This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Friday, March 29, 2023.
Information updated weekly or as needed.
Times given as local St. Louis time which is 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. Day Light Saving time starts on March 12, 2023, and run through November 5, 2023. Once in DST, St. Louis will be five hours behind UT.
Public Telescope Viewings
As part of the Saint Louis Science Center’s First Fridays, weather permitting, the St. Louis Astronomical Society and the 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 April 7, join us indoors in our planetarium theater for “The Sky Tonight”. Showtime is at 7 p.m.
Observing Highlight of the Week
View of Venus’ northern hemisphere. Recently, scientists found evidence that supports Venus is still volcanically active. You can learn more here. Image credit: NASA/JPL.
Venus is well into its current evening apparition. You will find Venus high in the west after sunset. Venus will remain an evening target up to the start of August this year. Venus reaches inferior conjunction on August 13, 2023, which is when it passes between the Earth and Sun. As we near this date, Venus will gradually be lost to the glare of the Sun. After June 4, 2023, Venus will appear nearer the Sun each day. August 8, 2023, is when I recommend most viewers stop looking for Venus due to how close the planet will appear to the Sun. Venus’ solar elongation will only be 10.8° by the 8th which is getting a little too close for comfort. Once we get to August make absolute sure the Sun has set before looking for Venus. Through the start of August several events involving Venus will be visible. These include several pairings with the Moon, and a close pairing with Mars.
Each month the Moon passes by all the planets as it shifts through the zodiac constellations. Since Venus is currently seen in the west after sunset, we will see the planet pair with a waxing crescent moon each month. The dates on which the Moon will be near Venus for the current apparition are April 22/23, May 22/23, June 21, and July 20, with the best being June 21. On this date, we will see the Moon and Venus about 3° apart.
At the beginning of June, Venus will reach a few key points in its orbit. From our perspective on Earth, Venus exhibits phases because it is closer to the Sun. Planets that are closer to the Sun from our viewpoint are called inferior planets. Inferior planets reach solar conjunction twice during an orbit. Inferior conjunction occurs when they pass between Earth and the Sun, while superior conjunction is when they pass behind the Sun. As Venus starts an evening apparition, it is moving out of superior conjunction. Venus will exhibit gibbous phases until it reaches dichotomy. Dichotomy is when a planetary disk appears half illuminated by the Sun. This occurs for Venus on June 3, 2023.
After this date, Venus will exhibit crescent phases until it reaches inferior conjunction. Dichotomy occurs when an inferior planet is near greatest elongation. Elongation is an angular measurement of how far something appears from another object as seen from Earth. When Venus reaches greatest eastern elongation on June 4, 2023, it will appear roughly 45° from the Sun.
July is the last full month of the current Venus apparition. On July 1, 2023, Venus and Mars will exhibit an appulse. An appulse is when two or more astronomical objects make a close approach to one another. Unfortunately, the moment of appulse occurs in daytime for St. Louis. However, 30 minutes after sunset, the pair of planets will still be a nice sight. On July 7, 2023, Venus will appear at its brightest. Even though it will exhibit a crescent phase, Venus will be closer to Earth making it appear brighter.
On July 20, Venus and Mars will be joined by the Moon but the trio of objects will be low enough that trees may become a problem. From this point on, any view of Venus will need a clear view of the west. While visible, binoculars will be enough to see the crescent phase of Venus but be sure that the Sun has set before looking.
The last event we may see before the apparition ends is a grouping of Mars, Venus and Mercury on July 26, 2023. This will be very challenging to see, as Venus and Mercury will be under the 10° threshold and Mars will appear dim in the bright twilight glow. For most of us, this grouping of planets will likely go unseen. For those that want to try to see it, the best chance will come from a location with elevation. Something like a parking garage that is taller than trees and buildings around it. Sunset occurs at 8:20 p.m. 10 minutes later Venus should be visible, but it will be just under 4° from the horizon. To have a chance to see Mercury and Mars, you will need to use binoculars but be sure the Sun has set. The Sun will damage your eyes if you accidentally see it through binoculars.
Venus will be a spectacular early evening sight up to August this year. As we near the end of Venus’ evening apparition, the majority of planets will have shifted to morning views before sunrise. Venus will follow suit by September later this year. As we turn our sights to mornings skies, Saturn and Jupiter will become the best planets to see.
The Sun and Moon
The Moon as seen from the International Space Station, on July 31, 2011.
Credit: NASA
Sunrise is at 6:50 a.m. on Wednesday, March 29 and sunset is at 7:21 p.m. providing us with roughly12.5 hours of daylight. Even after sunset, light from the Sun will dimly illuminate our sky for roughly 1 hour and 30 minutes. This period is called twilight, which ends around 7:31 p.m. this week. For those with a sundial, local noon occurs around 1:06 p.m. this week.
| Day | Sunrise | Sunset | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 29-Mar | 6:50 a.m. | 7:21 p.m. | ||||||||||
| 30-Mar | 6:49 a.m. | 7:22 p.m. | ||||||||||
| 31-Mar | 6:47 a.m. | 7:23 p.m. | ||||||||||
| 1-Apr | 6:46 a.m. | 7:24 p.m. | ||||||||||
| 2-Apr | 6:44 a.m. | 7:25 p.m. | ||||||||||
| 3-Apr | 6:43 a.m. | 7:26 p.m. | ||||||||||
| 4-Apr | 6:41 a.m. | 7:27 p.m. | ||||||||||
| 5-Apr | 6:40 a.m. | 7:28 p.m. | ||||||||||
| 6-Apr | 6:38 a.m. | 7:29 p.m. | ||||||||||
| 7-Apr | 6:37 a.m. | 7:30 p.m. | ||||||||||
| 8-Apr | 6:35 a.m. | 7:31 p.m. |
Moon
Moonrise for Wednesday, March 29 is at 12:05 p.m. and moonset occurs at 3:49 a.m. on the following day. Wednesday, March 29, the Moon will exhibit a waxing gibbous phase with 57% of the lunar disk illuminated. Full moon occurs on April 5, 2023, at 11:35 p.m.
International Space Station (ISS) Observing
There are several visible passes of ISS from St. Louis for the week of March 29. They occur during evening hours this week. The best passes for this week are listed below. Use the table below for information about these passes.
Catch ISS from St. Louis starting Wednesday, March 29
| Date | Starts | Max. altitude | Ends | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Time | Alt. | Az. | Time | Alt. | Az. | Time | Alt. | Az. | ||
| 31 Mar | -2.7 | 21:20:46 | 10 | WNW | 21:23:18 | 45 | WNW | 21:23:18 | 45 | WNW |
| 01 Apr | -3.8 | 20:32:23 | 10 | NW | 20:35:43 | 69 | NE | 20:37:05 | 32 | ESE |
| 03 Apr | -2.5 | 20:32:14 | 10 | WNW | 20:35:21 | 37 | SW | 20:37:39 | 16 | SSE |
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°.
For information about ISS flyovers and other visible satellites, visit www.heavens-above.com
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 west at 8:00 p.m. on March 29, 2023. Credit: Stellarium, EG
This week, three naked eye planets will be visible. Venus and Mars are found in the west after sunset. Mercury will become visible at the end of the week in the west after sunset. Saturn will soon be visible in the east before sunrise.
Mercury
Mercury is starting its next evening apparition. At the start of the week, it will be too low to see due to trees, buildings and twilight glare. By April 8, 2023, Mercury will be about 10° above the horizon at 8:00 p.m. Mercury will reach greatest eastern elongation on April 11, 2023.
Venus
Venus is now well into its current evening apparition. Venus will be a bright target in the west after sunset until August 2023 when it approaches inferior conjunction. This week, look for Venus in the west about 20 minutes after sunset. Venus sets at 10:21 p.m.
Mars
Mars now rises before sunset, becoming visible once it is dark. Look for it high in the west about 30 minutes after sunset. Mars sets by 2:10 a.m.
Saturn
Saturn is slowly climbing out of the Sun’s glare about 30 minutes before sunrise. For many of us, Saturn is still to low to spot due obstruction along the horizon. The ringed planet will soon return to our morning sky.
James S. McDonnell Planetarium
Night Sky Update: March 29 – April 8, 2023