This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Saturday, August 26, 2023.
Information updated weekly or as needed.
Times given as local St. Louis time which is Central Daylight Time (CDT). 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.
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 September 1 , join us indoors in our planetarium theater for “The Sky Tonight”. Showtime is at 7 p.m. There is no First Friday event in July.
Observing Highlight of the Week
The position of C/2023 P1 (Nishimura) from August 27, 2023 to September 8, 2023. Map created using Stellarium. The image of C/2023 P1 (Nishimura) was taken on August 15, 2023. Image credit: Dan Bartlett.
On August 11, 2023, amateur astronomer Hideo Nishimura discovered a new 11th magnitude comet in the constellation Gemini. Since its discovery, the comet now named C/2023 P1 (Nishimura) has brightened to 7.8 magnitude as it continues to make its closest approach to the Sun.
C/2023 P1 (Nishimura) was originally thought to be a hyperbolic comet indicating it came from a distant region of the solar system called the Oort Cloud. Most of the time, comets with hyperbolic trajectories are ejected from the solar system after perihelion due to their eccentric orbits. With an ever-increasing number of observations, it looks like C/2023 P1 (Nishimura) could be a periodic comet. Not enough is known about the comet to say for sure but as more time passes, scientists will be able to better model the comet’s orbit.
As of August 27, 2023, C/2023 P1 (Nishimura) is in the constellation Cancer. Over the next few weeks, the comet will pass through the constellations Cancer, Leo and Virgo as it heads towards perihelion on September 17, 2023. With current magnitude estimates of 8.8 to 7.7, C/2023 P1 (Nishimura) is within binocular visibility for those with dark skies. The comet is predicted to brighten to 3rd magnitude putting in the realm of naked eye visibility. While this prediction is very promising, it is impossible to know how the comet will behave.
Our best chance to find C/2023 P1 (Nishimura) will be from now until September 13, 2023. After this date, the comet will appear too near the Sun as it heads towards perihelion. When at perihelion, C/2023 P1 (Nishimura) will only be roughly 0.23 AU from the Sun. Because of this, it is unknown if the comet will survive. If the comet survives its perihelion, it will begin to speed away from the Sun, moving through the constellation Virgo. As it heads away from the Sun, C/2023 P1 (Nishimura) will continue to fade eventually making it difficult to see by mid-October.
To see C/2023 P1 (Nishimura), you need to look east around 5:30 a.m. At this time, the comet will appear roughly 22° above the horizon. As each day passes, the comet will be seen lower to the horizon. After perihelion, C/2023 P1 (Nishimura) shifts to early evening visibility. Unfortunately, it will be very low to the horizon just after sunset. So, it is unlikely the comet will be visible from St. Louis after perihelion.
As the weeks pass, we will update information about C/2023 P1 (Nishimura) as needed. From light polluted skies, a telescope will be needed to spot the comet, but as it continues to brighten, it should become a nice target for binocular views.
The Sun and Moon
The Moon as seen from the International Space Station, on July 31, 2011.
Credit: NASA
Sun
Sunrise is at 6:24 a.m. on Saturday, August 26 and sunset is at 7:40 p.m. providing us with less than 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 9:15 p.m. this week. For those with a sundial, local noon occurs around 1:02 p.m. this week.
| Day | Sunrise | Sunset | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 26-Aug | 6:24 a.m. | 7:40 p.m. | ||||||||||
| 27-Aug | 6:25 a.m. | 7:38 p.m. | ||||||||||
| 28-Aug | 6:26 a.m. | 7:37 p.m. | ||||||||||
| 29-Aug | 6:27 a.m. | 7:36 p.m. | ||||||||||
| 30-Aug | 6:28 a.m. | 7:34 p.m. | ||||||||||
| 31-Aug | 6:29 a.m. | 7:33 p.m. | ||||||||||
| 1-Sep | 6:30 a.m. | 7:31 p.m. | ||||||||||
| 2-Sep | 6:31 a.m. | 7:29 p.m. | ||||||||||
| 3-Sep | 6:32 a.m. | 7:28 p.m. |
Moon
Moonrise for Saturday, August 26 was at 4:47 p.m. and moonset occurs at 6:11 p.m. On Saturday, August 26, the Moon will exhibit a waxing gibbous phase with 77% disk illumination. Full moon occurs on August 30, 2023, at 8:36 p.m. This is the second full moon of August which is defined as a monthly blue moon.
Blue moons are no different than any other full moon and they will not appear blue. The cycle of moon phases was once used to keep time. Our calendar month is no longer a match to this cycle which is what allows there to be two full moons in a month every couple of years.
International Space Station (ISS) Observing
There are several visible passes of ISS from St. Louis for the week of August 26. They occur during morning hours. Use the table below for information about these passes.
Catch ISS from St. Louis starting Saturday, August 26
| Date | Starts | Max. altitude | Ends | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Time | Alt. | Az. | Time | Alt. | Az. | Time | Alt. | Az. | ||
| 27 Aug | -1.2 | 5:34:50 | 10 | NW | 5:36:36 | 13 | NNW | 5:38:22 | 10 | NNE |
| 28 Aug | -1.6 | 4:47:18 | 17 | NW | 4:47:59 | 17 | NNW | 4:50:19 | 10 | NNE |
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 southeast at 11:30 p.m. on August 26, 2023. Credit: Stellarium, EG
Looking southeast at 5:30 a.m. on August 27, 2023. Credit: Stellarium, EG
This week, four naked eye planets will be visible. Mars is still visible in the west about 30 minutes after sunset. It will be low so twilight will make spotting Mars challenging. Saturn and Jupiter will be easy to find but you will have to go out in the late evening hours to spot them. Saturn will be in the southeast around 9:30 p.m., while Jupiter will be in the east by 12:00 a.m. Lastly, Venus has started a new morning apparition. Early birds should be on the look out for the bright planet by 5:30 a.m. in the east.
Venus
Venus’s next morning apparition has begun. To find Venus, look east around 5:30 a.m. It will still be low so trees and buildings will make spotting the planet difficult. If you have a clear view of the planet, binoculars will reveal a thin crescent phase with roughly 7% disk illumination. If you attempt to see this, be careful as the Sun will rise soon after Venus does.
Mars
Mars now rises before sunset, becoming visible once it is dark. Look for it in the west about 30 minutes after sunset. Mars sets at 8:42 p.m.
Jupiter
Jupiter rises at 10:43 p.m. About one hour after Jupiter rises, it should be easy to spot. Jupiter will rise about 20 minutes earlier each week.
Saturn
Saturn rises at 8:44 p.m. Start looking for Saturn about 30 minutes after it rises. If you have lots of trees or buildings, you may have to wait an hour or so after it rises before it will be visible. Saturn reaches opposition on August 27, 2023.
James S. McDonnell Planetarium
Night Sky Update: August 26-September 3, 2023