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Astro Bob: See Saturn at its biggest and brightest of the year

On Aug. 14, Saturn and the Earth will be shy of a billion miles apart — as close as they get in 2022.

Saturn Hubble
The Hubble Space Telescope took this portrait of Saturn last September. It's currently late summer in the planet's northern (top) hemisphere with the rings tilted about 14° toward us. The bluish southern hemisphere, still steeped in winter, pokes out below the ring plane.
Contributed / Space Telescope Science Institute/NASA, ESA, A. Simon (NASA/GSFC)
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At a distance of 823.7 million miles (1.3 billion km) it might seem incredible we can see Saturn at all. Yet there it is, shining bright and true in the southeastern sky at nightfall. Even light, traveling at 186,000 miles a second, takes 80 minutes to get from there to here. That's why it feels slightly miraculous that a small refracting telescope magnifying 40x is all you need to reveal its signature rings.

Saturn in Capricornus
Saturn reaches opposition this year in far eastern Capricornus, a faint, triangle-shaped constellation in the southern sky. I took this photo on Aug. 13, 2022.
Contributed / Bob King

Every 378 days on average, Earth and Saturn line up together on the same side of the sun at opposition. This year, opposition occurs Sunday, Aug. 14, when the two planets will be at their closest for the year.

Saturn opposition
Saturn and the Earth line up together on the same side of the sun at opposition on Aug. 14, when the two planets will be closest for the year. Because the sun and Saturn lie on opposite sides of the Earth, we see Saturn rising in the east at the same time the sun sets in the west.
Contributed / Bob King

Earth is the faster planet, so it passes directly between Saturn and the sun on that day. From our perch, we look out and see Saturn directly opposite the sun in the sky, rising in the east about the same time the sun sets in the west.

Planets move slowly to the east (to the left if you face south) as they revolve around the sun. Each year, Saturn slides about 12° eastward through the zodiac constellations. That's the amount of sky covered by your fist held horizontally at arm's length. Even though Earth is the speedier planet, Saturn moves, too. We need extra time to catch up with the ring king, the reason oppositions occur about two weeks later each year.

Saturn finder
Use this map to help you find Saturn anytime this season. It's located in the southern sky well below the three stars that make up the Summer Triangle asterism. The map covers a large area, with Vega nearly overhead and Saturn a fist or two high in the southeastern sky. Together, the planet and three bright stars form the letter Y.
Contributed / Stellarium

Right now, the second largest planet shines from Capricornus the sea-goat. If you'd like to picture where Saturn will be in a year, measure off a fist to its lower left. That will bring you to Aquarius. Both constellations have no bright stars, one of the reasons Saturn stands out so well this season.

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Another is that its rings are tipped into view. Through a telescope they look as solid as a dinner plate. But the main rings are mostly composed of trillions of individual moonlets ranging from the width of your pinkie fingernail to the size of a guitar. They're made of 99.9% water ice, which is an excellent reflector of light.

Saturn orbit seasons King through 2032 S.jpg
During Saturn's 29-year orbit of the sun, we see different faces and aspects of the rings because of the planet's tilted axis. The north face is in view now and will be until the rings become edgewise at the planet's fall equinox in March 2025. Saturn's tilt means it has seasons just like the Earth does, but because it takes so long to orbit, each season lasts more than 7 years.
Contributed / Bob King

Similar to Earth, Saturn's axis is tipped 26.7°. During its 29-year orbit of the sun we first see the south face of the rings fully open and tipped toward us. Then the rings gradually close and become edgewise. In smaller telescopes they completely disappear from view and the planet appears noticeably fainter.

Soon after, the north face opens up and gradually reaches its maximum tilt about 7 years later. In August, Saturn's rings are tipped 14° (about halfway) and closing. They'll be edge-on again during the northern hemisphere fall equinox in March 2025.

A moment ago, I wrote that Saturn moves to the east as it circles the sun. That's true except around the time of opposition. As Earth laps the planet at that time, it appears to reverse direction and move west or "backwards." The same thing happens on the freeway when you pass a car in the left lane. As you zoom past, the car appears to move backwards from your perspective. Called retrograde motion, you can see it for yourself by comparing Saturn's changing position relative to nearby stars over the next few weeks.

Saturn moons
This is a simulated view of Saturn and its brighter moons through a telescope around 10:30 p.m. CDT Aug. 14. North is up and the left — the normal view. If you're looking through a reflecting telescope, flip the map upside down so south is up.
Contributed / Stellarium

Saturn comes into its own through a telescope. The rings look so much like the photos, first-time observers will sometimes kid that they must be fake. At low magnification a single ring shows. But if you increase the power to 125x or better, that ring divides into two: the outer A-ring, separated by a narrow, dark gap called Cassini's Division from the wide, bright B-ring. In 6-inch or larger instrument, a third, translucent C-ring glows subtly between the B-ring and Saturn's butterscotch globe.

Seeliger Effect
Can you see that Saturn's rings are brighter in the recent Aug. 11 photo compared to the one from May? This brightening is real and caused in part by the Seeliger Effect. For several days before and after opposition, the sun lies directly at our backs and illuminates the ring particles face-on. The shadows they cast are hidden behind their bulk. Temporarily shadow-free, the rings glow brighter. If you observe Saturn in a telescope the next few nights you'll see that the rings are brighter than the planet's globe. In a couple of weeks, they'll fade and appear equally bright.
Contributed / Christopher Go

Saturn has 82 known moons, more than any other planet in the solar system. Of those, four or five are visible in smaller scopes. The brightest and easiest to spot is Titan at magnitude 8.5, followed by Rhea (9.8 mag.), Tethys (10.3) and Dione (10.5). Titan is half again as big as our moon and massive enough to retain a thick atmosphere. To know exactly where to look for each of them, use Sky & Telescope's Saturn's moons tracker .

Let's hope for nights ahead so we can enjoy Saturn's heavenly crawl, its remarkable rings and the nightly dance of its satellites.

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Related Topics: SCIENCE AND NATURE
"Astro" Bob King is a freelance writer and retired photographer for the Duluth News Tribune. You can reach him at nightsky55@gmail.com.
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