This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Friday, December 9, 2022.
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.
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 February 3, join us indoors in our planetarium theater for “The Sky Tonight”. Showtime is at 7 p.m.
*** There will not be a First Friday in January 2023. ***
Observing Highlight of the Week
A Leonid meteor imaged in 2009. Image credit: Navicore.
The 2022 Geminid Meteor Shower is upon us. Often called shooting stars, meteors are space debris entering Earth’s atmosphere. Every year starting around November 19 and lasting through December 24, Earth enters a stream of debris from the asteroid 3200 Phaethon. As this debris enters Earth’s atmosphere, our skies are periodically lit up with streaks of light that signal the demise of that debris. If large enough, a meteor can become so bright its light will briefly cast shadows.
Meteor showers are annual events that are normally caused by comets. If a comet’s orbit is close enough to Earth, the debris it leaves behind will intersect Earth’s orbit producing an annual meteor shower. The Geminids are one of a few meteor showers not caused by a comet but rather is caused by an asteroid. Recently, scientists may have discovered how an asteroid can produce the debris associated with meteors. It is thought that perhaps sodium vaporizing in the asteroid could cause outgassing events that release the debris. You can learn more about this research at https://www.jpl.nasa.gov/news/fizzing-sodium-could-explain-asteroid-phaethons-cometlike-activity
Most meteor showers last several weeks but they do exhibit peak behavior. The peak date of the Geminids usually occurs on December 13/14 which is true for 2022. Increased activity starts around the 10th, but your best views will be in the early morning hours of December 14.
From a dark location, the Geminids are known to produce roughly 150 meteors per hour during peak activity. This is provided you are viewing away from light pollution and the moon phase is near new moon. This year the Moon will exhibit a waning gibbous phase with roughly 72% disk illumination. Sadly, this means the Moon will interfere with the meteor shower.
Observing meteor showers is simple. First, find a dark location and grab a chair that reclines. Next, locate the radiant of the meteor shower. The radiant is the location in the sky that meteors appear to emanate from. The reason a radiant occurs is the same reason why when driving in a snowstorm, snowflakes appear to come from a point in front of you. As the Earth moves through a stream of debris, the particles are traveling in parallel pathways. This causes them to appear to converge at a point in front of the direction Earth is traveling. The radiant of a meteor shower is not the only place you see meteors; it is just something to be aware of. Knowing where the radiant is, informs where you see meteors come from. If the radiant is low to the horizon, you will see meteors from that direction. If it is overhead, meteors will be seen in all directions moving away from the radiant. On December 13, the Geminid radiant is rising by 7:00 p.m. and it will culminate around 2:00 a.m.
If weather conditions do not permit clear views of the sky, there is another way to observe meteors. Radio telescopes can be used to detect when a meteor enters the atmosphere. Most people are unaware that they already own a radio telescope of sorts. If you have a normal radio, that is in essence a radio telescope. If this interests you, I recommend exploring these radio meteor links.
https://www.rasc.ca/sites/default/files/RadioAstronomy_NovaNotes.pdf
http://mercury.pr.erau.edu/~prcphysics/observatory/meteors.htm
https://amsmeteors.org/ams-programs/radio-observing/
The Sun and Moon
The Moon as seen from the International Space Station, on July 31, 2011.
Credit: NASA
Sunrise is at 7:07 a.m. on Friday, December 9 and sunset is at 4:39 p.m. providing us with a bit under 10 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 6:15 p.m. this week. For those with a sundial, local noon occurs around 11:53 a.m. this week.
| Day | Sunrise | Sunset |
|---|---|---|
| 2022-12-09 | 7:07 a.m. | 4:39 p.m. |
| 2022-12-10 | 7:08 a.m. | 4:39 p.m. |
| 2022-12-11 | 7:08 a.m. | 4:40 p.m. |
| 2022-12-12 | 7:09 a.m. | 4:40 p.m. |
| 2022-12-13 | 7:10 a.m. | 4:40 p.m. |
| 2022-12-14 | 7:11 a.m. | 4:40 p.m. |
| 2022-12-15 | 7:11 a.m. | 4:40 p.m. |
| 2022-12-16 | 7:12 a.m. | 4:41 p.m. |
| 2022-12-17 | 7:13 a.m. | 4:41 p.m. |
Moon
Moonrise for Friday, December 9 was at 5:44 p.m. and moonset occurs at 9:31 a.m. on the following day. Friday, December 9, the Moon will exhibit a waning gibbous phase with 97% of the lunar disk illuminated. Last quarter moon occurs on December 16, 2022, at 2:56 a.m.
International Space Station (ISS) Observing
There are several visible passes of ISS from St. Louis for the week of December 9. They occur during evening and morning hours. The best passes for this week are listed below. Use the table below for information about these passes.
Catch ISS from St. Louis starting Friday, December 9
| Date | Starts | Max. altitude | Ends | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Time | Alt. | Az. | Time | Alt. | Az. | Time | Alt. | Az. | ||
| 09 Dec | -2 | 17:05:06 | 10 | WNW | 17:08:13 | 38 | SW | 17:11:20 | 10 | SSE |
| 16 Dec | -2.2 | 06:33:44 | 10 | SSW | 06:36:53 | 40 | SE | 06:04:03 | 10 | ENE |
| 18 Dec | -3.8 | 06:33:30 | 10 | WSW | 06:36:49 | 64 | NW | 06:40:10 | 10 | NE |
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 southeast at 7:00 p.m. on December 9, 2022. Credit: Stellarium, EG
Looking south at 2:00 a.m. on December 10, 2022. Credit: Stellarium, EG.
This week, three naked eye planets are visible. Mars, Jupiter and Saturn rise before sunset and will be visible once it is dark. At the start of the week Mercury and Venus will be tough to see in the west but as the weeks ends, those with clear horizons may spot these planets low in the west after sunset.
Mercury
Mercury is climbing out of the Sun’s glare this week and should be visible at the end of the week. Mercury reaches greatest eastern elongation on December 21, 2022. As we get closer to this date, Mercury should be easy to spot. This is a good apparition for Mercury as the angle of the ecliptic is reasonably high and Mercury is brightest when coming out of superior conjunction. Keep an eye out for a bright Mercury about 30 minutes after sunset in the west.
Venus
Like Mercury, Venus is climbing out of the Sun’s glare. By the end of December, Venus should be an easy target to spot after sunset in the west. For now, those with clear western views my catch a glimpse of Venus low in the west at the end of the week. Venus is starting an evening apparition. Once high enough above the horizon, Venus will be a bright target in the west after sunset until August 2023 when it approaches inferior conjunction.
Mars
Mars now rises before sunset becoming visible once it is dark. Look for it in the east by 6:00 p.m.
Jupiter
Now past opposition, Jupiter will be visible about 30 minutes after sunset. Jupiter reaches superior conjunction on April 11, 2023. As we progress towards this date, we will see Jupiter slowly wander towards the Sun.
Saturn
Now past opposition, Saturn rises before the Sun sets. You can find this giant world in the south about 45 minutes after sunset. Saturn is still a fine target though telescopes and will be a highlight of the evening sky for the rest of the year.
James S. McDonnell Planetarium
Night Sky Update: December 9 – December 17, 2022