Ringless Saturn

It’s 2 am. You wake up in the middle of the night. You have a plan. You want to see Saturn. You go outside and look up. Good, the sky is clear. You can see Leo the Lion rising above the eastern horizon. Near the Lion’s tail, you see a bright yellowish “star”. You know that’s Saturn. You point your little 4.5-inch telescope at the ringed planet, longing to see its magnificent rings again.

Something is not right…

You look up at the sky again. You refer to a star chart. You re-aim and look through your scope again. You are very sure that the bright disk you see is Saturn, but that’s not the planet you’re expecting to see. All you see is a just a bright round disk…

Where are the rings???

No fear, the rings are still there, just that they are not so easily visible nowadays on Earth.

What happen is that now we are approaching a time called the “ring plane crossing” period. This is the time when Saturn’s rings appear edge-on to us and disappeared from view.


As seen from Earth, Saturn’s rings are tilted at an angle of 27 degrees. As the planet orbits around the Sun, there will be times when the rings are tilted maximum to us, and times when we will see the rings edge-on. And since Saturn’s rings are so thin (about 0.2 to 3 km only!), when they are edge-on, the rings just disappear from sight.

We are now only approaching the ring plane crossing and not there yet. The precise ring plane crossing (opening angle of the rings = 0 degree) won’t happen until September 4, 2009.

Currently, the opening angle of the rings is about 1 degree. In January next year, the rings will temporary open up again until mid-May to a maximum of 4 degrees due to the orbital motion of our planet and the ringed planet, before it narrows down to zero degree in September. But don’t wait until then to see “naked Saturn” though, because the planet will be too close to the Sun to observe.

So the best time to not see Saturn rings is right now!

And since the rings are not totally edge-on now, if the sky is clear and the atmosphere is steady, look carefully and you might catch a glimpse of the shadowy thin rings cutting Saturn into halves.

Edge-on Saturn by Paulo Casquinha

Edge-on Saturn: amateur astronomer Paulo Casquinha took this picture on Dec 25, 2008 from his backyard observatory in Quinta do Anjo, Portugal. Extract from SpaceWeather.com


~ by thChieh on December 30, 2008.

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