This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Saturday, August 2, 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
Each year around mid-July, Earth encounters a stream of debris deposited by a comet called 109P/Swift-Tuttle which last passed through the inner solar system in 1992. With an orbital period of 133 years, 109P/Swift-Tuttle will not be near Earth again until 2125. While it will be some time until the comet returns, most of the debris shed by the comet remains spread along the comet’s orbit. Because of this, each year around mid-July, Earth begins to pass through the debris from historic orbits of the comet producing the famous Perseid meteor shower.
Most good meteor showers occur in the last half of the year with the Perseids being the first in that time frame. While the Perseids are active, we have to wait until August 12-13 for the shower to peak and as such the number of meteors one will see remains low until that peak time frame.
When viewing meteors showers there are a few factors to consider. Light pollution is a factor that most are aware of. The more lights around you the less meteors will be seen. If you are viewing from a light polluted location, position yourself in a way that still provides a view of the sky while placing yourself in a location that allows buildings or tree lines to obscure lights in the immediate area. A second factors is also related to light pollution however it is a natural source. The current moon phase plays a major role in how dark the sky appears to us. For the Perseids this year, the Moon will be near its full moon phase and as such it will be a problem. During good years, from a dark location, the Perseids can produce upwards of 100 meteors per hour at peak activity. This year will be diminished do to the Moon phase. If viewing from a light polluted area, expect to see 5 to 10 per hour.
Another factor is location. Get to as dark a site as possible. From St. Louis, you want to drive about two hours away to find darker skies. If that is not possible, get as far from the city as you can. A good resource to find dark places is visit your local DarkSky Chapter. You can find the Missouri chapter at Missouri DarkSky. If you are not in Missouri, visit DarkSky International to find your states chapter.
Lastly, all meteors exhibit a radiant. This is the point in the sky which meteors appear to emanate from. If you ever see a meteor streaking across the sky, its path will trace back to the radiant if the meteor is from a specific meteor shower. You can visit the American Meteor Society to figure out what showers are active on a given night. On this website you will find basic sky maps that indicate the radiant location of any active meteor shower. A radiant is typically named after the constellation contains it or in some cases the bright star it appears next to. The radiant for the Perseids is located in the constellation Perseus which is rising around 22:30. As the radiant climbs higher in the sky, you will see meteors moving in all directions. Make sure to not just look at the position of the radiant but rather be aware of its location.
The next major meteor shower is the Orionids in October. This meteor shower runs from October 2 to November 12 with a peak date of October 23, 2025. The source of these meteors is comet 1P/Halley. The Orionids are expected to produce roughly 20 meteors per hour on this date. The best time to view the Orionids comes after midnight when Orion is seen higher in the sky. On October 23, 2025, the Moon will exhibit a waxing crescent phase with roughly 6% disk illumination. This is great news for the Orionids this year as the Moon will set before the ideal viewing times.
T CrB Nova Update 8/2/2025
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 is overhead once it is dark. By 02:00, the constellation Corona Borealis will be found low 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 9.9.
The Sun and Moon
The Moon as seen from the International Space Station, on July 31, 2011.
Credit: NASA
Sun
Sunrise is at 06:04 on Saturday, August 2 and sunset is at 20:10 providing about 14 hours of daylight. Even after sunset, light from the Sun will dimly illuminate our sky for about 1 hour and 40 minutes. This period is called twilight, which ends around 21:54 this week. For those with a sundial, local noon occurs around 13:07 on August 2, 2025.
Moon
Moonrise for Saturday, August 2, was at 15:02 and moonset occurs at 00:31 the following day. On July 26, 2025, the Moon will exhibit a waning gibbous phase with 63% disk illumination. By August 4, 2025, the Moon will exhibit a waxing gibbous phase with 92% disk illumination. Full moon occurs on August 9, 2025, at 02:55 CDT.
International Space Station (ISS) Observing
There are no passes of ISS visible from St. Louis this week. ISS will return to St. Louis skies on August 15 when it is visible in morning hours.
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
Looking southwest at 21:00 on August 2, 2025. Credit: Stellarium, EG
Looking southeast at 05:15 on August 3, 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 in the southeast after midnight. 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 03:10. Look for Venus in the east around 04:00 as it clears tree lines.
Mars
Look for Mars in the western sky after sunset. The current apparition of Mars will continue throughout the rest of 2025. As the year continues, Mars will slowly appear closer to the western horizon each night. Mars sets around 22:09.
Jupiter
This week, Jupiter rises around 04:48. Look for Jupiter in the east around 05:15. On August 12, Jupiter will rise around 03:19 making it much easier to find before the Sun rises. On August 12, 2025, Jupiter and Venus will exhibit a conjunction during which they will appear only 51 arcminutes apart.
Saturn
Saturn is now visible in the southeast around midnight. It will be easy to spot as it is by far the brightest object in that part of the sky. Saturn rises this week around 22:27.
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 2-11, 2025
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