This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Saturday, December 30, 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.
Observing Highlight of the Week
Comet Hale-Bopp, photographed at Tierra del Sol in San Diego County in April 1997. Image credit: Mkfairdpm
As we look forward to 2024, there are several astronomical events worth taking note of. A solar eclipse, two lunar eclipses, the regular group of major meteors showers and two promising comets that will keep us busy throughout 2024.
For many, the total solar eclipse on April 8, 2024, is the event they are most looking forward to. While it is the best eclipse of the year, it is not the only one. An annular solar eclipse occurs on October 2, 2024, but unfortunately it is not visible in St. Louis and the path of annularity will not be visible from many places. The best views are from limited locations in southern Chile and Argentina along with a few islands and atolls in the Pacific such as Rapa Nui. There are also two lunar eclipses in 2024. The first is a penumbral lunar eclipse on March 24/25, 2024. This is visible in St. Louis however the Moon barely enters Earth’s penumbral shadow so it is unlikely observers will see any change on the lunar surface. The second lunar eclipse occurs on September 17, 2023, which will also be visible from St. Louis. It is a partial eclipse with a magnitude of 0.085 which means we will see about 3.5% of the lunar surface enter Earth’s umbral shadow. This is not the best lunar eclipse however it will still be one to watch if skies are clear.
On April 8, 2024, most of North America will see at least a partial solar eclipse. However, those that travel to a path that runs from Mexico up to Maine, will be treated to a total solar eclipse. As the path runs across Missouri, it clips the southeastern corner of the state. Totality can be seen about an hour south of St. Louis, but the best views will be found along the path running from Poplar Bluff to Cape Girardeau. We will cover the eclipse in greater detail as it approaches, but for now I recommend you visit the MO Eclipse website.
In addition to the four eclipses of 2024, the normal group of major meteors showers will be worth considering. These meteor showers are the Quadrantids in January, Lyrids in April, eta Aquarids in May, Sothern delta Aquarids in July, Perseids in August, Orionids in October, Leonids in November, Geminids in December and finally the Ursids in December. Of these nine meteor showers, the three best each year are the Quadrantids, Perseids and Geminids. Unfortunately, the Moon will interfere with all three of these due to the moon phase on the night of each shower’s peak activity. The most promising in 2024 will be the Perseids. On that night the Moon will reach its first quarter phase. This will impact the early hours of peak activity for the Perseids; however, the Moon will set before the Perseid radiant culminates. If you would like to learn more about meteor showers in general, I recommend visiting the American Meteor Society website.
What I am most excited for are a couple of comets that should become bright enough to see in St. Louis with binoculars. These comets are called 12P/Pons-Brooks and C/2023 A3 (Tsuchinshan-ATLAS).
12P/Pons-Brooks is a periodic comet that orbits the Sun every 71 years. Historically it was discovered in 1812 by French astronomer Jean-Louis Pons, however records in China show apparitions of this comet in 1385 and 1457 and a possible apparition as far back as 245 CE. It is a comet known for exhibiting outburst activity that recently has been suggested to be the product of cryovolcanic eruptions. 12P/Pons-Brooks is heading towards its next perihelion on April 21, 2024, so it should continue to increase in magnitude as it approaches this date. Peak magnitude for 12P/Pons-Brooks is expected to reach 4.2 magnitude. This is bright enough to see the comet in binoculars from an urban location. Current observations put the comet at 8.6 magnitude and its location is currently the constellation Cygnus.
The other comet to keep an eye on is C/2023 A3 (Tsuchinshan-ATLAS). This comet was discovered in early 2023 at the Purple Mountain Observatory in China and the ATLAS survey in South Africa. C/2023 A3 appears to come from the Oort cloud and preliminary observations suggest an inbound orbital period of 80,660 years. However, its orbit is hyperbolic so it is possible that its outbound trajectory could see C/2023 A3 leave the solar system.
C/2023 A3 is the comet most are looking forward to. Early predictions suggest the comet could reach a peak magnitude of -0.2 when it passes nearest to Earth on October 13, 2024. One reason why some are expecting this to be a bright comet is due to how close to the Sun it will be when at perihelion. When nearest the Sun, C/2023 A3 will be a similar distance from the Sun as Mercury is. For comets, which are big hunks of ice, being that close to the Sun can have destructive results. It is possible that C/2023 A3 could break apart before it reaches perigee in October. If it survives perihelion, there is a possibility due to forward scattering of sunlight by the comet’s dust tail, C/2023 A3’s peak magnitude could be even better than early modeling suggests.
Since its discovery in January 2023, observers have been excited for comet C/2023 A3. The last two great comets seen in the northern hemisphere are Comet Hyakutake and Comet Hale Bopp which had apparitions in 1996 and 1997 respectively. When at peak magnitude, Comet Hyakutake reached 0.0 magnitude and Comet Hale Bopp reached -1.8 magnitude. It is hopeful that C/2023 A3 could appear somewhere between these magnitudes. There is no guarantee that C/2023 A3 will be as good as these two comets were, but it will be exciting as we wait and see.
The last thing to mention about comets is predicting how bright they will be is very difficult. Often a comet that is predicted to be the next great comet will turn out to be a disappointment compared to the hype that preceded it. A very famous example of this is Comet Kohoutek. So, when you see predicted magnitude numbers remember that they are just predictions. We will have to wait and see what comet C/2023 A3 will have in store for us.
The Sun and Moon
The Moon as seen from the International Space Station, on July 31, 2011.
Credit: NASA
Sun
Sunrise is at 7:18 a.m. on Saturday, December 30 and sunset is at 4:48 p.m. providing us with roughly 9 hours and 30 minutes of daylight this week. 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 6:24 p.m. this week. For those with a sundial, local noon occurs around 12:02 p.m. this week.
| Day | Sunrise | Sunset | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 30-Dec | 7:18 a.m. | 4:48 p.m. | ||||||||||
| 31-Dec | 7:18 a.m. | 4:49 p.m. | ||||||||||
| 1-Jan | 7:18 a.m. | 4:50 p.m. | ||||||||||
| 2-Jan | 7:19 a.m. | 4:51 p.m. | ||||||||||
| 3-Jan | 7:19 a.m. | 4:52 p.m. | ||||||||||
| 4-Jan | 7:19 a.m. | 4:52 p.m. | ||||||||||
| 5-Jan | 7:19 a.m. | 4:53 p.m. | ||||||||||
| 6-Jan | 7:19 a.m. | 4:54 p.m. | ||||||||||
| 7-Jan | 7:19 a.m. | 4:55 p.m. |
Moon
Moonrise for Saturday, December 30 was at 8:24 p.m. and moonset occurred at 10:31 a.m. the following day. On Saturday, December 30, the Moon will exhibit a waning gibbous phase with roughly 86% disk illumination. By the end of the week the Moon will exhibit a waning crescent phase with 15% disk illumination. Last quarter moon occurs on January 3, 2024, at 9:31 p.m.
International Space Station (ISS) Observing
There are several visible passes of ISS from St. Louis for the week of December 30. They occur 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.
Catch ISS from St. Louis starting Saturday, December 30, 2023
| Date | Starts | Max. altitude | Ends | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Time | Alt. | Az. | Time | Alt. | Az. | Time | Alt. | Az. | ||
| 02 Jan | -2.8 | 6:07:06 | 19 | NNW | 6:09:11 | 42 | NNE | 6:12:24 | 10 | ESE |
| 04 Jan | -3.7 | 6:07:08 | 26 | WNW | 6:08:48 | 66 | SW | 6:12:07 | 10 | SE |
| 05 Jan | -3.1 | 5:20:39 | 55 | E | 5:20:39 | 55 | E | 5:23:27 | 10 | ESE |
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 5:30 p.m. on January 1, 2024. Credit: Stellarium, EG
Looking southeast at 6:00 a.m. on January 2, 2024. Credit: Stellarium, EG
This week, three naked eye planets will be visible. Saturn and Jupiter are visible in the south once it is dark. Venus will be easy to find in the southeast before sunrise.
Venus
Venus rises this week around 4:29 a.m. It will be easy to spot for most by 6:00 a.m. If you have a clear view of the planet, telescopes will reveal a gibbous phase with roughly 78.3% disk illumination. Now that Venus is past dichotomy, it is beginning to head back towards the Sun from our perspective. As this continues, Venus’s disk illumination will increase as it heads towards superior conjunction on June 4, 2024.
Jupiter
Jupiter has passed opposition and as such it will rise before the Sun sets. Jupiter will be easy to spot in the southt once it is dark outside. Jupiter will set around 2:08 a.m.
Saturn
Start looking for Saturn in the south about 30 minutes after sunset. Saturn will set around 8:59 p.m. Our window to see Saturn is starting to close as it is approaching solar conjunction on February 28, 2024. As we approach this date Saturn will be found lower to the horizon each day eventually being lost to the Sun’s glare near the end of February.
James S. McDonnell Planetarium
Night Sky Update: December 30, 2023-January 7, 2024