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SYFY WIRE Bad Astronomy

The Immense Beauty of Saturn

By Phil Plait

On Aug. 19, 2012, the hardest-working spacecraft in the solar system, Cassini, was 2.4 million kilometers (1.5 million miles) from Saturn when it snapped this overwhelming portrait of the ringed planet:

Man, I love these greyscale shots. Theyâre so moody.

Right now itâs summer in Saturnâs northern hemisphereâthough at 1.4 billion kilometers (900 million miles) from the Sun and temperatures of -150 degrees Celsius (-240 degrees Fahrenheit) and lower, the term âsummerâ is definitely relativeâwith the Sun shining down on the rings from the north. Cassini was below the ring plane in this shot, looking up at them, so they appear a bit darker than they would if Cassini were above them looking down.

As you can see, Saturn has lots of rings; thousands, in fact! The rings are not solid, but instead composed of countless small pieces of nearly pure water ice, the biggest probably smaller than an average house. Some of the rings are extremely narrow, too: You can see the thin ones silhouetted against the face of the planet itself, looking like piano wires strung across the vast cloudscape.

Just below and to the right of the rings you can see their shadow on the cloud tops of Saturn. Iâm fascinated by the play of light and shadow on the rings and the planet, highlighting the complexity of the rings. You can also see some storms in the clouds on Saturn; that dark circular one with the bright rim around it is about 4,000 kilometers (2,400 miles) acrossâabout as wide as the continental United States!

Saturn is big.

So big, I suspect, that you might have missed the tiny spark of light in the upper left. Thatâs Saturnâs moon Tethys, seen here a little more than half full as itâs lit by the distant Sun. But itâs hardly tiny: Itâs nearly 1,100 kilometers (660 miles) across, about the distance from Chicago to Washington, D.C.!

Our sense of size is dwarfed by objects on this scale. And yet, there we are. Cassini has been circling Saturn and flying past its weird moons since 2004, returning vast amounts of data about the planet and its environment. But for all the knowledge gained, and more yet to come, when I see pictures like this I sometimes wonder if the most important thing Cassini has done is shown us how starkly beautiful and immense our solar system is.

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