APOD: Cassini Spacecraft Crosses Saturn's... (2010 Feb 15)

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APOD Robot
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APOD: Cassini Spacecraft Crosses Saturn's... (2010 Feb 15)

Post by APOD Robot » Mon Feb 15, 2010 5:13 am

Image Cassini Spacecraft Crosses Saturn's Ring Plane

Explanation: If this is Saturn, where are the rings? When Saturn's "appendages" disappeared in 1612, Galileo did not understand why. Later that century, it became understood that Saturn's unusual protrusions were rings and that when the Earth crosses the ring plane, the edge-on rings will appear to disappear. This is because Saturn's rings are confined to a plane many times thinner, in proportion, than a razor blade. In modern times, the robot Cassini spacecraft orbiting Saturn now also crosses Saturn's ring plane. A series of plane crossing images from late 2005 February was dug out of the vast online Cassini raw image archive by interested Spanish amateur Fernando Garcia Navarro. Pictured above, digitally cropped and set in representative colors, is the striking result. Saturn's thin ring plane appears in blue, bands and clouds in Saturn's upper atmosphere appear in gold. Since Saturn just passed its equinox, today the ring plane is pointed close to the Sun and the rings could not cast the high dark shadows seen across the top of this image, taken back in 2005. Moons appear as bumps in the rings.

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Lasse H
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Re: APOD: Cassini Spacecraft Crosses Saturn's... (2010 Feb 1

Post by Lasse H » Mon Feb 15, 2010 10:59 am

Why put a photo of the rings, taken in February, together with a background of Saturn taken in 2005? Very confusing, especially since it's pointed out that it could not look like it does in the picture.

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RedFishBlueFish
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Re: APOD: Cassini Spacecraft Crosses Saturn's... (2010 Feb 1

Post by RedFishBlueFish » Mon Feb 15, 2010 11:39 am

:?: The horizontal blue line would be the rings edge-on then :?:

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RJN
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Re: APOD: Cassini Spacecraft Crosses Saturn's... (2010 Feb 1

Post by RJN » Mon Feb 15, 2010 1:19 pm

Two typos corrected. Try it now. - RJN

Lasse H
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Re: APOD: Cassini Spacecraft Crosses Saturn's... (2010 Feb 1

Post by Lasse H » Mon Feb 15, 2010 1:50 pm

Thanks! Now I understand. /LH

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Re: APOD: Cassini Spacecraft Crosses Saturn's... (2010 Feb 1

Post by bdb_raclub » Mon Feb 15, 2010 4:00 pm

Please look again, we do see the rings' shadows on the upper half of the iimage. They are consistent with the angle of the terminator on the planet. Saturn is around equnox now but not when Casini made the image in 2005. Casini does not have to wait for equinox to cross the ring plane and get an edge-on view.

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bystander
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Re: APOD: Cassini Spacecraft Crosses Saturn's... (2010 Feb 1

Post by bystander » Mon Feb 15, 2010 6:00 pm

bdb_raclub wrote:Please look again, we do see the rings' shadows on the upper half of the iimage. They are consistent with the angle of the terminator on the planet. Saturn is around equnox now but not when Casini made the image in 2005. Casini does not have to wait for equinox to cross the ring plane and get an edge-on view.
We can see the rings' shadows, when they are present. The picture shown was taken in 2005 and the shadows are plainly visible, but LH's point was, since Saturn has just passed equinox, the shadows shouldn't be that visible now. The confusion was in the original wording of the explanation, which made it seem like the picture was taken this month.

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DavidLeodis
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Re: APOD: Cassini Spacecraft Crosses Saturn's... (2010 Feb 1

Post by DavidLeodis » Tue Feb 16, 2010 11:37 am

There are what I assume are 2 moons of Saturn visible. I would be grateful if someone could name them, if that is possible to know from the image. :?: Thanks. :)

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Re: APOD: Cassini Spacecraft Crosses Saturn's... (2010 Feb 1

Post by neufer » Tue Feb 16, 2010 4:09 pm

DavidLeodis wrote:There are what I assume are 2 moons of Saturn visible. I would be grateful if someone could name them, if that is possible to know from the image. :?: Thanks. :)
The usual suspects:
Image
http://www.youtube.com/watch?v=GqwUpABqYBo
Art Neuendorffer

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DavidLeodis
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Re: APOD: Cassini Spacecraft Crosses Saturn's... (2010 Feb 1

Post by DavidLeodis » Tue Feb 16, 2010 5:54 pm

Thanks neufer. I thought it would be unlikely that the moons could be named with certainty. I guess they will be 2 of the large moons near Saturn.

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Re: APOD: Cassini Spacecraft Crosses Saturn's... (2010 Feb 1

Post by emc » Wed Feb 17, 2010 2:43 pm

APOD Robot wrote:Image Cassini Spacecraft Crosses Saturn's Ring Plane

Explanation: If this is Saturn, where are the rings? ...
Image

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Re: APOD: Cassini Spacecraft Crosses Saturn's... (2010 Feb 1

Post by geckzilla » Fri Aug 08, 2014 7:37 am

DavidLeodis wrote:There are what I assume are 2 moons of Saturn visible. I would be grateful if someone could name them, if that is possible to know from the image. :?: Thanks. :)
Owlice asked me this tonight and I dug until I found the exact time and day of the exposures. 2005 Feb 28th 16:49 UTC. From there you can use Solar System Simulator to find out which moons were in that spot at that time.
http://space.jpl.nasa.gov/
With the right parameters, you get this.
satsim_apod_investigation.jpg
It's Dione and Enceladus. I posted a bit longer explanation on my quest for the answers here.
You do not have the required permissions to view the files attached to this post.
Just call me "geck" because "zilla" is like a last name.

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Re: APOD: Cassini Spacecraft Crosses Saturn's... (2010 Feb 1

Post by owlice » Fri Aug 08, 2014 7:38 am

Yay, geckzilla!!! Excellent sleuthing; thank you!! :clap:
A closed mouth gathers no foot.

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DavidLeodis
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Re: APOD: Cassini Spacecraft Crosses Saturn's... (2010 Feb 1

Post by DavidLeodis » Fri Aug 08, 2014 11:01 am

Thanks for your help geckzilla, which is much appreciated. :)

When I read the email notifying me that there had been a new post to a thread that I was interested in I was quite surprised to see that the thread was from 2010! It's almost like astroarchaeology (if there is such a word :P ) in finding the answer! As owlice states, it is "Excellent sleuthing". :thumb_up: