September 1, 2023: The gibbous moon is visible during the night. Venus, Jupiter, and Saturn are visible along an imaginary arc from east to the west-southwest.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 6:16 a.m. CDT; Sunset, 7:24 p.m. CDT. Check local sources for sunrise and sunset times. Times are calculated by the US Naval Observatory’s MICA computer program.
The month opens with daylight lasting thirteen hours, eight minutes. During September, daylight decreases by 80 minutes.
The equinox occurs September 23rd at 1:50 a.m. CDT, signaling the beginning of autumn in the northern hemisphere, although meteorologists use today as the beginning of the autumn season (September through November).
The five-planet morning parade continues with Venus, Jupiter, and Saturn easily visible. Uranus is easy to locate through a binocular between Jupiter and the Pleiades star cluster. The challenging view, even through a binocular, is locating Neptune in a dim Pisces starfield, over 20° to the upper left of Saturn. For sky watchers interested in seeing the two more distant planets, see the directions in the August 27th article.
Saturn leads the planet parade beginning at sunset, appearing in the east-southeast. Jupiter follows later, with Neptune between them. Uranus rises after Jupiter and then Venus appears before sunrise. The three bright planets are along an arc from the east to the west-southwest with Uranus and Neptune spaced between them.
Summaries of Current Sky Events
Here is today’s planet forecast:
Morning Sky
One hour before sunrise, the bright moon, 97% illuminated, is about one-third of the way from the southwest horizon to overhead. Its light washes out the dimmer stars and brightens the terrestrial landscape.
Saturn, becoming more difficult to see at this time interval before daybreak, is about 6° above the west-southwest horizon and nearly 24° to the lower right of the lunar orb.
The planet is retrograding in front of Aquarius, but the background stars are difficult to see in this moonlight and the Ringed Wonder’s low altitude – height above the horizon.
At this hour, Jupiter is high in the southern sky and west of the south cardinal point. The Jovian Giant is slowly moving eastward in Aries, 13.6° to the lower left of Hamal, the constellation’s brightest star, and nearly 16° to the lower right of the Pleiades star cluster, part of Taurus.
Jupiter is slowing before it appears to begin the illusion of retrograde motion, westward movement compared to the starry background on the 4th.
The moon is about one-third of the way from Saturn to Jupiter.
This moonlight washes over the dimmer stars. Use a binocular to see the Pleiades star cluster.
Farther eastward, Brilliant Venus is nearly 10° up in the east. It continues to rise six to seven minutes earlier compared to sunrise each morning. Look for Procyon and Sirius, the night’s brightest star. Beginning about the 10th and running through the end of the month, Venus and Sirius are about the same altitude during morning twilight. By month’s end the Morning Star rises three hours, thirty-six minutes before the sun, standing high in the eastern sky during morning twilight.
Evening Sky
Mercury and Mars are hiding in bright sunlight. Mercury is at inferior conjunction – between Earth and Sun – on the 6th. It then moves into the eastern sky before sunrise, making its best morning appearance of the year.
Mars is much dimmer than we might expect. It sets and hour after sunset. The planet slowly slips into bright twilight, losing one to two minutes of setting time compared to sunset each night. By month’s end it sets thirty-eight minutes after the sun. Solar conjunction occurs on November 18th, followed by a slow climb into the morning sky. A conjunction with Mercury occurs January 27th, 2024, followed by a Venus conjunction February 22nd.
Saturn is rising before sunset. Two hours after sundown, it is over 20° above the southeast horizon. The moon, 94% illuminated, is less than 10° up in the east and over 35° to the lower left of Saturn.
Jupiter rises less than three hours after sundown. As midnight approaches, the Jovian Giant is in the eastern sky.
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