This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Friday, October 2, 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.

Public Telescope Viewings

Star parties at the Saint Louis Science Center have temporarily 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.

Observing Highlight of the Week

Moon and Mars on October 2 and Simulated view of Mars on October 6, 2020 at 11:00 pm
Credit: Stellarium, EG

This week we will highlight the planet Mars. In the next couple weeks, a few significant events related to Mars will occur. These events include a conjunction, close approach to Earth and opposition. One of these events will be visible to the unaided eye. The other two will be best viewed through telescopes.

First on October 2, Mars and the Moon will be in conjunction. You may remember at the beginning of September, something similar occurred. October’s conjunction will not see Mars and the Moon as close as we saw them in September, but on October 2, the Moon and Mars will be separated by about 1°. On the same night around 1:22 a.m. the Moon will occult a 4.45 magnitude star named 106 Psc. It will be best to use a telescope to see this occultation, but binoculars should work as well. 106 Psc is a binary star that will have an orange color.

Also, this week, Earth and Mars will be at their closest on October 6 separated by only 38.5 million miles. This close approach occurs approximately every 26 months which is connected to the opposition of Mars. Opposition is when Mars appears its brightest due to the opposition effect. During opposition, Mars is at the anti-solar point in the sky during which time shadows are hidden by the object casting them. This results in more sunlit areas visible and less shadowed areas resulting in the Opposition effect. This is the same reason why the Moon looks brighter during full moon. The next Mars opposition occurs on October 13, 2020. The closest approach and opposition of Mars can be separated by as much as 8.5 days. During close approach is when Mars appears its largest. On October 6, Mars will have an angular diameter of 22.6 arc seconds compared to 6 arc seconds at the beginning of the current apparition.

There is a 15/17-year cycle of this behavior that sees the close approach distance varying from roughly 34 million miles to 63 million miles. 2018 was the closest approach of the two planets for the current 17-year cycle and 2027 will be the most distant separation of this close approach behavior. The variance in distance depends on when Mars is at perihelion (closest point to Sun). If opposition occurs near the Martian perihelion, then the close approach will be around 35 million miles. This next occurs in 2035.

In 2003, we experienced the best opposition of Mars for some time. During this perihelic opposition Earth and Mars were only separated by 34.65 million miles. The next opposition that is close to this occurs on September 1, 2082 but it will not be as close as it the one in 2003. To see Earth and Mars closer than the 2003 opposition, we must wait until the opposition on August 29, 2287.

The benefit of Mars opposition for us is what we see. To the unaided eye, Mars will appear brighter than any star at night and will only be fainter than the Moon and Venus. Through a telescope, we can see the surface of Mars. Views of the Martian surface have been possible for some time, but they have been getting better as we approach opposition. Everything you could ever want to know about the 2020-2021 apparition of Mars can be found here.

What to expect when looking at Mars through a telescope will be a reddish orange disk with darker or lighter areas. These dark and light areas a referred to as albedo features. What is visible will vary due to Mars’s axial rotation and weather and observing conditions on Earth. There is nuance to observing Mars, so do not be surprised if at first not much detail stands out to you. It takes practice and ideal conditions to get the most out of views of Mars.

The Sun and Moon


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

Sunrise is at 6:58 a.m. on Friday, October 2 and sunset is at 6:41 p.m. providing us with about 11.6 hours of daylight. Even after sunset, the light from the Sun will dimly illuminate our sky for about 1 hour and 30 minutes. This period is called twilight, which ends around 8:10 p.m. this week. For those with a sundial, local noon occurs around 12:50 p.m. this week.

DaySunriseSunset
2020-10-02 6:58 a.m.6:41 p.m.
2020-10-03 6:59 a.m.6:40 p.m.
2020-10-04 7:00 a.m.6:38 p.m.
2020-10-05 7:01 a.m.6:37 p.m.
2020-10-06 7:02 a.m.6:35 p.m.
2020-10-07 7:03 a.m.6:34 p.m.
2020-10-08 7:04 a.m.6:32 p.m.
2020-10-09 7:05 a.m.6:31 p.m.
2020-10-10 7:06 a.m.6:29 p.m.

Moon 

Moonrise for Friday, October 2 occurs at 7:28 p.m. and moonset will occur at 8:28 a.m. on the following day. On Friday, October 2 the Moon will exhibit a waning gibbous phase with about 99% of the lunar disk illuminated. last quarter moon occurs on October 9 at 7:40 p.m.

International Space Station (ISS) Observing

Credit: NASA

Visible passes of ISS from St. Louis for the week of October 2 occur during evening hours. The best passes this week occur on October 3, 5 and 6. Use the table below for information about this and other visible passes this week.

Catch ISS from St. Louis starting Friday, October 2

Date Starts  Max. altitude  Ends  
TimeAlt.Az.TimeAlt.Az.TimeAlt.Az.
02 Oct-1.6 19:31:1710NNW19:33:2816NNE 19:35:1012NE
02 Oct-0.8 21:07:2110NW 21:08:0816NW 21:08:0816NW
03 Oct-2.9 20:20:0610NW 20:22:4842N 20:22:4842N
04 Oct-2.7 19:32:5610NW 19:35:5930NNE 19:37:3320ENE
04 Oct-0.6 21:09:4710WNW 21:10:3215W 21:10:3215W
05 Oct-3.1 20:22:1410WNW 20:25:2352SW 20:25:2352SW
06 Oct-3.8 19:34:5010NW 19:38:1385NE 19:40:2021SE
07 Oct-1.2 20:25:0910W 20:27:2217SW 20:28:2914SSW
08 Oct-1.9 19:37:1210WNW 19:40:1028SW 19:43:0610SSE

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:

http://www.jpl.nasa.gov/

The Visible Planets


Looking Southeast, at 8:30 pm, October 2, 2020
Credit: Stellarium, EG


Looking East, 4:30 am, October 3, 2020
Credit: Stellarium, EG

This week, four naked eye planets are visible. Jupiter and Saturn rise before sunset. Look for them in the south once it is dark. Mars rises in the evening and will be best seen around midnight. Venus can be found in the eastern sky before sunrise.

For those tracking Jupiter and Saturn as they approach their great conjunction later this year, the two gas giants currently appear about 7.1° apart in the sky. From now until December 21, Jupiter will appear closer to Saturn each night.

Venus

Venus is well into another morning apparition. After months of seeing Venus in the west after sunset Venus is now visible in the east before sunrise. Venus rises at 3:43 a.m. and will be easily seen by 4:30 a.m. Venus remains a morning object until March 26, 2021 when it reaches superior conjunction. Since Venus has passed greatest western elongation, it will start to exhibit a gibbous phase. On the morning of October 3, at 4:30 a.m. you will find the planet Venus in a close pairing with the star Regulus. This is the brightest stars in the constellation Leo

Mars

The red planet rises around 7:28 p.m. and will be high enough to see in the east by 8:30 p.m. Opposition for Mars occurs on October 13, 2020. As we head towards this date Mars will appear brighter and larger through a telescope improving surface details. Surface features are already visible when viewing conditions are favorable. Current apparent brightness of Mars is -2.5 magnitude. At this magnitude Mars appears brighter than Jupiter.

Jupiter

Look for Jupiter in the southeast about 30 minutes after sunset. Jupiter will set at 12:14 a.m. Those with a telescope can enjoy views of Jupiter’s cloud features and the Great Red Spot when it is pointed towards Earth.

Saturn

Look for the ringed planet in the southeast about 30 minutes after sunset. Saturn sets at 12:51 a.m. For those with a telescope keep track of the orientation of Saturn’s rings. Since Saturn is tilted on its rotational axis, we cross the plane of Saturn’s ring every 13 to 15 years.  We are headed towards another ring plane crossing on March 23, 2025. Over the next five years you will notice Saturn’s rings will gradually incline towards an edge on appearance.

Uranus

Uranus is not a planet we normally include in this section. Even at its dimmest, the giant planet does hover within naked eye visibility. That said, it is so close to the visible limit of the human eye it just is not reality for most of us to hope to see Uranus without the aid of binoculars or a telescope.

Like other planets, when at opposition, Uranus will appear brighter than it normally does. As we approach opposition with Uranus it will shift from a visual magnitude of 5.9 to 5.7. That extra bump in magnitude makes all the difference as it is now easy to see in binoculars. The current magnitude for Uranus is 5.7. Uranus will reach opposition on October 31, so grab those binoculars and try to spot the 3rd largest planet in our solar system. You can find a finder chart for Uranus here

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 occurs every 20 years. The conjunction occurs on December 21, 2020.  You will find the two planets close together in the southwest just after sunset on this date.

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

Night Sky Update: October 2-October 10, 2020