This is the Saint Louis Science Center’s NIGHT SKY UPDATE for the week of Friday, March 12, 2021.

Information updated weekly or as needed.

Times given as local St. Louis time which is Central Standard Time (CST) until March 14 when we switch to Daylight Saving 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 -6 hours from UT when CST and -5 hours when CDT.

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

22° Halo around the Sun
Credit: Eric Gustafson

On March 20, 2021 at 4:37 a.m. the Sun’s apparent path will cross the celestial equator at its ascending node. This day is called the Vernal Equinox and it marks the start of astronomical spring. After March 20, the Sun will climb higher in the sky each day. This results in longer daytime hours and shorter nighttime hours. This behavior will continue as we head towards the summer solstice in June.

Earth’s axial tilt is the reason the Sun appears to get higher in the sky each day as we move towards summer. Earth’s axis of rotation is tilted 23.5° with respect to our orbital plane. As we revolve around the Sun this tilt causes the northern and southern hemispheres to have an annual variance in exposure to direct sunlight. This drives our seasonal fluctuations in temperature and weather. Spring and summer are the warmer seasons as the Sun appears to climb higher in the sky increasing hours of daytime. Fall and winter are the cooler seasons as the Sun appears lower in the sky leading to shorter hours of daytime.

Ancient astronomers learned to track this seasonal behavior of the Sun. They learned to predict seasonal changes assisting our transition to agrarian based societies. Knowledge of the seasons brought consistency and predictability to life. Many ancient cultures built structures or used the natural landscape to keep track of the Sun’s apparent behavior. A great example of this can be found at Cahokia Mounds State Historic Site where they recreated a structure called Woodhenge. In your backyard you can also track this behavior by watching how shadows change. The best way to do this is place a gnomon in the ground and check the length of the shadow each at local noon. The length of this shadow will change as we go through the seasons.

Another result of the Sun’s increasing altitude each day is the start of our stormy season. As the Sun climbs higher in the sky, we have more direct exposure to sunlight. This dumps more energy into the atmosphere which helps promote the conditions that can lead to sever storms. Often, before these storms arrive there is an outflow from the top of the storm cells that can produce cirrus clouds. These are high altitude clouds that are often comprised of ice crystals. When sunlight is refracted through these ice crystals various atmospheric optics occur. A common example is a solar or lunar halo. Halos can form any time of the year, but they are often precursors to these storms.

The Sun and Moon


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

Sunrise is at 6:17 a.m. on Friday, March 12 and sunset is at 6:06 p.m. providing us with roughly 12 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 7:34 p.m. this week. For those with a sundial, local noon occurs around 12:11 p.m. this week.

DaySunriseSunset
2021-03-12 6:17 a.m.6:06 p.m.
2021-03-136:15 a.m.6:07 p.m.
2021-03-14 7:13 a.m.7:08 p.m.
2021-03-15 7:12 a.m.7:09 p.m.
2021-03-16 7:10 a.m.7:09 p.m.
2021-03-17 7:09 a.m.7:10 p.m.
2021-03-18 7:07 a.m.7:11 p.m.
2021-03-19 7:06 a.m.7:12 p.m.
2021-03-20 7:04 a.m.7:13 p.m.

Moon 

Moonrise for Friday, March 12 occurs at 6:18 a.m. and moonset will occur at 5:28 p.m. On Friday, March 12 the Moon will be near new moon with 0% of the lunar disk visible. New moon occurs on March 13 at 4:21 a.m.

International Space Station (ISS) Observing

Credit: NASA

Visible passes of ISS from St. Louis for the week of March 12 occur during morning and evening hours. The best passes this week occur on the evenings of March 17 and 20. Use the table below for information about these and other visible passes this week.

Catch ISS from St. Louis starting Friday, March 12

DateStartsMax. altitudeEnds
TimeAlt.Az.TimeAlt.Az.TimeAlt.Az.
13 Mar-2.4 04:18:0337ESE 04:18:0337ESE04:20:1210SE
14 Mar-2.1 06:06:2518SW 06:06:2518SW 06:08:2210S
16 Mar-1.7 21:10:0010SW 21:11:2724SW 21:11:2724SW
17 Mar-3.6 20:22:4110SW 20:25:5753SE 20:26:5936E
18 Mar-2.719:35:3910SSW 19:38:3729SE 19:41:3510ENE
18 Mar-2 21:12:2110W 21:15:2130NNW 21:15:2130NNW
19 Mar-2.8 20:24:3610WSW 20:27:5248NW 20:30:2915NE
20 Mar-3.7 19:37:0410SW 19:40:2683NW 19:43:4810NE

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 West, at 7:00 pm, March 12, 2021
Credit: Stellarium, EG, 

Looking East Southeast, at 5:40 am, March 13, 2021
Credit: Stellarium, EG 

This week, three naked eye planets are visible. Mars is found high in the west after sunset. Jupiter and Saturn can be found in the east southeast before sunrise.

Mars

Currently Mars appears as a 1.1-magnitude object that will be visible high in the west about 40 minutes after sunset. Mars sets by 12:07 a.m.

Jupiter

Jupiter is starting to climb out of the Sun’s glare just before sunrise. For your best chance to see Jupiter, look east southeast 40 minutes before sunrise.

Saturn

Saturn has returned to our morning sky. Look east southeast 1 hour before sunrise to find the ringed planet.

Mars Perseverance Rover Update

After a successful landing on Mars, NASA’s newest rover Perseverance continues to go through testing before it starts its mission. Each week this section will contain a few of the images sent back to Earth as Perseverance explores Jezero crater. If you have not seen it yet, the first thing I would recommend watching is a video NASA released last week of the rover’s landing. Additionally, the rover has released a few panoramic views from its landing site that you will be better off going to NASA’s website to see. The video and panoramic images can be found at here.

NASA’s Mars Exploration Program website will be a good resource to visit each day to find any updates on the rover and its mission. Aside from information about Perseverance, NASA’s website will keep you up to date on any new findings from other Mars missions and research.

A Rock Named Maaz is the First Target of Scientific Interest for Perseverance
Credit: NASA/JPL-Caltech

SuperCam Close-Up of ‘Yeehgo’ (‘Yéigo’) Target
Credit: NASA/JPL-Caltech/LANL/CNES/CNRS/ASU/MSSS

James S. McDonnell Planetarium

Night Sky Update: March 12-March 20, 2021