July 17, 2023: Five planets – Mercury, Venus, Mars, Jupiter, and Saturn – are visible during nighttime hours. The Scorpion crawls across the southern horizon during the evening.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 5:30 a.m. CDT; Sunset, 8:23 p.m. CDT. Check local sources for sunrise and sunset times for your location. Times are calculated by the U.S. Naval Observatory’s MICA computer program.
Summaries of Current Sky Events
SUMMARY FOR VENUS AS AN EVENING STAR
Here is today’s planet forecast:
Morning Sky
Jupiter and Saturn are the morning planets. Rising over five hours before sunrise, Jupiter is nearly 40° above the east-southeast horizon at one hour before sunrise. The planet is slowly moving eastward in front of Aries, 11.8° below Hamal, the constellation’s brightest star, and 11.7° above Menkar, Cetus’ nostril.
Through a telescope at 4:22 a.m. CDT, the planet’s Great Red Spot, a long-lived storm in the clouds is at the center of the planet in the southern hemisphere.
Saturn is in the south-southwest this morning. Rising before midnight, the planet appears here during morning twilight.
The Ringed Wonder is retrograding in front of Aquarius, 7.0° to the upper right of Skat, meaning “the leg,” and 5.6° to the lower right of Lambda Aquarii (λ Aqr on the chart).
Retrograde motion is an illusion when Earth overtakes an outer planet and passes between it and the sun. Earth and Saturn revolve in a counter clockwise direction from north of the solar system. As Earth moves between the sun and planet, the line of sight, that normally moves eastward compared to the stars, moves westward, giving the illusion that Saturn is backing up.
The moon is at its New moon phase at 1:32 p.m. CDT.
Evening Sky
A planet traffic jam occurs in the evening sky during brighter twilight. Brilliant Venus shines through evening twilight, but a binocular is needed to see Mercury, Mars, and the star Regulus.
Find a clear view toward the west. A hilltop or elevated structure provide views across possible obstructions. By forty-five minutes after sunset, brilliant Venus is less than 10° above the horizon.
Use the optical assist to find Regulus in the same binocular field with Venus, 3.5° above the Evening Star. Then find Mars, 4.5° to the upper left of Regulus. Depending on the binocular’s characteristics, the grouping may snugly fit into the same field of view.
Setting an hour after the sun, Mercury is very low in the west-northwest, over 15° to the lower right of Venus. At this altitude – height above the horizon – the atmosphere dims and reddens celestial objects. A binocular is needed.
As twilight ends at this season, the Scorpion crawls across the southern horizon. The brightest star, Antares, meaning “the rival of Mars,” is over 20° above the south-southwest horizon. It is one of the largest known stars in our region of the Milky Way galaxy. Given its reddish hue and its incredible intrinsic brightness, the star is about 250 times the sun’s diameter.
From Antares, the body of Scorpius can be traced downward toward the horizon and then curves back up ending at Shaula – meaning “the cocked-up part of the tail” – and Lesath – “the sting.” The stars appear close together and are sometimes named “the Cat’s Eyes.”
Moving westward from Antares, the forehead is marked by Dschubba. The claws, today part of Libra, reach westward. The stars retain their historic names Zubeneschamali – the northern claw – and Zubenelgenubi – the southern claw.
Explore this region of the sky with a binocular. The direction of the galaxy’s center is to the upper left of Shaula and Lesath behind Sagittarius, the next constellation eastward. Star clusters, star clouds, lanes of dust, and gaseous nebula are visible in this area.
Messier 4 (M 4 on the chart) is easily located in the same binocular field with Antares. It is a globular cluster appearing as a tiny cotton ball-like stellar bundle. It has thousands of stars. These clusters revolve around the galaxy outside the plane and a map helped astronomers predict the direction of the galactic center. Other star clusters, like the Pleiades, Hyades, and Beehive mark the plane of the galaxy and revolve around the center along that plane.
Check out this region of the sky before the moon grows too bright and moves through this region.
Saturn rises about two hours after sunset and it is about 10° above the horizon an hour later.
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