APOD: Crescent Saturn (2019 Jul 07)

[APOD Robot]

Crescent Saturn

Explanation: Saturn never shows a crescent phase -- from Earth. But when viewed from beyond, the majestic giant planet can show an unfamiliar diminutive sliver. This image of crescent Saturn in natural color was taken by the robotic Cassini spacecraft in 2007. The featured image captures Saturn's majestic rings from the side of the ring plane opposite the Sun -- the unilluminated side -- another vista not visible from Earth. Pictured are many of Saturn's photogenic wonders, including the subtle colors of cloud bands, the complex shadows of the rings on the planet, and the shadow of the planet on the rings. A careful eye will find the moons Mimas (2 o'clock) and Janus (4 o'clock), but the real challenge is to find Pandora (8 o'clock). Saturn is now nearly opposite from the Sun in the Earth's sky and so can be seen in the evening starting just after sunset for the rest of the night.

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[ecdowney]

Ok, I give up. Where is Pandora?

[DL MARTIN]

As well.

[mfavret]

Hi !
I'm french and I hope you will excuse my poor English.
It's better in full size :

[atrin]

There is also something at 9 o'clock (inside outer ring) and at 7 o'clock (just outside outer ring like Pandora)

[mfavret]

Position in the picture :

[orin stepanek]

What a wonderful probe Cassini was! It did a marvelous job exploring Saturn and it's moons and rings!

[PharAstro]

Pardon me if these are stupid questions. 1) The shadow on the rings seems too skinny and inconsistent with the very long, conical shadow (almost cylindrical, I guess) that would have it's base at the day/night terminator. Can someone explain? 2) From the shadow of the rings on the planet, it would appear that the sun is "below" the rings (opposite hemisphere from the camera). But there is a region of dim glow that appears to be above the rings and on the night side. Is it "ring shine", analogous to earth shine during the new moon? Thanks.

[sunson]

Questions:
1- How come there are two outermost rings on the left side but they become one towards the right?
2- How come the upper shadow line on the rings bulges upward?
3- Why the outer most ring(s) vary in whiteness (reflection)?

[neufer]

1- How come there are two outermost rings on the left side but they become one towards the right?

<<The F Ring is the outermost discrete ring of Saturn and perhaps the most active ring in the Solar System, with features changing on a timescale of hours. It is located 3,000 km beyond the outer edge of the A ring. The ring was discovered in 1979 by the Pioneer 11 imaging team. It is very thin, just a few hundred km in radial extent. While the traditional view has been that it is held together by two shepherd moons, Prometheus and Pandora, which orbit inside and outside it, recent studies indicate that only Prometheus contributes to the confinement. Numerical simulations suggest the ring was formed when Prometheus and Pandora collided with each other and were partially disrupted.

A mosaic of 107 images showing 255° (about 70%) of the F Ring as it would appear if straightened out, showing the kinked primary strand and the spiral secondary strand. The radial width (top to bottom) is 1,500 km.

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More recent closeup images from the Cassini probe show that the F Ring consists of one core ring and a spiral strand around it. They also show that when Prometheus encounters the ring at its apoapsis, its gravitational attraction creates kinks and knots in the F Ring as the moon 'steals' material from it, leaving a dark channel in the inner part of the ring. Since Prometheus orbits Saturn more rapidly than the material in the F ring, each new channel is carved about 3.2 degrees in front of the previous one.>>

[Boomer12k]

Always good to see Saturn...

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