2024, November 29: Saturn is Dimmer than Usual

November 29, 2024:  Planet Saturn is dimmer than usual.  Its rings reflect considerable light that contributes to its brightness in the night sky.

Saturn
Image Caption – This NASA Hubble Space Telescope photo of Saturn reveals the planet’s cloud bands and a phenomenon called ring spokes.

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by Jeffrey L. Hunt

Chicago, Illinois: Sunrise, 6:57 a.m. CDT; Sunset, 4:21 p.m. CST.  Check local sources for sunrise and sunset times. Times are calculated by the US Naval Observatory’s MICA computer program.

Saturn, Solar System’s Jewel

Saturn through the Hubble Space Telescope
Photo Caption – A Hubble View of Saturn (NASA)

Saturn is the jewel of the solar system. It dazzles through a telescope – a yellow orange planet with a set of bright icy rings. Unlike Jupiter, Saturn’s cloud stripes are muted by a high level of aerosols. The first view of the planet is memorable.  The planet, though, is dimmer than usual.

Saturn’s Moons

Slipping into shadow, the south polar vortex at Saturn's moon Titan still stands out against the orange and blue haze layers that are characteristic of Titan's atmosphere. Images like this, from NASA's Cassini spacecraft, lead scientists to conclude that the polar vortex clouds form at a much higher altitude -- where sunlight can still reach -- than the lower-altitude surrounding haze.
Chart Caption – Slipping into shadow, the south polar vortex at Saturn’s moon Titan still stands out against the orange and blue haze layers that are characteristic of Titan’s atmosphere. Images like this, from NASA’s Cassini spacecraft, lead scientists to conclude that the polar vortex clouds form at a much higher altitude — where sunlight can still reach — than the lower-altitude surrounding haze. (NASA Photo)

Saturn has an armada of about 150 moons, eight of which are visible through backyard telescopes.

Saturn’s Unusual Characteristics

 The planet’s globe is not a perfect sphere, but it is flattened by its rapid rotation, 10 hours, 39 minutes. Its equatorial diameter is noticeably longer than its polar length. If the planet were empty, it could hold over 800 Earths.

We can estimate Saturn’s mass by observing the speed at which its satellites orbit. For example, Titan, Saturn’s largest moon, orbits the planet in nearly 16 days at a distance more than three times that of Earth’s moon. This gravitational relationship indicates that Saturn’s mass is over 90 times that of Earth.

Saturn floating in a bathtub
Image Caption – Saturn floating in a bathtub – generated by AI

This mass in combination with its volume predicts that the planet has a density less than water, meaning that in a sufficiently large tub of water, it could float.

The Rings

A closeup of Saturn's rings from the Cassini spacecraft.
Photo Caption – A closeup of Saturn’s rings from the Cassini spacecraft (NASA photo).

Its famous rings are composed of ices, ranging in sizes from tiny particles to boulders.  The rings have three distinct sections visible through backyard telescopes. The outermost is designated as the “A” ring.  It is separated from the “B” ring by a gap, first observed in 1675 by J.D. Cassini, now known as the Cassini Division.

The B ring is widest and the rings’ brightest sector. It meets the dimmer “C” ring that mostly goes unnoticed.

Saturn’s 30-year Orbit

Saturn's orbit
Chart caption – Saturn moves through its orbit.

Like Earth, Saturn is tilted compared to its orbital plane, at 26.7°.  During its nearly 30-year trek around the sun, the planet experiences seasons so that the poles are alternately displayed toward the sun.  In between, the equator receives the sun’s feeble light.

During Saturn’s summer season in its northern hemisphere, earth-based sky watchers see the top of the rings.  During winter, we see the bottom or southside of the rings.  When the equinoxes occur on Saturn, we see the rings edge on, a ring-plane crossing, on March 23rd. The next one does not occur until 2039.

Saturn is Dimmer than Usual

Currently the rings have a shallow angle with our view and so they do not reflect much light toward Earth.  Saturn watchers are noticing that the planet is not as bright as they typically see it.  During the early evening hours, Saturn is in the southern sky in front of Aquarius and to the upper left of Fomalhaut, the mouth of the Southern Fish.  It is the brightest starlike body in the sky.

If you have not seen Saturn through a telescope, visit your local planetarium during a telescope night or find your local astronomy club during one of their public nights.  Better yet, ask your neighborhood sky watcher to show you Saturn through their telescope.  The planet is nicely placed after sunset for a pretty view.

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