This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Friday, October 29, 2021.
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
With the changing recommendations from the CDC regarding COVID-19, conversations regarding the return of star parties at the Saint Louis Science Center have begun. We are close to bringing back our public telescope viewings, but a few details still need to be worked out. We will post future updates as we learn more about when we can bring back telescope viewings.
Observing Highlight of the Week
Messier 45 is an open star cluster visible in the constellation Taurus the Bull. You will find it rising in the east not long after sunset. Image credit: NASA, ESA, AURA/Caltech, Palomar Observatory
We will end October by returning to the Pleiades star cluster which we covered earlier this month. I wanted to return to the Pleiades because there are many topics that make this star cluster fascinating. I am including it this week because it has a connection to much of what happens this time of year. In ancient times, astronomers would look to the sky for many reasons. Early efforts to understand the night sky would lead to astronomical objects being observed as gods, deities or other mythical creatures. This is called astrolatry which often pertained to objects like the Sun, Moon and planets. In some cases, other astronomical phenomena such as an eclipse or the occurrence of an eclipse would also be attributed to mythical happenings. In time, ancient astronomers started to see predictability in the motions of these astronomical objects. This predictability would inform a deeper understanding of the seasons, time and later would be integral to early navigation techniques.
As this knowledge developed, complex systems would come about that allowed ancient astronomers to track and predict astronomical occurrences. The calendars we use today are the product of these advancements. Before modern solar calendars became the standard, the cycles of the Moon and the passage of stars at night were the standard timekeepers. Stellar calendars like the Egyptian decan system are an example of how ancient astronomers would develop a deeper connection to the annual shift of the sky.
The Egyptian decan system consisted of 36 stars or constellations chosen to mark the progression of hours at night. As a new decan would rise a new hour started. After a 10-day period, a decan would shift one hour as the year progressed. The 36 decans combined with the 10-day cycle would represent a calendar of 360 days with an extra 5 added to sync the calendar with the heliacal rising of the decan star Sirius. The Egyptians discovered that the heliacal rising of Sirius occurred roughly every 365 days. The heliacal rising of Sirius was then used as the event that marked the start of a new year which coincided with the annual flood of the Nile River. The first records of the decan system are found on coffin lids from the 9th dynasty which starts around 2160 BCE. The only identified decans are the star Sirius, Orion and the Foreleg which today we call the Big Dipper. There have been efforts to identify the remaining decans but that has yet to be achieved.
Scholars still debate on what the purpose of decan system was. Is it a complex system based on advanced scientific knowledge of the sky used with secular purpose? Or was it primarily used to monitor, track and set the times of cultural or religious traditions? One mechanic of the decan system was each decan disappeared for a period of 70-days. This 70-day period was supposed to start with the acronical setting of a decan. The disappearance occurred because the decan appeared to near the Sun for 70-days and as such was not visible at night. It is no coincidence that much of what is known about the decan system is found in burials. The well-known tradition of Egyptian mummification is also a process that lasted 70 days. It is likely that the Egyptian decan system was used for both scientific and cultural reasons. The answer to this debate may never be found, but the decan system stands as a great example of how humanity’s curiosity and desire to understand the changing world led to great innovations. One such contribution of the decan system is the idea of a 24-hour day.
This now brings us to the Pleiades. Cultures around the world used the Pleiades in similar ways as the Egyptians used the decans. One such example is the Celtic culture of Europe. This Celts first appeared around 1200 BCE. Evidence of the Celts is most prominent in England and Ireland where today you can still find traces of the culture in language and traditions. One of the most famous traditions rooted in Celtic culture is Halloween. Traditionally called Samhain, this tradition is determined by the cycle of the seasons. Samhain had a deep connection to the cultural traditions of the Celts but astronomically it represented the start of the dark half of the year. Samhain or Halloween is/was a cross-quarter day. Today, cross-quarter days are the halfway point between seasons. In Ancient times, they were the start of a season but due to modern observations we see them as the halfway point between an equinox and a solstice. Due to modern calendars, the cross-quarter day occurring between northern fall and winter, now occurs around November 7. For the Celts, it was on Samhain. The festival of Samhain would start when the Pleiades reached its culminating point. An object reaches culmination when it is seen at its highest altitude for the night. For the Celts, Samhain represented a day steeped in cultural tradition. Like other modern traditions with ancient origins, Samhain or Halloween is rooted in astronomical knowledge developed thousands of years ago.
Halloween is one of many traditions with a connection to the Pleiades. So, this Halloween, after all the treats are collected and tricks played, we can go outside and enjoy the sight of one of the true astronomical gems we see this time of year. Whether you are enjoying its beauty or delving into its more complex nuances, remember that cultures around the world throughout time relied on this cluster for secular and sacred reasons. Exploring these is a great way to expand your interest and connection to the night sky.
The Sun and Moon
The Moon as seen from the International Space Station, on July 31, 2011.
Credit: NASA
Sunrise is at 7:25 a.m. on Friday, October 29 and sunset is at 6:04 p.m. providing us with about 10 hours and 40 minutes of daylight. Even after sunset, the light from the Sun will dimly illuminate our sky for roughly 1 hour and 30 minutes. This period is called twilight, which ends around 7:34 p.m. this week. For those with a sundial, local noon occurs around 12:44 p.m. this week.
| Day | Sunrise | Sunset |
|---|---|---|
| 2021-10-29 | 7:25 a.m. | 6:04 p.m. |
| 2021-10-30 | 7:26 a.m. | 6:02 p.m. |
| 2021-10-31 | 7:27 a.m. | 6:01 p.m. |
| 2021-11-01 | 7:28 a.m. | 6:00 p.m. |
| 2021-11-02 | 7:29 a.m. | 5:59 p.m. |
| 2021-11-03 | 7:30 a.m. | 5:58 p.m. |
| 2021-11-04 | 7:31 a.m. | 5:57 p.m. |
| 2021-11-05 | 7:32 a.m. | 5:56 p.m. |
| 2021-11-06 | 7:33 a.m. | 5:55 p.m. |
Moon
Moonrise for Friday, October 29 occurred at 12:11 a.m. and moonset will occur at 3:04 p.m. On Friday, October 29 the Moon will exhibit a waning crescent phase with about 39% of the lunar disk illuminated. New moon occurs on November 4 at 4:15 p.m.
International Space Station (ISS) Observing
Visible passes of ISS from St. Louis for the week of October 29 occur during morning hours. The best pass this week occurs on the morning of November 5. Use the table below for information about this and other visible passes this week.
Catch ISS from St. Louis starting Friday, October 29
| Date | Starts | Max. altitude | Ends | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Time | Alt. | Az. | Time | Alt. | Az. | Time | Alt. | Az. | ||
| 03 Nov | -1.2 | 06:28:12 | 10 | NNW | 06:29:58 | 14 | NNE | 06:31:46 | 10 | NE |
| 05 Nov | -1.8 | 06:29:46 | 10 | NNW | 06:32:29 | 24 | NNE | 06:35:17 | 10 | E |
| 06 Nov | -1.5 | 05:44:28 | 17 | NNE | 05:44:56 | 17 | NNE | 05:47:18 | 10 | ENE |
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 South, at 6:30 p.m. October 30, 2021. Credit: Stellarium, EG
Looking east, at 6:50 am, October 31, 2021. Credit: Stellarium, EG
This week, three naked eye planets are visible. Venus can be found in the southwest after sunset. Jupiter and Saturn can be found in the southeast after sunset. Mercury is visible in the east before sunrise.
Mercury
Mercury reached maximum elongation for its current morning apparition on October 25, 2021. This means each morning Mercury will appear closer to the Sun each day. Fleeting views of Mercury are still possible about 30 minutes before sunrise. As the week progresses, Mercury will appear lower to the horizon each morning. Mercury reaches Superior conjunction on November 28, 2021. After this date, Mercury will climb out of the Sun’s glare in the west after sunset.
Venus
Venus is well into another evening apparition. By 6:22 p.m., Venus will be about 16° above the southwestern horizon. Venus will set at 8:22 p.m. Venus reached maximum eastern elongation October 29, 2021. Venus is now headed back towards the Sun as it approaches inferior conjunction on January 8, 2022.
Mars
The red planet has not been visible for several weeks now. The previous apparition of Mars has ended. But for those itching to see Mars again, you are in luck as the next apparition of Mars begins in November 2021. Mars will climb out of the Sun’s glare eventually becoming visible just before sunrise. The next Mars apparition is expected to begin around November 14, 2021, when Mars will appear far enough from the Sun for safe viewing.
Jupiter
Jupiter has passed opposition and as such will be visible about 30 minutes after sunset. Look for Jupiter in the south as it starts to darken outside. Jupiter sets at 1:16 a.m. tomorrow morning and will set about 30 minutes earlier each week. Jupiter reaches superior conjunction on March 5, 2022. This means we can count on seeing Jupiter in the southern skies for the rest of this year and well into 2022.
Saturn
Saturn is past opposition which means it will be visible about 30 minutes after sunset. Right now, it can be found in the south after sunset, but as we continue through the year, Saturn will set about 30 minutes earlier each night. Saturn sets at 11:55 p.m. Saturn will reach superior conjunction on February 4, 2022
Uranus
Uranus will reach opposition on November 5, 2021, at 0 hrs. UT. For us in St. Louis, that translates to 19:00 or 7:00 p.m. CDT. When near opposition, Uranus can be seen naked eye under dark skies. In St. Louis you will need binoculars to spot this ice giant. Uranus rises at 6:14 p.m. and will be easily found by 9:00 pm in the east in the constellation Aries.
James S. McDonnell Planetarium
Night Sky Update: October 29 – November 6, 2021