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APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 5:05 am
by APOD Robot
In the Shadow of Saturn
Explanation: In the shadow of Saturn, unexpected wonders appear. The
robotic Cassini spacecraft now orbiting
Saturn drifted in giant planet's
shadow earlier this year and looked back toward the
eclipsed Sun. Cassini saw a unique and celebrated
view. First, the
night side of Saturn is seen to be partly lit by light reflected from its own
majestic ring system. Next, Saturn's expansive ring system appears as majestic as always even from this odd angle. Ring particles, many glowing only as irregular crescents,
slightly scatter sunlight toward Cassini in this
natural color image. Several
moons and ring features are also discernible. Appearing quite prominently is Saturn's
E ring, the ring created by the unusual
ice-fountains of the moon
Enceladus and the outermost ring visible above. To the upper left, far in the distance, are the planets Mars and Venus. To the lower right, however, is perhaps the most wondrous spectacle of all: the almost invisible, nearly ignorable,
pale blue dot of Earth.
[/b]
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 5:07 am
by geckzilla
Highest resolution version without annotation here:
http://photojournal.jpl.nasa.gov/figure ... 2_fig1.jpg
Highest resolution version with more detailed annotation here:
http://photojournal.jpl.nasa.gov/figure ... 2_fig3.jpg
They're in the description links but just in case you missed them.
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 6:32 am
by Nitpicker
With a father like Ouranos, I always knew Saturn would have a beautiful backside. Thank you again, APOD, Asterisk, Cassini Imaging Team and everyone else involved in making it possible to behold this incredible image.
Naturally, I have a question, but I wouldn't call it a nitpick this time, and most certainly not a criticism. It is just a bona fide question from a curious admirer. I have just read a more detailed description of this image here:
http://www.ciclops.org/view/7699/The-Da ... miled?js=1
But I still cannot figure out the narrow black crescent which outlines the top of the planet, and how it appears
on the outside of the thin white ring of light which virtually encircles the planet. Is this an instantaneous effect, or the consequence of combining hundreds of component images taken over a period of four hours?
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 7:08 am
by Mactavish
An amazing image. Simply amazing!
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 7:24 am
by gwrede
The annotation says "Earth and Moon" and points to a white dot.
To me, that says that they both are where pointed, but I can't seem to find the Moon near the Earth. Maybe it's behind the Earth? But that is unlikely.
Therefore, I'd prefer the annotation to only mention the Earth. If somebody doesn't understand that this implies the Moon is "somewhere in the vicinity", then that's outside the scope of annotations for this picture.
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 7:43 am
by alter-ego
Nitpicker wrote:
... But I still cannot figure out the narrow black crescent which outlines the top of the planet, and how it appears on the outside of the thin white ring of light which virtually encircles the planet. Is this an instantaneous effect, or the consequence of combining hundreds of component images taken over a period of four hours?
It is not an instantaneous effect. It's as you said, due to combination of hundreds (141 of 323) images taken over 4 hours.
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 7:46 am
by alter-ego
gwrede wrote:The annotation says "Earth and Moon" and points to a white dot.
To me, that says that they both are where pointed, but I can't seem to find the Moon near the Earth. Maybe it's behind the Earth? But that is unlikely.
Therefore, I'd prefer the annotation to only mention the Earth. If somebody doesn't understand that this implies the Moon is "somewhere in the vicinity", then that's outside the scope of annotations for this picture.
Both the Earth and Moon are visible in the highest resolution (not annotated) picture:
![Zoomed in view of Earth and Moon](./download/file.php?id=11285&sid=c2af5a6d43fb4169af11f2895915c651)
- Zoomed in view of Earth and Moon
- Earth & Moon_Highest Resolution.JPG (8.08 KiB) Viewed 7304 times
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 7:52 am
by Boomer12k
Always an awesome sight...the beauty of the Solar System...and the concept of looking back at us is just amazing!!!
:---[===] *
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 9:10 am
by Nitpicker
alter-ego wrote:Nitpicker wrote:
... But I still cannot figure out the narrow black crescent which outlines the top of the planet, and how it appears on the outside of the thin white ring of light which virtually encircles the planet. Is this an instantaneous effect, or the consequence of combining hundreds of component images taken over a period of four hours?
It is not an instantaneous effect. It's as you said, due to combination of hundreds (141 of 323) images taken over 4 hours.
Thank you alter-ego. That's good enough for me. I've noticed that every time we've attempted to correct each other previously, I was wrong and you were right.
![:) :ssmile:](./images/smilies/smile.gif)
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 9:23 am
by Patrick60
Is that Jupiter at the lower left, visible as a disc at about 8 o'clock?
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 11:57 am
by Indigo_Sunrise
I saw this in the email announcement from
ciclops.org and I am in absolutely gobsmacked at the resolution and clarity. This image is my favorite:
Saturn 38754, but only because it's got everything labeled.
(The unlabeled images are uber-fabulous too.)
Two thumbs way up for the Cassini Team!
![thumb up :thumb_up:](./images/smilies/thumb_up.gif)
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 12:00 pm
by Indigo_Sunrise
Patrick60, according to the image in
this link, I believe what you're asking about is one of Saturn's moons, Tethys.
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 12:13 pm
by Cousin Ricky
Nitpicker wrote:But I still cannot figure out the narrow black crescent which outlines the top of the planet, and how it appears on the outside of the thin white ring of light which virtually encircles the planet. Is this an instantaneous effect, or the consequence of combining hundreds of component images taken over a period of four hours?
I figured it's the shadow of the planet, projected onto the ring particles. Since Cassini was inside the umbra, the shadow projection would
appear larger than the planet itself. Of course, I can count on someone to teach me something new if I'm wrong.
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 1:31 pm
by neufer
Cousin Ricky wrote:Nitpicker wrote:
I still cannot figure out the narrow black crescent which outlines the top of the planet, and how it appears on the outside of the thin white ring of light which virtually encircles the planet. Is this an instantaneous effect, or the consequence of combining hundreds of component images taken over a period of four hours?
I figured it's the shadow of the planet, projected onto the ring particles. Since Cassini was inside the umbra, the shadow projection would
appear larger than the planet itself. Of course, I can count on someone to teach me something new if I'm wrong.
It is certainly the shadow but it shows up only
above Saturn because the Sun is slightly
below the point directly behind Saturn.
The Sun is
almost a point source at this distance and will not produce a noticeable penumbra at this resolution.
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 1:41 pm
by CygnusOB2
A serious contender for my all-time favourite solar system image. Wow !!
![Very Happy :D](./images/smilies/icon_biggrin.gif)
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 3:56 pm
by alter-ego
Nitpicker wrote:
... I've noticed that every time we've attempted to correct each other previously, I was wrong and you were right.
![:) :ssmile:](./images/smilies/smile.gif)
Well, in this example I thought I was just agreeing with you
![Wink :wink:](./images/smilies/icon_wink.gif)
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 4:38 pm
by searaycuddy
The moon can be seen by most PC users by maximizing the image and then magnifying the image further by using key strokes of "control +". Use your slide bars on the side and bottom to locate Earth. Try it, you'll like it.
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 4:41 pm
by Chris Peterson
alter-ego wrote:Both the Earth and Moon are visible in the highest resolution (not annotated) picture:
![Image](http://asterisk.apod.com/download/file.php?id=11285)
Note, however, that neither object is resolved. Both are optical point sources, and the apparent sizes are purely a function of diffraction and their relative brightnesses. The NAC camera used has a pixel scale of 1.2 arcseconds; on the date this image was made, the Earth subtended 1.8 arcsec, and the Moon subtended 0.5 arcsec.
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 4:44 pm
by MTD
neufer wrote:Cousin Ricky wrote:Nitpicker wrote:
I still cannot figure out the narrow black crescent which outlines the top of the planet, and how it appears on the outside of the thin white ring of light which virtually encircles the planet. Is this an instantaneous effect, or the consequence of combining hundreds of component images taken over a period of four hours?
I figured it's the shadow of the planet, projected onto the ring particles. Since Cassini was inside the umbra, the shadow projection would
appear larger than the planet itself. Of course, I can count on someone to teach me something new if I'm wrong.
It is certainly the shadow but it shows up only
above Saturn because the Sun is slightly
below the point directly behind Saturn.
The Sun is
almost a point source at this distance and will not produce a noticeable penumbra at this resolution.
The black crescent is Saturn's shadow on the half of the rings closest to Cassini. The shadow shows up only
above Saturn because the rings
below Saturn are on the other side of Saturn from Cassini's point of view, closer to the Sun, where Saturn can't cast a shadow.
The thin white ring that encircles Saturn is sunlight shining through Saturn's upper atmosphere. The black crescent shadow appears
on the outside of the thin ring of atmosphere because the crescent shadow is the shadow of Saturn on the rings closest to Cassini. Parts of the thin ring are less bright because it's blocked by shadows cast by the rings, on the lower half of Saturn, or by the rings themselves, on the upper half.
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 5:10 pm
by neufer
Nitpicker wrote:
I still cannot figure out the narrow black crescent which outlines the top of the planet, and how it appears on the outside of the thin white ring of light which virtually encircles the planet. Is this an instantaneous effect, or the consequence of combining hundreds of component images taken over a period of four hours?
MTD wrote:neufer wrote:Cousin Ricky wrote:
I figured it's the shadow of the planet, projected onto the ring particles. Since Cassini was inside the umbra, the shadow projection would appear larger than the planet itself. Of course, I can count on someone to teach me something new if I'm wrong.
It is certainly the shadow but it shows up only
above Saturn because the Sun is slightly
below the point directly behind Saturn.
The Sun is
almost a point source at this distance and will not produce a noticeable penumbra at this resolution.
The black crescent is Saturn's shadow on the half of the rings closest to Cassini. The shadow shows up only
above Saturn because the rings
below Saturn are on the other side of Saturn from Cassini's point of view, closer to the Sun, where Saturn can't cast a shadow.
The thin white ring that encircles Saturn is sunlight shining through Saturn's upper atmosphere. The black crescent shadow appears
on the outside of the thin ring of atmosphere because the crescent shadow is the shadow of Saturn on the rings closest to Cassini. Parts of the thin ring are less bright because it's blocked by shadows cast by the rings, on the lower half of Saturn, or by the rings themselves, on the upper half.
Okily Dokily.
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 7:11 pm
by quigley
Absolutely amazing image, and in natural colors. Is there a way to get a print of it, preferably in its highest resolution? I'd love to have it up on my office wall to stare and marvel at.
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 7:36 pm
by geckzilla
quigley wrote:Absolutely amazing image, and in natural colors. Is there a way to get a print of it, preferably in its highest resolution? I'd love to have it up on my office wall to stare and marvel at.
It would be a simple matter to download the high resolution TIFF file provided and get it printed using any of a number of online print services. You could also save it to a CD or a flash drive and take it to your local print shop.
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 7:53 pm
by Anthony Barreiro
quigley wrote:Absolutely amazing image, and in natural colors. Is there a way to get a print of it, preferably in its highest resolution? I'd love to have it up on my office wall to stare and marvel at.
All NASA images are in the public domain. You could
download a high resolution image and take it to
your local print shop or use
an online printing service to make yourself a poster-sized print. You could even add an inspiring quote, and
sell prints online. I might buy one.
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 7:58 pm
by Beyond
Just don't say... The Uranus side of Saturn, or something similar.
![Mr. Green :mrgreen:](./images/smilies/icon_mrgreen.gif)
Re: APOD: In the Shadow of Saturn (2013 Nov 13)
Posted: Wed Nov 13, 2013 8:03 pm
by Anthony Barreiro
Every time I look at this image, I'm intrigued by the fact that some of the rings seen against the dark face of Saturn do not line up with the rings as seen against the background of space. I understand that the rings between Cassini and Saturn are being illuminated by light reflected and perhaps refracted from the rings that are in direct sunlight. But it tickles my mind to notice that I automatically try to decide where the rings "really" are.