If I had to pick a single word to describe the system of moons swarming around Saturn as seen by Cassini, it would be "bizarre", "amazing", "exquisite", "jaw-dropping", and "Holy Haleakala!"
[Click to enchronosenate.]
Wow! I love these shots showing perspective! The moon at the top is Rhea, which is about 1500 km (950 miles) across. We’re looking past its south pole here. The moon farther away is Dione, which is 1100 km (700 miles) in size. And since Cassini was very nearly in the plane of Saturn’s equator, the rings are nearly edge-on. Note that Dione is on the other side of the rings as seen by Cassini, so the bottom of the moon is obscured by the rings. We can’t see Saturn itself, but it’s off to the left in this shot.
Rhea is only a little bigger than Dione, but is a lot closer in this shot: 61,000 km versus 924,000 for Dione! That’s why Dione looks so much smaller. As seen by Cassini in this shot, it’s actually more than twice as far as our Moon is from the Earth. Both moons are composed of mostly water ice, with some rock. Both have been heavily battered by impacts, as you can see.
What a gorgeous, spectacular picture. I never get tired of these.
Image credit: NASA/JPL/Space Science Institute
Tip o’ the rings to Carolyn Porco on Twitter.
Related posts:
- The more distant moon
- Dione and Rhea, sitting in a tree
- Two alien worlds, superposed
- Midnight on a ringed world
February 28th, 2011 at 10:52 am
Thanks, Phil. Pictures like this are the main reason I read your blog!
February 28th, 2011 at 10:58 am
Wow, this is an absolutley amazing picture!
February 28th, 2011 at 11:01 am
OK I love that picture, heck I love most all of Cassini’s pictures.
February 28th, 2011 at 11:03 am
Not just obscured by the rings, but it looks like there is even some ring shadow being cast on that moon. Really cool.
February 28th, 2011 at 11:15 am
THAT’S NO MOON! THAT’S A-ctually two moons and the rings of saturn!
February 28th, 2011 at 11:28 am
Cassini is truly an historic mission. These images and the science will provide joy and education for generations to come!
February 28th, 2011 at 11:50 am
@4 Joe R.
That’s probably not a shadow, since it doesn’t follow the curvature of the southern hemisphere of Dione, is too sharp given the distance to Dione from the camera, and is probably too narrow, given the current season on Saturn (not sure about that last part though).
It’s pretty likely a ring of dark material that is only seen in silhouette against the bright background of Dione.
Oh, just noticed: If you click on the image to get the enlarged version, you can see that dark band extending away on either side of Dione, so definitely not a shadow.
February 28th, 2011 at 12:30 pm
Phil,
From the slopes of Haleakala….. many thanks for the plug!
Aloha,
Chris from Maui
February 28th, 2011 at 12:51 pm
Wasn’t it Cassini that they gathered thousands of signatures and digitally put them on board? Just struck me that I couldn’t remember.
Great photo though!
February 28th, 2011 at 1:06 pm
I am sitting with mouth agape at the beauty of the scene.
Wonderful. Wonderful.
February 28th, 2011 at 1:07 pm
Just woke up to such a beautiful photo. Cassini mission is such a wonderful project. My word for this photo is breathtaking
February 28th, 2011 at 1:25 pm
Aloha Chris (#8)… from the observatories on the Big Island of Hawai’i
February 28th, 2011 at 2:30 pm
There’s no stars visible in this picture.
Thus, obviously faked on a Hollywood stage.
Thus, the moon landings never happened.
/agentprovocateur
The hazy ring occultation is amazing. We need more pictures of things seen *rhymesigh* through rings.
February 28th, 2011 at 3:05 pm
Same here. Love these Cassini images. Superluminous.
February 28th, 2011 at 3:06 pm
Wombat, you are on to something. Why, all those Hubble shots are just back lit pieces of cloth with pinholes in them. Get Bill O’Reilly on the case!
February 28th, 2011 at 3:25 pm
@Carey#7
Could that dark line be the F ring, dense enough at this angle to appear solid? It’s also visible – in the enlarged picture – in the foreground below the other rings.
We need Someone Who Knows.
February 28th, 2011 at 3:52 pm
[...] Bad Astronomer Phil Plait says: The moon at the top is Rhea, which is about 1500 km (950 miles) across. We’re looking past its south pole here. The moon farther away is Dione, which is 1100 km (700 miles) in size. And since Cassini was very nearly in the plane of Saturn’s equator, the rings are nearly edge-on. Note that Dione is on the other side of the rings as seen by Cassini, so the bottom of the moon is obscured by the rings. We can’t see Saturn itself, but it’s off to the left in this shot. [...]
February 28th, 2011 at 5:14 pm
Reminds me of the charts for planetary density, ie lighter element body will float on “water” (assuming body of water found that is large enough). This is another reason why we need to get out there. No matter how familiar the planets seem, there is always some thing more interesting out there if viewed in a different way.
I really need to replace the 10″ scope I had access to when growing up.
February 28th, 2011 at 5:25 pm
[...] Peeking past Rhea. [...]
February 28th, 2011 at 6:05 pm
Exactly what is Phil’s fascination with Haleakala, Maui? Great stargazing site? Fascination with Volcanoes? Personal attachment to Hawaii in general? Hmmm…
February 28th, 2011 at 6:36 pm
I don’t intend to steal Phil’s thunder, but I bet a lot of readers would be interested in the sourceblog for these Cassini images:
http://www.ciclops.org/view/6695/Beyond_Southern_Rhea
I have it in my google reader also. I actually really enjoy seeing the images from the Ciclops page and then seeing which ones Phil will comment on.
Ad astra,
Ben H.
Houston, TX
February 28th, 2011 at 7:32 pm
Cassini will surely (or at least ought to be) remembered as one of the most photogenic planetary missions!
Now we have to see if it can spot the Eye of Iapetus!*
*kudos to those that know the reference. I’m sure Phil does!
February 28th, 2011 at 8:55 pm
Correctamundo, Sawdust! That is the F ring!
Now can you BA Blogees see the third moon here?
No BS, there’s 3 moons here.
February 28th, 2011 at 10:47 pm
[QUOTE] We can’t see Saturn itself, but….[/QUOTE]
I take exception to that statement, it should be HER, as in “We can’t see the lovely lady Saturn”.
As you were.
Gorgeous pics by the way.
February 28th, 2011 at 10:48 pm
The Astronomy Bum @ 23: I believe it must be Prometheus, the inner shepherd of the F ring, that can be seen on the near side of the rings (but just inside of the F ring) at about the 4:20 position on Dione. It could also be Pandora, but Prometheus is more elongated, so may bet stays on Prometheus. Pretty neat picture, to understate just a wee bit.
Cheers, Regner
February 28th, 2011 at 11:28 pm
Regner wins! (What does he win?) Bragging rights forever!
W00T!!!
March 1st, 2011 at 3:14 am
Once again, Cassini delivers the Awesome!
Well done (again) to the whole Cassini team!
March 1st, 2011 at 5:50 am
@ Grand Lunar (22) -
My Google-fu tells me it is full of stars.
March 1st, 2011 at 8:32 am
Gentlemen,sorry if this is a dumb question,but could someone explain why Dione being smaller and further away(from Cassini’s POV) than our Moon is to us,looks so big in this picture?
In other words,Luna is almost 3 times bigger and 2 times closer to Earth but doesn’t look this big.Why?
March 1st, 2011 at 1:08 pm
Because Cassini’s narrow-angle camera is essentially a telescope with a CCD camera hooked to it. It gives a magnified view compared to what your eye would see.
March 1st, 2011 at 3:01 pm
Greetings from Saturn…
Take a look at this fantastic picture from the Cassini probe with parts of Saturn’s rings and the moons Rhea and Dione: Credit: NASA/JPL/Space Science Institute Sometimes I get in a bad mood, when I see what humans do to each other or to nature, but th…
March 1st, 2011 at 4:39 pm
The next moon out from Rhea really should have been named Ghonnor, what fun that would have been. What not funny? I bet you all laughed at Uranus.
March 1st, 2011 at 5:13 pm
Thanks for the answer Tom F. ,even though after reading it , i feel dumb and ashamed.Cheers.
March 2nd, 2011 at 2:52 am
I will never ever get tired of the beautiful photos Cassini keeps sending us. It’s sad knowing it’ll only last until 2017.
March 2nd, 2011 at 7:02 am
[...] Enlarge. | Via. [...]