August 26, 2023: Saturn is at opposition overnight. The moon appears to be boiling in the Teapot of Sagittarius. Venus, Jupiter, and Saturn are visible simultaneously before sunrise.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 6:10 a.m. CDT; Sunset, 7:34 p.m. CDT. Check local sources for sunrise and sunset times. Times are calculated by the US Naval Observatory’s MICA computer program.
Here is today’s planet forecast:
Morning Sky
An hour before sunup, Venus, Jupiter, and Saturn are along an imaginary arc stretching from the east to the west-southwest. Brilliant Venus resumes its reign as the Morning Star. Find it less than 5° up in the east. It rises nearly 80 minutes before the sun and gains seven minutes of rising time each morning.
At this hour look for Sirius, nearly 10° above the east-southeast horizon and over 40° to the upper right of Venus. Beginning about September 10 and running throughout the month, Venus and Sirius are about the same altitude – height above the horizon – during morning twilight. While Venus does not closely pass Sirius, the brightest planet and the brightest star stand in the eastern sky before sunup.
The second planet, Jupiter, is high in the south-southeast, brighter than Sirius, but fainter than Venus. It is slowly moving eastward in front of Aries, 13.5° to the lower left of Hamal, the constellation’s brightest star, and nearly 16° to the lower right of the Pleiades star cluster that is part of Taurus.
Jupiter begins the illusion of retrograde early next month. This is from Earth overtaking the slower Jovian Giant. The line of sight that normally shows Jupiter moving eastward begins to move westward. Jupiter does not change direction in its orbit, but our faster-moving planet creates this illusion.
Through a telescope with a magnification of 80x, Jupiter and its four brightest moons – Io, Europa, Ganymede, and Callisto – are visible, along with the star Sigma Arietis (σ Ari on the chart) that has been imitating a new bright Jovian moon. Europa, Ganymede, and Callisto are to the west of the planet and Sigma is beyond them, nearly in their plane. The star serves as a distant fixed point to see the planet gently move eastward and pass it, making this illusion that the star is a new moon of the planet.
Look carefully for Io, immediately east of Jupiter. Another higher magnification eyepiece might be necessary to see it. With the higher power, Io’s shadow is cast on the cloud tops. Find the Great Red Spot turning earthward, reaching the center of the planet at 7:26 a.m. CDT, long after sunrise in Chicago. Western North American time zones see the Red Spot in a darker sky.
The third bright planet is Saturn, over 10° above the west-southwest horizon. Less than 24 hours before opposition, when Earth is between the planet and the sun, the Ringed Wonder is retrograding in front of Aquarius, 8.3° to the lower right of Skat, the Aquarian’s leg, and 8.1° to the lower right of Lambda Aquarii (λ Aqr on the chart). Together they nearly make an equilateral triangle.
Evening Sky
While east of the sun and in the evening sky, Mercury and Mars are awash in bright evening twilight. Mercury is quickly overtaking our planet, passing between the sun and us on September 6th, then skipping into the morning sky for its best morning appearance of the year. This evening, it sets less than twenty minutes after the sun.
Mars, much dimmer than might be expected, sets sixty minutes after sundown. It passes behind the sun during November and back into the morning sky during early 2024. On its return to the morning sky, Mercury passes it on January 27th, followed by a Venus-Mars conjunction on February 22nd.
Today’s news, though, is Saturn’s opposition that occurs overnight, 3:28 a.m. CDT. At opposition, the sun and planet are in opposite directions from Earth, 180° apart, that is. In our sky, when the sun rises in the east, Saturn sets in the west. After midnight (with daylight time adding in an extra hour), Saturn is south. So, this evening as the sun sets in the western sky, Saturn rises farther eastward. An hour later, Saturn is nearly 10° up in the east.
Through a telescope later this evening, when it is higher, the rings are easy to discern. If you have been watching Jupiter through a telescope in the morning, Saturn with its rings appears about the same diameter as the Jovian Giant. The rings are inclined nearly 9° and not as open as at other oppositions.
While tonight is the opposition date, the planet is higher in the sky each evening and easier to view through a telescope earlier during the night. Look for public viewing nights, sponsored by local museums or astronomy clubs, to see Saturn through a telescope during the next several weeks. Or convince the neighborhood sky watcher to provide a look at Saturn through their telescope. Seeing this planet through a telescopic eyepiece is a memorable experience.
This evening Titan, the planet’s largest moon, is east of the rings. It is the second largest moon in the solar system, after Jupiter’s Ganymede, and the only one known with an appreciable atmosphere. The surface atmospheric pressure is about 50% stronger than Earth’s.
In addition to Titan, up to five other Saturnian moons are visible, including Dione, Tethys, Rhea, and Iapetus. Enceladus appears below the rings against the southern hemisphere. Look for it through a higher magnification eyepiece.
Tonight, Earth’s moon, 78% illuminated and about 20° up in the south, seems to be boiling in the Teapot of Sagittarius. With the bright moonlight, the starry background is challenging to see. Use a binocular to trace the pot’s shape and notice the moon’s location near the middle.
Jupiter follows Saturn across the horizon about three hours after sundown. Around midnight, it is 10° up in the east.
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