This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Saturday, April 12, 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, May 2, 2025, held in association with the St. Louis Astronomical Society.
Observing Highlight of the Week
The image above shows the changing position of the planets, Venus, Mercury and Saturn this week. Image created using Stellarium.
For the first few months of 2025, we were treated to several planets that were visible in the early evening. As we shifted into March, several of these planets were lost to the Sun’s glare. Finally, these “lost” planets have returned to being observable. Unfortunately for many, these planets are now visible before sunrise.
The planets in question are Mercury, Venus and Saturn. Only Venus will be easy to find, however, Saturn is improving, and Mercury makes a brief visit to the eastern sky for the next week and a half.
Venus is easy to find in the east around 06:00 CDT. On March 22, 2025, Venus passed between Earth and the Sun as it reached inferior conjunction. Ever since then it has been climbing higher in the east just before sunrise. This week Venus rises around 05:00. It will be found 10° above the horizon around 05:50. I usually use the 10° mark as a threshold for visibility above tree lines. Those with clear views to the east, you should be able to find Venus as early 05:30. It all depends on your horizon.
Venus is approaching greatest illuminated extent on April 27, 2025. This is when Venus appears brightest to us. Venus is always brightest just before or just after inferior conjunction. This morning apparition will last through the rest of the year. Greatest western elongation occurs on May 31, 2025, and Superior conjunction occurs on Jan 6, 2026.
Mercury and Saturn will be much more difficult to find. At the start of the week, both planets are only 5° above the horizon 30 minutes before sunrise. By the end of the week, Mercury will still be found near the 5° mark, but Saturn will now appear about 9° above the horizon. No matter the date, Both Mercury and Saturn will be difficult to see due to the bright twilight sky.
T CrB Nova Update 4/13/2025
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 is rising earlier each night. By midnight, the constellation Corona Borealis will be found high in the eastern 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 06:28 on Saturday, April 12 and sunset is at 19:35 providing about 13 hours of daylight. Even after sunset, light from the Sun will dimly illuminate our sky for about 1 hour and 50 minutes. This period is called twilight, which ends around 21:09 this week. For those with a sundial, local noon occurs around 13:02 on April 12, 2025.
Moon
Moonrise for Saturday, April 12, was at 19:35 and moonset occurred at 06:32 the following morning. The Moon starts the week off at full moon. By the end of the week the Moon will be at Last quarter. New moon occurs on April 27, 2025, at 14:31 CDT.
International Space Station (ISS) Observing
Visible passes of ISS from St. Louis for the week of April 12 occur during morning hours. The table below lists the best of these passes that will be seen from St. Louis after April 18. 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
Looking east at 06:00 on April 13, 2025. Credit: Stellarium, EG
Looking southwest at 20:30 on April 13, 2025. Credit: Stellarium, EG
Possibly five naked eye planets will be visible this week. Mars and Jupiter are still visible after sunset once it is dark. Mercury, Venus and Saturn have returned to morning views becoming visible just before sunrise in the east.
Mercury
Mercury has begun its first full morning apparition of 2025. To have any chance of seeing this elusive planet, you will need to find a clear view of the eastern horizon. This week, Mercury will only appear about 5° above the horizon 30 minutes before sunrise making it difficult for most to spot.
Venus
Venus has begun a morning apparition. This means that Venus will be visible in the east before sunrise for the rest of the year. Venus will be at its greatest illuminated extent on April 27, 2025. Look for Venus about 30 minutes before sunrise in the east.
Mars
Look for Mars overhead high in the western sky after sunset. It is currently found near the bright stars Castor and Pollux. The current apparition of Mars will continue throughout the rest of 2025. Watch for the Red Planet as it shifts westward through the year. Mars sets around 02:57 this week.
Jupiter
Jupiter will be visible high in the west not long after sunset. Jupiter sets by 23:59, remaining visible up to 23:00. Jupiter reaches superior conjunction on June 24, 2025.
Saturn
Saturn has returned to morning visibility rising just before the Sun. Look for the planet in the east about 30 minutes before sunrise. It will be difficult to see in the bright twilight skies, however, it is just east of Venus. If you have binoculars, you can scan the sky about 5-6° east of Venus for a chance to spot Saturn.
Our next Star Party will be held on Friday, May 2, 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 May 2, join us indoors in our planetarium theater for our “Monthly Sky Lecture”.
This free, indoor star program will introduce you to the current night sky. Doors open 15 minutes before show time. Once a show is underway, there are 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. In addition to our nighttime viewings, they also help facilitate our daytime event called Solar Sundays. These daytime viewing sessions occur on the 3rd Sunday of each month. 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: April 12-20, 2025
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