September 23, 2023: The autumnal equinox occurs after midnight this morning. Uranus is visible through a binocular between Jupiter and the Pleiades star cluster.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 6:39 a.m. CDT; Sunset, 6:47 p.m. CDT. Check local sources for sunrise and sunset times. Times are calculated by the US Naval Observatory’s MICA computer program.
Astronomical autumn begins at 1:50 a.m. CDT. At this moment, the sun is above Earth’s equator. Until northern hemisphere’s spring equinox (March 19th, 10:06 p.m. CDT), the sun shines more directly on the southern hemisphere.
Because of the definition of sunrise and sunset and the bending of light when the sun is near the horizon, daylight and nighttime are not equal today. September 25th and 26th are the days when the twenty-four-hour day is almost – within a minute – equally divided between sunlight and nighttime.
Summaries of Current Sky Events
Summary for Venus as a Morning Star, 2023-24
Here is today’s planet forecast:
Morning Sky
Venus and Mercury shine brightly from the eastern sky before sunrise. Brilliant Venus is “that bright star” in the eastern sky during morning twilight. It rises nearly three and one-half hours before the sun. At that early hour, Saturn is about 10° up in the west-southwest.
Venus and Saturn are 180° apart in the sky on October 10th when Saturn sets as Venus rises. Saturn is challenging to see when it is near the horizon because it is not as bright as Venus or Jupiter and the blurring and dimming effects of the air make it fade from view several mornings before the opposition date. What is the last date that you see them in the sky at the same time?
An hour before daybreak, Venus stands over 25° up in the east and 12.5° to the upper right of Regulus, Leo’s brightest star. The planet is stepping toward the star, passing by on October 9th.
At this hour Mercury is 5° above the horizon and 12.2° to the lower left of Regulus. The planet is noticeably brighter than Regulus. Yesterday, Mercury was at its largest separation from the sun, known as the greatest elongation. As it recedes into brighter twilight, it brightens and loses fourteen minutes of rising time compared to sunrise during the next week.
As twilight brightens, Mercury is higher in the sky, eventually disappearing into the brighter light near sunrise.
During earlier twilight, Venus and Sirius, night’s brightest star, are nearly the same altitude – height above the horizon. The Dog Star is in the south-southeastern sky about 40° from Venus. Because of the Dog Star’s large distance from the ecliptic – the plane of the solar system where the planets move – there is no close Venus-Sirius conjunction. We can admire the brightest planet and the brightest star in the same general direction and altitude in the morning sky.
Procyon, the Little Dog Star, is above an imaginary line from Venus to Sirius. From the mid-northern latitudes, Procyon rises about 30 minutes before Sirius, and its name means “before the dog.”
An hour before daybreak, Jupiter is high in the southwest, retrograding in front of Aries, 13.3° to the left of Hamal, the Ram’s brightest star, and 11.2° to the upper right of Menkar, Cetus’ nostril, and 16.3° to the lower right of the Pleiades star cluster.
During the next several mornings, watch the Jovian Giant cross an imaginary line from Hamal to Menkar.
With a binocular look for planet Uranus. It is between the Pleiades star cluster and Jupiter, but neither celestial landmark is in the field of view with Uranus. It is in a fainter starfield with stars named with Greek letters or numbers, such as 63 Arietis (63 Ari on the chart), Tau Arietis (τ Ari), Zeta Arietis (ζ Ari), and Delta Arietis (δ Ari). The field is distinctive and when the stars are located, place them to the upper right edge of the view. Uranus, distinctly dimmer than the reference stars, is near the center of the field. The planet is easier to see before twilight begins. With a binocular, the planet is visible from suburban and some urban settings, where the view is affected by the constant glow of outdoor lighting.
Evening Sky
Dim Mars continues its slide into bright twilight. Setting about forty minutes after sunset, it passes solar conjunction during November.
The waxing gibbous moon, 64% illuminated, is about 20° up in the south, near the Teapot’s handle, a modern nickname for Sagittarius. It is 1.6° to the lower left of Tau Sagittarii (τ Sgr on the chart). With the bright moonlight, use a binocular to see the Teapot and the moon near the star.
From South America, the moon occults or eclipses the star this evening.
Saturn is farther eastward from the moon, about 20° above the southeast horizon. The planet rises before sunset and appears higher in the sky each evening as night falls.
The Ringed Wonder is retrograding in front of Aquarius, 9.7° to the upper right of Skat, the Aquarian’s leg, and 10.1° to the right of Lambda Aquarii (λ Aqr on the chart). With this moonlight, use a binocular to see the stars.
During the night, Saturn is in the south before midnight. About three hours before sunrise, try to see it at the same time Venus appears in the eastern sky.
Bright Jupiter rises less than two hours after sundown and is in the eastern sky near midnight. By tomorrow morning the planet is high in the southwest.
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