This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Saturday, February 1, 2025.
Information updated weekly or as needed.
Times given as local St. Louis time this week will be in Central Standard Time (CST). 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 -6 hours when CST. Times posted in the Night Sky Update are in the 24-hour format.
Join us for our next star party, Friday, February 7, 2025, held in association with the St. Louis Astronomical Society. For details, see the information at the bottom of this page or use the button below.
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
These two daytime images of Venus show how the apparent size of Venus increases as it progresses through its phase cycle. Images credit: Eric Gustafson
If you have been watching the skies over the last few months, chances are you have seen the planet Venus. The planet is found not long after sunset in the southwest. The only object brighter than Venus at night is the Moon. You will see the Moon near Venus one more time before the end of Venus’s current apparition. This month Venus reaches its greatest illuminated extent on February 14. As Venus approaches this event, it can be possible to spot it naked eye during daylight hours.
Venus is expected to reach a peak magnitude around -4.9. Magnitude estimates at the start of February show Venus is currently around -4.7 magnitude.
To spot Venus in daytime hours, you need to know its position relative to the Sun. Using planetarium software such as Stellarium, you can determine Venus’s solar elongation and its altitude and azimuth at a given time. Once you have a general idea of where to look, I recommend moving so you have a tree or a roof line near Venus’s position. This is helpful as it can add a bit of contrast to the sky. To the unaided eye, Venus appears as a bright white dot. Trying to spot that against the bright day sky can be difficult. Any added contrast can make it easier to finally spot the planet.
If you have issues seeing Venus in the daytime, just wait until the Sun sets. Venus remains high in the southwestern sky for a few hours after sunset this month. While viewing at night, the phase of Venus can be seen using only binoculars. From the start of February, Venus will exhibit a crescent phase going from 37.3% illuminated to 14.6% illuminated on February 28. On the night of greatest illuminated extent, Venus will exhibit a phase of 27.2%.
Greatest illuminated extent occurs when Venus’s day side covers the most amount of sky. It might seem strange then that this occurs when Venus’s disk illumination is only 27.2%. Venus is brightest during crescent phases because it is closer to us and as a result it looks bigger. When the planet is exhibiting gibbous phases, its angular size can be as small as 10-arcseconds. During crescent phases, it will be around 40-arcseconds.
Anytime Venus is visible, it is worth viewing the planet. While visible to the unaided eye, it is a great target for those learning how to use a telescope. Unfortunately, we never can see the surface of Venus due to the dense cloud cover in its atmosphere. Instead, Telescopes reveal sharp views of the phase of Venus.
T CrB Nova Update 2/3/2025
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 1:30, the constellation Corona Borealis will be over 10° above the eastern horizon. This should make it visible for most if you have a decent view of the east. 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.
The Sun and Moon
The Moon as seen from the International Space Station, on July 31, 2011.
Credit: NASA
Sun
Sunrise is at 7:06 on Saturday, February 1 and sunset is at 17:23 providing around 10.5 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 18:54 this week. For those with a sundial, local noon occurs around 12:14 on February 1, 2025.
Moon
Moonrise for Saturday, February 1, was at 4:14 and moonset occurs at 21:17. The Moon starts the week off with a waxing crescent phase exhibiting 13% disk illumination. By the end of the week the Moon will exhibit a waxing gibbous phase with 91% disk illumination. First quarter moon occurs on February 5, 2025, at 2:02.
International Space Station (ISS) Observing
There is one visible pass of ISS visible from St. Louis for the week of February 1. It occurs during evening hours. After this pass ISS will return to St. Louis skies on February 12 as it switches to visibility during morning hours. The table below lists the best of these passes that will be seen from St. Louis. 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 south at 18:20 on February 3, 2025. Credit: Stellarium, EG
This week, four naked eye planets are visible. All four are visible in the evening sky not long after sunset. As we start to lose Saturn at the end of the month, Mercury will join the evening sky for a brief apparition.
Venus
Venus will be visible in the southwest after sunset. You can start looking for Venus about 15 minutes after the Sun sets. Venus will set by 21:04. Venus is now headed towards inferior conjunction which occurs on March 22, 2025. Over the next couple of months, Venus will continue to appear closer to the Sun until we lose Venus to the Sun’s glare.
Mars
Mars is now past opposition. Look for it rising in the east after sunset. The current apparition of Mars will continue throughout the rest of 2025. Watch for the Red Planet as it shifts westward through the year.
Jupiter
Now past opposition, Jupiter rises before the Sun sets. Look for Jupiter high in the east as the sky begins to darken. Jupiter sets around 2:57.
Saturn
Saturn will be visible in the southwest shortly after sunset. Saturn now sets around 19:58. Each week Saturn will set about 25 minutes earlier than it did the week before.
Our next Star Party will be held on Friday, February 7, 2025, from 5:30 pm until 8:30 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 February 7, join us indoors in our planetarium theater for our “Monthly Sky Lecture”. Showtime is at 7 p.m. This free, indoor star program will introduce you to the current night sky. Doors open 15 minutes before show time. Shows begins at 7 pm Sorry, 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: February 1-9, 2025
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