This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Saturday, April 19, 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 radiant for the Lyrid meteor shower can be found rising in the northeast around 23:00. Image created using Stellarium.
The morning sky continues to be a point of interest this month as planets have returned to predawn hours. Additionally, the peak of the Lyrid meteor shower occurs this week which is best viewed in predawn hours. The Moon continues to wane as the lunar phases shift from gibbous to crescent. Along the way the Moon will pass by three planets as it approaches new moon later this month.
The Moon reaches last quarter on April 20, 2025, and new moon on April 27, 2025. A few days before new moon, the Moon reaches perigee which means large tidal fluctuations will be larger than normal at the start of the next lunation. While this does not have a huge impact on us in St. Louis, those that live on the coasts or may be traveling there should be aware of this. If you would like to learn more about the impact of tidal conditions visit NOAA’s Tide & Currents page.
The Moon visits the planets Venus and Saturn on April 25, 2025, appearing 5° east of Venus and 5° north of Saturn by the time the trio is visible in St. Louis. On this same morning Mercury will appear about 6° east of the Moon. Mercury will be challenging to spot due to how low to the horizon it will appear. Around 05:45 CDT, Mercury will only be 5° above the horizon. If you have binoculars and a clear view of the eastern horizon, you might be able to spot Mercury at this time.
Mercury reaches greatest western elongation on April 21, 2025, when it will reach a solar elongation of 27°. While this is Mercury’s greatest separation from the Sun this year, it will be a difficult apparition to see from St. Louis due to the low angle of the ecliptic at sunrise.
This week, Venus continues to exhibit a crescent phase going from 18.9% disk illumination on April 19 to 26% disk illumination on April 27. Venus reaches its greatest illuminated extent on April 27, 2025. Greatest western elongation for Venus occurs on May 31, 2025, around 23:00 CDT. The day after this Venus will be seen in dichotomy as it transitions from a crescent phase into gibbous phases.
Lastly, the Lyrid meteor shower started on April 17, 2025, and will continue through April 26, 2025. Peak activity occurs on April 22, 2025, at 1300 UT which is 0800 CDT. The best night to view these meteors starts on April 21, 2025, once the radiant for the Lyrids clears tree lines. The Lyrid radiant is found about 7° south of the bright star Vega which rises in the northeast around 22:00. Start looking for Lyrids emanating from the northeastern direction a little after 23:00 on April 21, 2025. As the radiant climbs higher in the sky, you will see meteors emanating in all directions. The Lyrid radiant is found near the border of the constellations Lyra and Hercules which culminate around 04:00 on April 22, 2025.
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 10.5.
The Sun and Moon
The Moon as seen from the International Space Station, on July 31, 2011.
Credit: NASA
Sun
Sunrise is at 06:18 on Saturday, April 19 and sunset is at 19:42 providing about 13.5 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 21:18 this week. For those with a sundial, local noon occurs around 13:00 on April 19, 2025.
Moon
Moonrise for Saturday, April 19, was at 01:31 and moonset occurred at 10:27. The Moon starts the week off exhibiting a waning gibbous phase with 63% disk illumination. By the end of the week the Moon will be at new moon. First quarter moon occurs on May 4, 2025, at 08:52 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. 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 westat 20:30 on April 20, 2025. Credit: Stellarium, EG
Looking east at 05:45 on April 21, 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 rises this week around 05:24. 30 minutes before sunrise, Mercury will be below 10° above the horizon so it will be difficult to find for most. Maximum western elongation occurs on April 21, 2025, and superior conjunction occurs on May 25, 2025.
Venus
Venus has begun a morning apparition. This means that Venus will be visible in the east before sunrise for the next several months. Venus will be at its greatest illuminated extent on April 27, 2025. Look for Venus about 45 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 02:30 this week.
Jupiter
Jupiter will be visible high in the west not long after sunset. Jupiter sets by 23:34, remaining visible up to 22:00. 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° 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 19-27, 2025
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