July 29, 2022: Jupiter’s retrograde begins today. The Southern Delta Aquariid meteor shower peaks after midnight. Four morning planets parade across the sky. Catch a glimpse of Mercury after sunset.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 5:42 a.m. CDT; Sunset, 8:12 p.m. CDT. Check local sources for sunrise and sunset times for your location.
Daylight is back to 14 hours, 30 minutes. The sun is in the sky about 45 fewer minutes today than it was at the first day of summer.
The Southern Delta Aquariid meteor shower peaks after midnight and before morning twilight begins. With the moon at a thin waxing phase and Jupiter and Saturn to generally guide you to the shower’s radiant, this shower may show a dozen bright meteors each hour. It’s not a high rate, but with a clear summer night, the Milky Way, and bright planets, this is worth the night under the starry sky. Look between Jupiter and Saturn and above the star Fomalhaut.
The annual Perseid meteor shower occurs next month when the moon is bright. Because of the moon’s light, the Southern Delta Aquariid shower may be the best this summer.
Sirius is at its heliacal rising today at latitude 25°. The first appearance of the night’s brightest star varies by latitude. More southerly latitudes see it earlier during the summer. The first appearance at latitude 40° north is August 10.
Jupiter stops moving eastward today and slowly begins the illusion of retrograde motion. This effect occurs when Earth begins to move between the distant planet and the sun.
Mars, Jupiter, Saturn and the other dimmer objects farther from the sun move more slowly in their solar treks. As our faster-moving planet moves inside them, they seem to stop moving eastward and begin this westward illusion. This occurs when the line of sight from Earth to the planet starts to shift westward.
As Earth passes between the planet and the sun, the planet is at its fastest westward apparent speed and the planet begins to slow. After a time, the planet seems to stop retrograding, returning to its normal eastward course.
Earth passes between Jupiter and the sun on September 26. The planet resumes its eastward direction again on November 24.
On the chart above, Earth and Jupiter are shown, if they could be viewed from north of Earth’s northern hemisphere. The three dates are shown from Earth’s position. Jupiter’s corresponding position is shown as well. Three lines connect the two planets and extend toward the distant starfield. Along with the dates, the lines are marked with letters. The two planets are moving eastward along their imaginary orbital paths. Note that as Earth passes between the sun and Jupiter, that from the letters A to C, the line of sight from Earth to Jupiter, backs up or moves westward – retrograde motion.
Here is the planetary forecast for today:
Jupiter is over halfway up in the south during morning twilight, about an hour before sunrise. As noted previously, the planet starts its retrograde today in front of the stars of Cetus, the Sea Monster. The creature’s tail, Deneb Kaitos, is below the Jovian Giant and lower in the sky.
Jupiter’s retrograde is slow at first and gently picks up westward speed, moving back into Pisces on September.
Looking at Jupiter with a binocular or spotting scope, the large moon Callisto is at its maximum separation from the planet this morning. It appears as a star to the east (left) of the planet.
Saturn is over 20° above the southwest horizon and over 45° to the lower right of Jupiter. The Ringed Wonder is retrograding in eastern Capricornus near the stars Deneb Algedi and Nashira.
The star Fomalhaut, meaning “the mouth of the southern fish,” is less than 20° up in the south-southwest. The radiant of this morning’s meteor shower is above this star and between Jupiter and Saturn.
Through a binocular, Saturn is making an isosceles triangle with the two stars. Look again tomorrow morning when the shape takes place.
Shift the binocular field slightly so the star Iota Capricorni (ι Cap on the chart) comes into view with the trio. Saturn is retrograding toward that star. During the next several weeks, watch it move away from Deneb Algedi and Nashira.
Farther eastward brilliant Venus and Mars are joined by several bright stars. Venus continues to appear low in the east-northeast during morning twilight. It is on a very slow slide toward the sun that ends with its superior conjunction during early October. This morning, it rises 111 minutes before sunrise. Each morning it rises one to two minutes later until its solar conjunction.
At one hour before sunrise the Morning Star is less than 8° up in the east-northeast. Find an observing spot with a clear horizon in that direction.
Castor and Pollux, the Gemini Twins, are about 12° to the left of the planet. Use a binocular to see them, especially Pollux. It is making its first morning appearance.
To the right of Venus, Orion is stepping across the horizon in the east. His shoulders, Betelgeuse and Bellatrix, are easier to spot. Betelgeuse is slightly higher than Venus while Bellatrix is over 5° higher. Use a binocular to find the belt stars and Rigel, Orion’s knee.
Taurus is higher in the sky, above Orion. The Bull’s head is marked by a sideways letter “V,” formed by the star Aldebaran and the Hyades star cluster. The horns, Elnath and Zeta Tauri (ζ Tau on the chart) are to the lower left of the head. This bull has considerably long horns! The Pleiades star cluster rides on the Bull’s back.
Mars is over halfway up in the sky in the east-southeast. Growing in brightness, but not nearly as bright as Venus or Jupiter, the Red Planet is 15.0° to the upper right of the Pleiades. Mars eastward march carries it into Taurus and past the star cluster on August 20. There is a spectacular bunching of Mars, Moon, and Pleiades on August 20. All fit into a binocular field of view on the 19th.
Mars reaches its opposition on December 7 to the upper left of Aldebaran. During the next several months, watch the Red Planet move through Taurus. The four morning planets span over 140° from Venus t to Saturn.
For those looking for an observing challenge, the thin crescent moon and Mercury are visible about 30 minutes after sunset, very low in the west-northwest. The crescent moon, 2% illuminated, is about 4° up in the sky. Mercury is 2.6° to the lower left of the crescent. Both easily fit into the same binocular field of view. The speedy planet sets only 16 minutes later. The planet is reasonably bright, but immersed in bright twilight. With the binocular scan across the horizon to find that razor-thin moon and then look for Mercury to the lower left. Or perhaps Mercury is spotted first. Then find the moon.
This observation generally describes Mercury’s appearance during this apparition. Each evening the planet is slightly dimmer and slightly higher in the sky during brighter twilight, setting less than an hour after sunset near mid-August.
Saturn rises less than an hour after sunset, leading the planet parade that peaks before sunrise. Two hours later, the Ringed Wonder is low in the southeast, while Jupiter is above the horizon in the east. Mars follows Jupiter across the horizon about 90 minutes after the Jovian Giant Rises. By an hour before sunrise, the four bright planets are strung from the east-northeast horizon to the southwest.
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