2021, July 17: Line Dance in Evening Western Sky

July 17, 2021: Evening Star Venus and Mars continue their seemingly choregraphed line dance in the western sky after sunset.  Venus is east of Mars and moving toward the star Regulus.

2021, July 17: Forty-five minutes after sunset, brilliant Venus is low in the western sky, 2.6° to the upper left of Mars and 4.9° to the lower right of Regulus.
Chart Caption – 2021, July 17: Forty-five minutes after sunset, brilliant Venus is low in the western sky, 2.6° to the upper left of Mars and 4.9° to the lower right of Regulus.

by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 5:31 a.m. CDT; Sunset, 8:23 p.m. CDT.  Check local sources for sunrise and sunset times for your location.

Brilliant Venus shines in the western sky after sundown, poking through the many colors of evening twilight.  Five days after its conjunction with Mars, the Evening Star is 2.6° to the upper left of the Red Planet and 4.9° to the lower right of Regulus.

Forty-five minutes after sunset, look for Venus about 8° up in the west-northwest.  From its low altitude in the sky, find a spot with a clear horizon in that direction, such as a hilltop or an elevated structure.

Use a binocular to find Mars and Regulus.  The trio does not fit into the same field this evening.  It’s either Venus and Mars or Venus and Regulus in the same field of view.

Regulus appears lower in the sky each evening as it soon disappears into the sun’s bright light.    It is the closest bright star to the ecliptic.  It is in conjunction with the sun on August 22.

As Earth continues to move away from Mars, the planet dims and appears closer to the sun.  Its solar conjunction is on October 7.  The planet is on a slow slide into bright twilight.

Venus continues its slow climb into the western sky.  It appears there until early 2022.

2021, July 17: An hour after sunset, the slightly gibbous moon appears above a line from Spica to Zubenelgenubi, about 11° from each star.
Chart Caption – 2021, July 17: An hour after sunset, the slightly gibbous moon appears above a line from Spica to Zubenelgenubi, about 11° from each star.

The slightly gibbous moon is over one-third of the way up in the sky in the southwest, above an imaginary line from Spica to Zubenelgenubi.  The lunar orb is about 11° from each star.

As the evening progresses, Venus, Mars, and Regulus appear lower in the sky.  About 80 minutes after sunset, brilliant Venus is very low in the west-northwest and Saturn is about 5° up in the east-southeast.

Venus sets over 90 minutes after sunset and Jupiter rises 11 minutes later.  The Venus – Jupiter opposition occurs in a few evenings.  By late in the month, Venus is visible in the western sky while Jupiter and Saturn are in the southeast.

Additionally, Saturn is approaching its opposition with the sun on August 2, when it rises at sunset, appears in the southern sky near midnight, and sets in the west-southwest as the sun rises.  The sun and Saturn are in opposite directions in the sky.

Continue to watch the evening line dance in the western sky after sunset. Tomorrow evening Venus, Mars, and Regulus tightly fit into the same binocular field of view.

Detailed Daily Note: One hour before sunrise, Saturn is nearly 22° above the southwestern horizon.  It is retrograding in Capricornus, 2.8° to the lower right of θ Cap. Bright Jupiter (m = −2.8), over 34° up in the south-southwest, is 19.7° to the upper left of Saturn.  It is retrograding in Aquarius, 2.2° to the upper left of ι Aqr, 4.5° below θ Aqr, and 4.6° to the lower right of σ Aqr. The Jovian Giant is visible to the lower right of a line from 38 Aqr to 42 Aqr. Forty-five minutes before sunrise, Mercury (m = −0.9) is over 4° up in the east-northeast. The moon is at its First Quarter phase at 5:11 a.m. CDT.  Pluto (m = 14.3) is at opposition at 5:46 p.m. CDT. One hour after sunset, the moon (8.0d, 58%) is over 30° up in the southwest, above a line from Spica to Zubenelgenubi (α Lib, m = 2.8).  The lunar orb is 11.1° to the upper left of Spica and 11.0° to the right of Zubenelgenubi.  Farther west, brilliant Venus is nearly 6° up in the west-northwest, 2.6° to the upper left of Mars and 4.9° to the lower right of Regulus. Saturn, slowly approaching its opposition with the sun, rises 48 minutes after sunset.  Venus sets 45 minutes later.  Jupiter rises 11 minutes after Venus sets.  The Venus – Jupiter opposition occurs in a few evenings.  As midnight approaches the moon is 10.0° up in the west-southwest.  Farther eastward, Saturn is over 22° above the southeast horizon.  Jupiter is to the Ring Wonder’s lower left, nearly 17° above the horizon.

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