes of ISS from St. Louis for the week of July 15. They occur during evening hours and around the midnight hour in some cases. The best passes for this week are listed below. Use the table below for information about these passes.
Catch ISS from St. Louis starting Saturday, July 15
| Date | Starts | Max. altitude | Ends | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Time | Alt. | Az. | Time | Alt. | Az. | Time | Alt. | Az. | ||
| 22 Jul | -0.8 | 0:01:51 | 10 | NW | 0:02:45 | 16 | NNW | 0:02:45 | 16 | NNW |
| 22 Jul | -1.5 | 23:13:44 | 10 | NNW | 23:15:57 | 23 | N | 23:15:57 | 23 | N |
| 23 Jul | -1.4 | 22:25:40 | 10 | NNW | 22:28:03 | 18 | NNE | 22:29:09 | 15 | NE |
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 Visible Planets
Looking west at 9:00 p.m. on July 16, 2023. Credit: Stellarium, EG
Looking Southeast at 3:30 a.m. on July 17, 2023. Credit: Stellarium, EG
This week, four naked eye planets will be visible. Venus and Mars are found in the west after sunset. Saturn and Jupiter are visible in the southeast and east before sunrise.
Venus
The window to observe Venus is closing. Venus now sets around 9:52 p.m. Venus reaches inferior conjunction on August 13, 2023. Evening views of the planet will end as we reach August 1, 2023. Enjoy Venus while you can before it becomes a morning target later this year.
Mars
Mars now rises before sunset, becoming visible once it is dark. Look for it in the west about 30 minutes after sunset. Mars sets at 10:23 p.m.
Jupiter
Jupiter is starting another apparition. Jupiter rises at 1:17 a.m. About one hour after Jupiter rises, it should be easy to spot. Jupiter will rise about 20 minutes earlier each week.
Saturn
Saturn rises at 10:32 p.m. Start looking for Saturn about 30 minutes after it rises. If you have lots of trees or buildings, you may have to wait an hour or so after it rises before it will be visible.
James S. McDonnell Planetarium
Night Sky Update: July 15-23, 2023