2021, September 19: Three Evening Planets, Bright Moon

September 19, 2021:  Three bright planets – Venus, Jupiter, and Saturn – are easily visible after sunset, along with the nearly-full moon.

2021, September 19: Venus shines brightly from the west-southwest. It is 5.2° to the lower right of Zubenelgenubi and nearly 30° to the lower right of Antares.
Chart Caption – 2021, September 19: Venus shines brightly from the west-southwest. It is 5.2° to the lower right of Zubenelgenubi and nearly 30° to the lower right of Antares.

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by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 6:35 a.m. CDT; Sunset, 6:53 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

As the Harvest Moon and Autumnal Equinox approach, three bright planets are visible in the evening sky.

Bright Venus is low in the west-southwest after sunset.  On the chart above, about 45 minutes after sunset, the brilliant planet is about 8° up in the west-southwest.  Find a clear horizon, away from trees, houses, and other obstructions.  Initially, use a binocular to spot Zubenelgenubi, “the southern claw,” 5.2° to the upper left of the planet.  Additionally, Antares is about 30° to the upper left of Venus.

Venus is rapidly moving eastward compared to the starry background. It is moving over 1° each day.  Nightly changes are easy to see.  Venus passes Antares in about a month.

2021, September 19: The nearly-full moon, bright Jupiter and Saturn are lined up in the southeast after sunset.
Chart Caption – 2021, September 19: The nearly-full moon, bright Jupiter and Saturn are lined up in the southeast after sunset.

Farther eastward, the bright moon, one day before its full (Harvest) moon phase, the lunar orb is low in the east-southeast.  Bright Jupiter is over 20° to the upper right of the moon.  Saturn is 16.3° to the upper right of Jupiter.

Jupiter and Saturn are retrograding in front of the dimmer stars of Capricornus.  This illusion is an effect from our faster moving planet passing and moving away from these two giant worlds. Their nightly movement is difficult to observe compared to Venus.  They continue at their pokey westward speeds until next month when they seem to reverse their directions and head eastward again compared to the sidereal backdrop.

Venus sets 94 minutes after sunset. Jupiter and Saturn are in the southern sky before midnight. The moon is in the sky nearly all night.

Detailed Daily Note: Brilliant Venus (m = −4.2) is over 8° up in the west-southwest about 45 minutes after sunset.  Moving eastward in Libra, Venus is 5.2° to the lower right of Zubenelgenubi. Note that the planet is nearly 30° to the lower right of Antares (α Sco, m = 1.0), over 15° up in the west-southwest.  Farther eastward, less than 24 hours before the Full moon phase, the lunar orb (13.0d, 99%) is 8.0° up in the east-southeast. Jupiter, over 19° up in the southeast, is nearly 23° to the upper right of the moon.  Saturn, over 23° above the south-southeast horizon, is 16.3° to the upper right of the Jovian Giant.  Two hours after sunset, the moon is 20.0° up in the southeast.  Jupiter is to the upper right of the moon.  Use a binocular to see the dimmer stars in the same field of view as Jupiter.  The planet is 2.5° to the right of μ Cap, 1.4° to the upper right of Deneb Algedi, and 2.0° to the upper left of Nashira.  Saturn, over 28° above the south-southeast horizon, is 1.2° to the lower right of υ Cap.  Both planets continue to retrograde.

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