This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Saturday, August 23, 2025.
Information updated weekly or as needed.
Times given as local St. Louis time this week will be in Daylight Saving Time. 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. Times posted in the Night Sky Update are in the 24-hour format.
Join us for our next star party, Friday, September 5, 2025, held in association with the St. Louis Astronomical Society.
For details, see the information at the bottom of this page or visit: https://www.slsc.org/explore/mcdonnell-planetarium/public-telescope-viewings
Observing Highlight of the Week
If you have been up before sunrise lately, chances are you have noticed two bright objects in the east around 5 am. If you have seen these, you have likely spotted the planets Venus and Jupiter. You can confirm you found planets with the twinkle test. Stars twinkle planets usually do not.
Earlier this month, Venus and Jupiter exhibited a conjunction appearing about 1° apart. Since then, the pair appears to be separating because Venus is headed towards superior conjunction and Jupiter is headed towards opposition. Over the next month or so look east before sunrise and track how the planets appear to move. These kinds of observations were part of how we discovered the solar system.
Superior conjunction occurs when a solar system body appears on the opposite side of the Sun from Earth. Inferior planets (Mercury and Venus) also exhibit inferior conjunction when they appear between Earth and the Sun. Superior conjunction for Venus occurs next year on January 6, 2026. As Venus shifts towards this point, it will appear closer to the Sun in the sky each day. After Venus reaches superior conjunction it will start and evening apparition becoming visible in the west after sunset.
Opposition occurs when superior planets (Mars through Neptune) appear nearest to the anti-solar point in the sky. This is when they appear opposite the Sun and their brightest for the current apparition. Jupiter reaches opposition on January 10, 2026.
As we near the end of 2025, the two planets that appeared about 1° apart will eventually appear in opposite parts of the sky. For those without telescopes, this is a great observing project.
If you have been following the Titan shadow transits this year, there are only three more before we have to wait 15 years for the next chance. These occur on September 4, 2025, September 20, 2025, and October 6, 2025. If you are interested in learning more check out the article on Sky and Telescope regarding this topic.
T CrB Nova Update 8/25/2025
If you are still interested in seeing the recurrent nova T Coronae Borealis, there is still hope. The nova has not yet occurred meaning we are in a waiting game. It could happen this year or it could happen next year. We will have to wait and see. If you are still interested in this event, the part of the sky the nova will appear in the west once it is dark. By 01:30, the constellation Corona Borealis will be setting in the western sky. Spaceweather.com is still posting magnitude estimates from the AAVSO. This is the resource I recommend following to keep up with any changes in the star’s brightness. Current magnitude of the system is 9.7.
The Sun and Moon
The Moon as seen from the International Space Station, on July 31, 2011.
Credit: NASA
Sun
Sunrise is at 06:22 on Saturday, August 23 and sunset is at 19:44 providing around 13 hours of daylight. Even after sunset, light from the Sun will dimly illuminate our sky for about 1 hour and 30 minutes. This period is called twilight, which ends around 21:19 this week. For those with a sundial, local noon occurs around 13:03 on August 23, 2025.
Moon
Moonrise for Saturday, August 23, is at 06:39 and moonset occurs at 20:06. On August 23, 2025, the Moon reached new moon around 01:07. By September 1, 2025, the Moon will exhibit a waxing gibbous phase with 63% disk illumination. First quarter moon occurs on August 31, 2025, at 01:25 CDT.
International Space Station (ISS) Observing
Visible passes of ISS from St. Louis for the week of August 23 occur during morning hours. The table below lists the best of these passes. If you do not live in the area, you can use https://heavens-above.com/ to set your viewing location and get times for where you are.
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°.
Detailed information regarding all unmanned exploration of our universe, missions past, present, and planned, can be found at Jet Propulsion Laboratories
The Visible Planets
Positions of Mars and Saturn August 25, 2025. Credit: Stellarium, EG
Looking east at 05:00 on August 26, 2025. Credit: Stellarium, EG
Four naked eye planets will be visible this week. Mars is visible in the west after sunset once it is dark. Saturn is visible around 22:00. Venus and Jupiter are visible before sunrise in the east.
Venus
Venus is found in the east before sunrise for the rest of the year. It currently rises around 03:41. Look for Venus in the east around 05:00. Venus reaches superior conjunction on January 6, 2026.
Mars
Look for Mars in the western sky after sunset. The current apparition of Mars will continue throughout the rest of 2025 however twilight will make find Mars increasingly difficult. As the year continues, Mars will slowly appear closer to the western horizon each night. Mars sets around 21:17 this week.
Jupiter
This week, Jupiter rises around 02:43. Look for Jupiter in the east around 04:00. Jupiter reaches opposition on January 10, 2026. As we continue towards this date, Jupiter will continue to rise earlier each week.
Saturn
Saturn is now visible in the southeast around 22:00. It will be easy to spot as it is the brightest object in that part of the sky. Saturn rises this week around 21:02.
Our next Star Party will be held on Friday, September 5, 2025, from 6:30 pm until 9:30 pm
On the first Friday of each month, the St. Louis Astronomical Society and the Saint Louis 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 1, join us indoors in our planetarium theater for our free monthly sky lecture.
The St. Louis Astronomical Society helps host the monthly Star Parties at the Saint Louis Science Center. In addition to our nighttime viewings, they also help facilitate our daytime event called Solar Sundays. These daytime viewing sessions occur every Sunday through Labor Day from 11:00-15:00 weather permitting. Visit SLAS’s website linked above to learn about other telescope events SLAS hosts around the St. Louis area.
James S. McDonnell Planetarium
Night Sky Update: August 23-September 1, 2025
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