APOD: A Close Pass of Saturns Moon Dione (2012 May 21)

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APOD: A Close Pass of Saturns Moon Dione (2012 May 21)

Postby APOD Robot » Mon May 21, 2012 4:07 am

Image A Close Pass of Saturns Moon Dione

Explanation: What's that past Dione? When making its closest pass yet of Saturn's moon Dione late last year, the robotic Cassini spacecraft snapped this far-ranging picture featuring Dione, Saturn's rings, and the two small moons Epimetheus and Prometheus. The above image captures part of the heavily cratered snow-white surface of the 1,100 kilometer wide Dione, the thinness of Saturn's rings, and the comparative darkness of the smaller moon Epimetheus. The image was taken when Cassini was only about 100,000 kilometers from the large icy moon. Future events in Cassini's continuing exploration of Saturn and its moons include tomorrow's flyby of Titan and imaging the distant Earth passing behind Saturn in June.

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Re: APOD: A Close Pass of Saturns Moon Dione (2012 May 21)

Postby bystander » Mon May 21, 2012 4:22 am

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Re: APOD: A Close Pass of Saturns Moon Dione (2012 May 21)

Postby owlice » Mon May 21, 2012 4:32 am

What a stunning photo! Breath-taking!
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Re: APOD: A Close Pass of Saturns Moon Dione (2012 May 21)

Postby orin stepanek » Mon May 21, 2012 12:02 pm

Nice jot Cassini! 8-) :saturn: :thumb_up: :thumb_up: I also liked the comparative darkness picture! :D Aww!
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After thought: EpiMEtheus is brighter than he looks!

Postby neufer » Mon May 21, 2012 1:45 pm

APOD Robot wrote:Image A Close Pass of Saturns Moon Dione

Explanation: What's that past Dione? When making its closest pass yet of Saturn's moon Dione late last year, the robotic Cassini spacecraft snapped this far-ranging picture featuring Dione, Saturn's rings, and the two small moons Epimetheus and Prometheus. The above image captures part of the heavily cratered snow-white surface of the 1,100 kilometer wide Dione, the thinness of Saturn's rings, and the comparative darkness of the smaller moon Epimetheus. The image was taken when Cassini was only about 100,000 kilometers from the large icy moon. Future events in Cassini's continuing exploration of Saturn and its moons include tomorrow's flyby of Titan and imaging the distant Earth passing behind Saturn in June.

<<In his book Commemorating Epimetheus (2009), Les Amis credits Epimetheus with bringing to the world our knowledge of dependency on each other described phenomenologically in terms of sharing, caring, meeting and dwelling and loving.>>

Epimetheus: Albedo= 0.73 :!: / Mean density= 0.64 g/cm³
Prometheus: Albedo= 0.60 / Mean density= 0.48 g/cm³

http://en.wikipedia.org/wiki/Epimetheus_%28mythology%29 wrote:
<<In Greek mythology, Epimetheus (Ἐπιμηθεύς: "hindsight", literally "afterthinker,") was the brother of Prometheus (Προμηθεύς: "foresight", literally "fore-thought"), a pair of Titans who "acted as representatives of mankind". They were the inseparable sons of Iapetus, who in other contexts was the father of Atlas. While Prometheus is characterized as ingenious and clever, Epimetheus is depicted as foolish.

According to Plato's use of the old myth in his Protagoras (320d-322a), the twin Titans were entrusted with distributing the traits among the newly-created animals. Epimetheus was responsible for giving a positive trait to every animal, but when it was time to give man a positive trait, lacking foresight he found that there was nothing left.

Prometheus decided that mankind's attributes would be the civilizing arts and fire, which he stole from Zeus. Prometheus later stood trial for his crime. In the context of Plato's dialogue, "Epimetheus, the being in whom thought follows production, represents nature in the sense of materialism, according to which thought comes later than thoughtless bodies and their thoughtless motions."

According to Hesiod, who related the tale twice (Theogony, 527ff), Epimetheus was the one who accepted the gift of Pandora from the gods. Their marriage may be inferred (and was by later authors), but it is not made explicit in either text.

Epimetheus plays a key role in the philosophy of Bernard Stiegler, and in particular in terms of his understanding of the relation between technogenesis and anthropogenesis. According to Stiegler, it is significant that Epimetheus is entirely forgotten in the philosophy of Martin Heidegger. In his book Commemorating Epimetheus (2009), [Les Amis credits Epimetheus] with bringing to the world our knowledge of dependency on each other described phenomenologically in terms of sharing, caring, meeting and dwelling and loving.>>
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Saturn Rings

Postby Fran » Mon May 21, 2012 3:19 pm

The rings of Saturn are at an angle that seems to defy gravitational pull -- I'd expected them to be located at an equatorial center of gravity. Would someone please explain how the rings can exist given the angle shown on the Picture of the Day for May 21, 2012? Thank you!
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Re: Saturn Rings

Postby neufer » Mon May 21, 2012 3:29 pm

Fran wrote:
The rings of Saturn are at an angle that seems to defy gravitational pull -- I'd expected them to be located at an equatorial center of gravity. Would someone please explain how the rings can exist given the angle shown on the Picture of the Day for May 21, 2012? Thank you!

Look again, Fran. You can't see Saturn at all in the Picture of the Day for May 21, 2012.
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Re: APOD: A Close Pass of Saturns Moon Dione (2012 May 21)

Postby Fran » Mon May 21, 2012 4:29 pm

Hah! I completely misunderstood what I was looking at. Thank you, Art.
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Re: APOD: A Close Pass of Saturns Moon Dione (2012 May 21)

Postby starstruck » Mon May 21, 2012 9:25 pm

Cassini does it again . . another great shot :!:
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Re: APOD: A Close Pass of Saturns Moon Dione (2012 May 21)

Postby Moonlady » Mon May 21, 2012 9:44 pm

What is allowed on Dione?

Here I found a sign:
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Re: APOD: A Close Pass of Saturns Moon Dione (2012 May 21)

Postby ta152h0 » Mon May 21, 2012 10:15 pm

In June, when Cassini observes the Earth, any plans like shooting a giant laserbeam and see if Cassini sees it ? or any other experiments the the big poobah at JPL can think of ?
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Re: APOD: A Close Pass of Saturns Moon Dione (2012 May 21)

Postby neufer » Mon May 21, 2012 10:27 pm

ta152h0 wrote:
In June, when Cassini observes the Earth, any plans like shooting a giant laserbeam and see if Cassini sees it ? or any other experiments the the big poobah at JPL can think of ?

With a very narrow bandwidth filter and the ability to detect and accumulate a very large number of short duration pulses it might just be possible for a Cassini like space craft to detect a laser signal from the Earth. There is no way the current Cassini could do so, however.
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Re: APOD: A Close Pass of Saturns Moon Dione (2012 May 21)

Postby ta152h0 » Mon May 21, 2012 10:51 pm

So a salute with an ice cold one in hand is definitaly out !!! :(
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Re: APOD: A Close Pass of Saturns Moon Dione (2012 May 21)

Postby neufer » Tue May 22, 2012 12:02 am

ta152h0 wrote:
So a salute with an ice cold one in hand is definitely out !!! :(

    It wouldn't be the first time.
http://en.wikipedia.org/wiki/Communicat ... ce#History wrote:
<<In the nineteenth century... many people believed that intelligent beings might live on the Moon, Mars, and Venus; but since travel to other planets was not yet possible, some people suggested ways to signal the extraterrestrials even before radio was discovered.

Carl Friedrich Gauss suggested that a giant triangle and three squares, the Pythagoras, could be drawn on the Siberian tundra. The outlines of the shapes would have been ten-mile wide strips of pine forest, the interiors could be rye or wheat.

Joseph Johann Littrow proposed using the Sahara as a blackboard. Giant trenches several hundred yards wide could delineate twenty-mile wide shapes. Then the trenches would be filled with water, and then enough kerosene could be poured on top of the water to burn for six hours. Using this method, a different signal could be sent every night.

The inventor Charles Cros was convinced that pinpoints of light observed on Mars and Venus were the lights of large cities. He spent years of his life trying to get funding for a giant mirror with which to signal the Martians. The mirror would be focused on the Martian desert, where the intense reflected sunlight could be used to burn figures into the Martian sand.

Around 1900, the Guzman Prize was created; the first person to establish interplanetary communication would be awarded 100,000 francs under one stipulation: Mars was excluded because Madame Guzman thought communicating with Mars would be too easy to deserve a prize.>>
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Re: APOD: A Close Pass of Saturns Moon Dione (2012 May 21)

Postby Ann » Tue May 22, 2012 4:47 am

I'm pretty sure I've read a suggestion by SETI enthusiasts that it might be possible to communicate with extraterrestrials by placing giant, planet-sized squares and pyramids in orbit around the Sun, or rather, it might be possible for super-advanced aliens to communicate with us by placing giant, planet-sized squares and pyramids in orbit around their Sun.

So if Kepler spots a really weirdly shaped planet transiting a distant star, who knows, it might be ET saying hello to us! :D

Back to today's APOD. The brightness variations between Dione and the two smaller moons is interesting. I wonder if Dione is so bright because it regularly passes close enough to Enceladus to be "snowed upon". After all, Enceladus releases tremendous jets of water vapor into space, which instantly freezes into ice crystals. If Dione regularly passes through such admittedly very attenuated cosmic "snow flurries", it might pick up a coating of snow of its own. If my hypothesis is right, then I guess that the two small moons, at least Prometheus, don't get the same helpings of Enceladus-produced snow as Dione.

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Last edited by Ann on Tue May 22, 2012 12:41 pm, edited 1 time in total.
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Re: APOD: A Close Pass of Saturns Moon Dione (2012 May 21)

Postby ta152h0 » Tue May 22, 2012 5:34 am

Hope I never suggested communicating with extraterrestials. I have enough trouble with intraterrestials.
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Marly Tower

Postby neufer » Tue May 22, 2012 11:19 am

http://en.wikipedia.org/wiki/Aerial_tel ... plications wrote:
<<An aerial telescope is a type of very-long-focal-length refracting telescope built in the second half of the 17th century that did not use a tube. Instead, the objective was mounted on a pole, tree, tower, building or other structure on a swivel ball-joint. The observer stood on the ground and held the eyepiece, which was connected to the objective by a string or connecting rod. By holding the string tight and maneuvering the eyepiece, the observer could aim the telescope at objects in the sky.

Astronomer Giovanni Domenico Cassini had the wooden Marly Tower, originally built as part of the Machine de Marly to lift water for the reservoirs and fountains at the Gardens of Versailles, moved to the grounds of the Paris Observatory. On this tower he mounted long tubed telescopes and the objectives of aerial telescopes made for him by the Italian optician Giuseppe Campani. In 1684 he used one of his aerial telescopes to find Dione and Tethys, two satellites of Saturn.

James Bradley, on December 27, 1722, measured the diameter of Venus with an aerial telescope whose objective had a focal length of 212 ft (65 m). Francesco Bianchini tried to map the surface of that same planet and deduce its rotational period in Rome in 1726 using a 2.6" (66 mm) 100 foot focal length aerial telescope.>>
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Re: APOD: A Close Pass of Saturns Moon Dione (2012 May 21)

Postby neufer » Wed May 23, 2012 9:36 pm

Click to play embedded YouTube video.
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Re: APOD: A Close Pass of Saturns Moon Dione (2012 May 21)

Postby bystander » Wed May 23, 2012 10:24 pm

I don't imagine you will dispute the fact that at present the stupid people
are in an absolutely overwhelming majority all the world over.
— Henrik Ibsen
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CICLOPS: Maps of Dione - December 2011

Postby bystander » Wed May 23, 2012 10:25 pm

Map of Dione - December 2011
Dione Polar Maps - December 2011

Credit: NASA/JPL-Caltech/Space Science Institute
Released: May 23, 2012 (CICLOPS)
I don't imagine you will dispute the fact that at present the stupid people
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