September 6, 2021: Mercury, Venus, Jupiter, and Saturn shine in the evening sky. The moon is at its New moon phase at 7:52 p.m. CDT.
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by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 6:22 a.m. CDT; Sunset, 7:15 p.m. CDT. Check local sources for sunrise and sunset times for your location.
Step outside at least an hour before sunrise. The eastern sky is full of stars – Sirius, Betelgeuse, Procyon, Rigel, Capella, and Aldebaran. The moon has completed its tour of the morning star clusters. It reaches its new phase this evening. Look for a very thin moon tomorrow evening shortly after sunset in the western sky. On September 9, the moon and Venus appear together.
Mercury is over a week away from its evening greatest elongation. The plane of the solar system is poorly inclined to the western horizon in the northern hemisphere at this time of the year. Venus and Mercury seemingly struggle to higher altitudes in the western sky.
Our southern hemisphere readers can attest that Venus and Mercury are high in the sky after sunset. At one hour after sundown, Mercury is 12° up in the west, while Venus is nearly 30° up in the western sky.
From mid-northern latitudes, Mercury is 5° up in the west-southwest at twenty-five minutes after sunset. This speedy planet is about 5° up in the west-southwest. Brilliant Venus is 15.2° to the upper left of Mercury.
Mercury is moderately bright, but at this level of twilight, a binocular is needed to see it.
As the sky darkens further, Venus is one evening past its conjunction with Spica. The planet is 2.0° to the upper left of the star. With a binocular notice that Venus is 0.1° to the lower left of 76 Virginis (76 Vir on the chart).
Farther eastward, Jupiter and Saturn are in the southeastern sky. After Venus sets 90 minutes after sunset, Jupiter is the brightest “star” in the sky. Saturn, besides Jupiter only Arcturus and Vega are brighter, is over 17° to the upper right of Jupiter.
Both planets are retrograding in front of the stars of Capricornus. This westward motion is an illusion from our planet’s faster trip around the sun. Because they revolve around the sun slowly, they change their places slowly from night to night. In comparison, Venus moves very quickly. Note the brilliant planet’s location with 76 Virginis tonight compared to its location tomorrow evening.
Two hours after sunset, find them higher in the sky toward the south-southeast. Use a binocular to see the distant stars. Jupiter is 1.3° to the lower right of Mu Capricorni (μ Cap on the chart) and 1.7° to the upper left of Deneb Algedi – “the kid’s tail.” Saturn is 1.0° below Upsilon Capricorni (υ Cap).
As midnight approaches, Jupiter and Saturn are in the southern sky. They set in the southwest well before sunrise.
Detailed Daily Note:The New moon phase occurs at 7:52 p.m. CDT. Twenty-five minutes after sunset, use a binocular to find Mercury about 5° up in the west-southwest. Twenty minutes later, Venus is about 8° up in the west-southwest, 2.0° to the upper left of Spica. Venus continues to step eastward compared to the starry background as it opens a gap with Spica. Use a binocular to spot the brilliant planet 0.1° to the lower left of 76 Virginis (76 Vir, m = 5.2). At this hour, Saturn is over 20° above the southeast horizon. Bright Jupiter, 17.1° to the lower left of the Ringed Wonder, is about 15° up in the southeast. Both planets continue to retrograde in Capricornus. Jupiter is moving faster and cutting the gap. It does not back up far enough to get close to Saturn. Two hours after sunset, Jupiter – 25.0° above the southeast horizon – is 4.1° to the upper right of ι Aqr, 1.3° to the lower right of μ Cap, and 1.7° to the upper left of Deneb Algedi. Saturn, to the upper right of Jupiter, is nearly 27° up in the south-southeast, 1.0° below υ Cap.
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