This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Friday, May 15, 2020.

Information updated weekly or as needed.

Times given as local St. Louis time (CDT).  For definitions of terminology used in the night sky update, click the highlighted text.

For now, star parties at the Saint Louis Science Center have been canceled due to recommendations from the CDC regarding COVID-19. All public telescope events are canceled until further notice. As conditions change, we will reevaluate and update this article once public observing events resume.

The Sun and Moon

The Moon as seen from the International Space Station, on July 31, 2011.
Credit: NASA

Sunrise is at 5:49 a.m. on Friday, May 15 and sunset is at 8:07 p.m. providing us with over 14 hours of daylight. Even after sunset, the light from the Sun will dimly illuminate our sky for almost 2 hours. This period is called twilight, which ends around 9:54 p.m. this week. For those with a sundial, solar transit or local noon occurs around 12:58 p.m. this week.

2020-05-15 5:49 a.m.8:07 p.m.
2020-05-16 5:48 a.m.8:08 p.m.
2020-05-17 5:47 a.m.8:08 p.m.
2020-05-18 5:46 a.m.8:09 p.m.
2020-05-19 5:46 a.m.8:10 p.m.
2020-05-20 5:45 a.m.8:11 p.m.
2020-05-21 5:44 a.m.8:12 p.m.
2020-05-22 5:43 a.m.8:13 p.m.
2020-05-23 5:43 a.m.8:14 p.m.

Moonrise for Friday, May 15 occurs at 2:43 p.m. and moonset will occur at 13:31 p.m. On Friday, May 15 the Moon will be exhibiting a waning crescent phase with roughly 37% of the lunar disk illuminated. New moon occurs on May 22.

International Space Station (ISS) Observing

Credit: NASA

Visible passes of ISS from St. Louis for the week of May 15 occur during morning and evening hours. The best of these occur on the morning and evening of May 18. Use the table below for information about these and other visible passes of ISS.

Catch ISS from St. Louis starting Friday, May 15

Date Starts  Max. altitude  Ends  
15 May-0.5 03:06:1110NNW 03:08:1715NNE 03:10:2210ENE
15 May-3.6 04:42:1010NW 04:45:3275NE 04:48:5310SE
15 May-3.7 21:24:0810SW 21:27:2452SE 21:30:4210ENE
15 May-1.1 23:01:4210WNW 23:04:2321NNW 23:07:0410NNE
16 May-2.5 03:54:2910NW 03:57:4443NE 04:00:5710ESE
16 May-2.9 20:36:4610SSW 20:39:4328SE 20:42:4010ENE
16 May-1.8 22:13:2510W 22:16:2731NNW 22:19:3010NE
17 May-1.6 03:06:4510NNW 03:09:4328NNE 03:12:4010E
17 May-3.1 04:43:2710WNW 04:46:3033SW 04:49:3410SSE
17 May-2.7 21:25:0910WSW 21:28:2649NW 21:31:4310NE
18 May-3.9 03:58:0548W 03:58:4562SW 04:02:0410SE
18 May-3.7 20:37:1210SW 20:40:3386NW 20:43:5610NE
18 May-0.6 22:15:3310WNW 22:17:4616NNW 22:19:5810NNE
19 May-1 21:27:0110W 21:29:4322NNW 21:32:2510NNE
20 May-1.7 20:38:4010W 20:41:4331NNW 20:44:4610NE
21 May-0.6 21:29:3110NW21:31:1013NNW 21:32:4910NNE
22 May-0.8 20:40:4810WNW 20:43:0216NNW 20:45:1710NNE

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

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, After Sunset, May 15, 2020
Credit: Stellarium, EG

Looking Southeast, 4:00 am, May 16, 2020
Credit: Stellarium, EG

This week, four naked eye planets are visible. Venus will be visible in the west just after sunset. Mars, Jupiter and Saturn are visible in the southeast about 2 hours before sunrise.


The brightest planet in the sky is visible in the west as the sun sets. Venus reached maximum elongation for its current apparition; because of this Venus will start to move towards the Sun each night as it approaches inferior conjunction on June 3, 2020. Venus will set around 10:22 p.m.


The red planet rises around 2:25 a.m. and will be high enough to see in the southeast by 3:30 a.m. Opposition for Mars occurs on October 13, 2020. As we head towards this date Mars will appear brighter and its surface will eventually be visible through a telescope.


The king of the planets is rising around 12:35 a.m. and should be visible in the southeast around 1:30 a.m. Each week you will find Jupiter rising about 20 minutes earlier than it did in the previous week.


Saturn is rising around 00:50 a.m. Like Jupiter you will need a clear sky to the southeast to catch the ring planet around 2:00 a.m. Later this year Jupiter and Saturn will reach conjunction on December 21, 2020. You can track these planets as they appear to chase one another throughout the rest of this year.

2020 Great Conjunction

This year, the planets Jupiter and Saturn will reach conjunction.  A conjunction is when two or more celestial bodies share the same right ascension.  For Jupiter and Saturn, this astronomical event only occurs every 20 years. The conjunction will occur on December 21, 2020.  You will find the two planets close together in the southwestern sky just after sunset on this date.

Comet Watch

Comet C/2020 F8 SWAN

Credit: Diego Toscan

Comet SWAN (C/2020 F8)

With what seems to be another comet let down, there is hope for comet hunters. A comet was discovered by Michael Mattiazzo searching imagery from the Solar Wind Anisotropies (SWAN) camera on the Solar and Heliospheric Observatory (SOHO). SWAN’s primary science objective has to do with monitoring the solar wind in Lyman-α light, a type of UV radiation. It also monitors sunspots and can observe comets in this same emitted wavelength of light. Learn more at

Right now, Comet SWAN is in the constellation Pisces and is rising around the same time as the Sun. Its closest approach to Earth occurred on May 12. As we go through May, Comet SWAN will move from the constellation Pisces through Triangulum, Perseus and Auriga. Unfortunately, we will be fighting morning twilight.  The best window of observation appears to be May 15 through May 19. On these dates Comet SWAN will be roughly 7° to 10° above the horizon around 4:30 a.m. To find this comet you will need a clear view of the eastern and northeastern horizon.

Currently Comet SWAN is around 5.7 magnitude, but it is predicted to reach 3rd magnitude in the last half of May. The behavior of comets is unpredictable and as such predictions of future magnitudes is never a guarantee. This said, Comet SWAN will be a comet to keep track of. There are several ways to track this comet. The two I regularly use are Stellarium and  Both will require minor set up, but they are easy to use. There is also an article available on that will show the path of Comet C/2020 F8 SWAN through June 6. 

UPDATE for C/2019 Y4 ATLAS May 15, 2020

Comet C/2019 Y4 ATLAS brightened a bit to 8.8 magnitude. Observations done with the Hubble Space Telescope have confirmed this comet is disintegrating. It looks like C/2019 Y4 ATLAS will not perform as we hoped it would. Certainly, this is a disappointment to backyard observers, but for astronomers who study comets, this is an exciting time. It is not often they are given a chance to see this process so clearly and as such it is a valuable opportunity for them. You can learn more about this at

Visit the James S. McDonnell Planetarium for more information on what’s up!

Night Sky Update: May 15-May 23, 2020