September 17, 2022: Saturn leads the planets westward during the night. It is followed by Jupiter, Mars, and the moon that is nearly between the Bull’s horns.
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by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 6:33 a.m. CDT; Sunset, 6:57 p.m. CDT. Check local sources for sunrise and sunset times for your location.
A parade of three bright planets – Mars, Jupiter, and Saturn – makes its way westward during the night, readying for a bright five-planet display at year’s end.
The giant planets Jupiter and Saturn seem to follow the seasonal westward progression of the constellations from Earth’s revolution around the sun. Their eastward treks are slow, Jupiter takes nearly 12 years to revolve around the sky and to make a 360°-circuit against the distant stars. Saturn takes nearly 30 years to complete the same. Each night their motion against the distant starfields is small, but easy to watch as well as the melodic revolutions of their moons. These planets generally stay within a small region of the sky for an entire Earth year.
Because of their slow orbital motions, they generally follow the annual westward journeys of the stars. As Earth revolves around the sun, the stars first appear in the east before sunrise. Several weeks later they are in the south before daybreak, followed by a westward starting point. The stars become easy to spot in the evening sky in the east after sunset, then in the south weeks later. This is followed by them starting in the western sky after sunset and then disappearing into bright evening twilight, only to reappear sometime later in the east before sunrise to repeat the pattern.
Mars, on the other hand revolves around the sun at about half Earth’s pace. Its eastward march against the stars is easy to track. It does not follow the annual westward pace that reflects Earth’s revolution. It takes about two Earth years to appear in the east before sunrise until it disappears in the western sky after sunset.
Mars is nearing its opposition during December, retrograding from late October to mid-January. During this period, it will trek westward with Taurus. When it finally leaves the constellation in late March, Taurus starts the evening in the western sky. Until it disappears into bright twilight around summer’s mid-point, Mars seems to be scrambling eastward against the inevitable tide of evening twilight, but like gravity, it succumbs to Earth’s faster revolution, disappearing behind the sun. By then, Jupiter and Saturn are already back in the morning sky, following the westward ramble of the stars.
Earlier during the summer, five planets were visible simultaneously. Mercury seems to zigzag from morning sky to evening sky and back again at a seemingly dizzying pace. Depending on the solar system’s angle with the horizon, it can make a nice appearance against twilight or a ho-hum apparition that leaves it low in the sky and in bright twilight. In a week, it reaches its inferior conjunction between Earth and the sun, jumping into the eastern morning sky for its best morning appearance of the year. Then, after passing behind the sun, it joins Mars, Jupiter and Saturn during late December.
Venus seems to make a slow dance in the sky from evening to morning as it hugs the sun. Currently it is sliding back into bright morning twilight, after a spectacular display as the Morning Star. After its superior conjunction, it joins the other four bright planets in the evening sky for another five-planet display, this time, though, the order is mixed. Starting from the sun, it is Venus, Mercury, Saturn, Jupiter, and Mars.
Tonight, Saturn, Jupiter, Mars, and the moon, lie along the arc of the ecliptic – the plane of the solar system. The three planets are making that migration westward, appearing earlier in the sky each night. To catch them together and in places to see them earlier, this takes setting an early alarm, before Saturn is too low in the western sky. The chart above shows their places about five hours before sunrise (about 1:30 a.m. CDT in Chicago).
Start by looking for the slightly gibbous moon in the eastern sky. Mars is 4.7° to the right of the moon. Both easily fit into a binocular’s field of view.
Don’t confuse Mars with Aldebaran, the brightest star in Taurus, to Mars’ lower right.
At this hour, Jupiter is over halfway up in the south, while Saturn, dimmer than Jupiter and Mars, is only about 20° up in the southwest.
Tomorrow morning the configuration is nearly the same, but the moon is farther eastward, making a bigger gap back to Mars.
In about a month, the Red Planet appears above the eastern horizon about three hours after sunset, making this three-planet display visible at a more convenient time.
Morning Sky
SUMMARY OF PLANETS IN 2022 MORNING SKY
By an hour before sunrise, the moon is high in the south-southeast to the upper left of Mars. Notice that the lunar orb is nearly between the Bull’s horns – Elnath and Zeta Tauri – a precarious place to be.
At this hour Jupiter is low in the west-southwest. It is still the brightest star in the sky, until Venus rises 49 minutes before daybreak.
Fifteen minutes later, Morning Star Venus is low in the eastern sky. It is becoming a challenge to see because of its low altitude and obstructions blocking its view. The planet is quite bright even at this level of twilight, if there’s a clear sight line to the horizon.
Evening Sky
After sundown, bright Jupiter and Saturn are in the sky, leading the way westward. One hour after sunset, Jupiter is low in the east while Saturn is higher in the southeast. The Ringed Wonder is in the south before midnight.
Later Mars and then the moon appear above the eastern horizon, giving us the string of planets across the sky during the overnight hours.
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