2021, December 4:  Moon Cues Mars


December 4, 2021:  Before sunup the thin crescent moon guides us to dim Mars.  In the evening sky, Evening Star Venus, Saturn and Saturn shine from the southern sky.

Chart Caption – 2021, December 2: A binocular view of the waning crescent moon, Zubenelgenubi, and Mars.


by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 7:02 a.m. CST; Sunset, 4:20 p.m. CST.  Check local sources for sunrise and sunset times for your location.

Mars is climbing into the morning sky after its solar conjunction about two months ago.  The planet is now unexpectantly dim.  It is over 230 million miles away.  Additionally, the planet is small and it only reflects about 20% of the sunlight that strikes its surface.  Mars is bright when close to Earth.  This occurs about every two years when Earth moves between Mars and sun.  Otherwise, Mars presents itself as a somewhat bright star that moves eastward compared to the starry background.

This morning the thin crescent moon, 5% illuminated, is to the upper right of Mars.  Here’s how to look for the Red Planet.  At 45 minutes before sunup, find the thin lunar slice, about 13° up in the southeast.  With a binocular place the moon in the upper right edge of the field of view.  Mars is 6.6° to the lower left of the moon, near the edge of the binocular field.

Evening Sky

The three evening planets, Venus, Saturn and Jupiter, are in the southern sky after sunset.  Exceedingly brilliant Venus is low in the south-southwest, easily mistaken for lights on an airplane.

Bright Jupiter is about one-third of the way up in the south.  Saturn, dimmer than the other two planets, is between Jupiter and Venus.

In two evenings, Venus and the thin crescent moon appear together after sundown.



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