This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Friday, May 01, 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 6:12 a.m. on Friday, May 1 and sunset is at 7:47 p.m. providing us with about 13.5 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 9:35 p.m. this week. For those with a sundial, solar transit or local noon occurs around 12:58 p.m. this week.

2020-05-01 6:03 a.m.7:54 p.m.
2020-05-02 6:02 a.m.7:55 p.m.
2020-05-03 6:01 a.m.7:56 p.m.
2020-05-04 6:00 a.m.7:57 p.m.
2020-05-05 5:59 a.m.7:58 p.m.
2020-05-06 5:58 a.m.7:58 p.m.
2020-05-07 5:56 a.m.7:59 p.m.
2020-05-08 5:55 a.m.8:00 p.m.
2020-05-09 5:54 a.m.8:01 p.m.

Moonrise for Friday, May 1 occurs at 1:11 p.m. and moonset will occur at 2:50 a.m. on the following day. On Friday, May 1 the Moon will be exhibiting a waxing gibbous phase with roughly 59% of the lunar disk illuminated. Full moon occurs on May 7 at 5:45 a.m. May’s full moon is often called the Full Flower Moon.

International Space Station (ISS) Observing

Credit: NASA

Visible passes of ISS from St. Louis for the week of May 1 occur during morning hours. The best of these occur on the mornings of May 1, 2 and 5. Use the table below for information about these and other visible passes of ISS.

Catch ISS from St. Louis starting Friday, May 1

DateStartsMax. altitudeEnds
01 May-2.3 04:32:3523WNW 04:33:4529NNW 04:36:4510NNE
02 May-2.6 03:46:3239N 03:46:3239N 03:49:0910NE
03 May-1 03:00:2519NE 03:00:2519NE 03:01:2910NE
03 May-1.3 04:33:2111WNW 04:35:2016NNW 04:37:2810NNE
04 May-1.703:47:1121NNW 03:47:2021NNW 03:49:5910NNE
05 May-1.1 03:00:5920NNE 03:00:5920NNE 03:02:2510NNE
06 May-1 03:47:4011NW 03:48:5813NNW 03:50:3010NNE
07 May-0.9 03:01:2215N 03:01:2215N03:03:0310NNE

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, 30 Minutes After Sunset, May 1, 2020
Credit: Stellarium, EG

Looking Southeast, 4:00 am, May 2, 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 11:10 p.m.


The red planet rises around 2:51 a.m. and will be high enough to see in the southeast by 4:00 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 1:25 a.m. and should be visible in the southeast around 2:30 a.m. Each week you will find Jupiter rising about 30 minutes earlier than it did in the previous week.


Saturn is rising around 1:41 a.m. Like Jupiter you will need a clear sky to the southeast to catch the ring planet around 2:30 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

HST image of disintegrating C/2019 Y4 ATLAS

Credit: NASA, ESA, STScI and D. Jewitt (UCLA)

UPDATE for C/2019 Y4 ATLAS May 1, 2020

Discovered in 2019, Comet C/2019 Y4 ATLAS quickly caught the attention of scientists and observers as it appeared this comet might become one of the next bright comets. It was discovered in images from a robotic telescope survey called ATLAS (Asteroid Terrestrial-impact Last Alert System).  This instrument consists of two 0.5-meter telescopes that each clear night observes a quarter of the observable sky looking for moving objects. The intention is to identify Near-Earth Objects (NEOs). Currently this survey has discovered 430 Near-Earth Asteroids, 44 Potentially Hazardous Asteroids, 37 Comets and 5464 Supernovae.  Supernovae are not what would be considered moving objects but are a bonus science objective the program contributes to.

Sadly, in early April astronomers noted a distinct change in the comet’s appearance. Initially C/2019 Y4 ATLAS’s core looked more compact until April when it has changed to a more elongated fuzzy appearance.  This suggested the comet has fragmented which was later confirmed.

Comet C/2019 Y4 ATLAS currently appears as a  9.5 magnitude object. Sadly, the comet continues to break apart signaling it is disintegrating. Observations done with the Hubble Space Telescope have confirmed this. 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

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 Cetus and is rising around the same time as the Sun. As we head into May, Comet SWAN will move into the constellation Pisces starting our best chance to catch it before sunrise. As we head into the last half of May, Comet SWAN will head north passing through the constellations 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 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 5.2 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.

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

Night Sky Update: May 1-May 9, 2020