APOD: Europa and Jupiter from Voyager 1 (2017 Sep 05)

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APOD: Europa and Jupiter from Voyager 1 (2017 Sep 05)

Postby APOD Robot » Tue Sep 05, 2017 4:09 am

Image Europa and Jupiter from Voyager 1

Explanation: What are those spots on Jupiter? Largest and furthest, just right of center, is the Great Red Spot -- a huge storm system that has been raging on Jupiter possibly since Giovanni Cassini's likely notation of it 352 years ago. It is not yet known why this Great Spot is red. The spot toward the lower left is one of Jupiter's largest moons: Europa. Images from Voyager in 1979 bolster the modern hypothesis that Europa has an underground ocean and is therefore a good place to look for extraterrestrial life. But what about the dark spot on the upper right? That is a shadow of another of Jupiter's large moons: Io. Voyager 1 discovered Io to be so volcanic that no impact craters could be found. Sixteen frames from Voyager 1's flyby of Jupiter in 1979 were recently reprocessed and merged to create the featured image. Forty years ago today, Voyager 1 launched from Earth and started one of the greatest explorations of the Solar System ever.

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Re: APOD: Europa and Jupiter from Voyager 1 (2017 Sep 05)

Postby Boomer12k » Tue Sep 05, 2017 6:37 am

Oh, a Double Eclipse of Jupiter.... oh, wait... TRANSIT.... OK.... well, actually in this there should be a double eclipse of the SUN on Jupiter, from both Europa and Io... I mean there is Io's shadow, and I assume Europa's is not far behind...

Why is the red spot not so red in this...nor as big as it seems in some later images? Or am I seeing this wrong?

OH, and the "Cheshire Cat" above the shadow of Io....

Our sky's here in Salem, Oregon are sooooo smokey you could not see The Moon!!!! and it smells like a bad BARBECUE... no kidding....yuck.
Last night looked at Moon, you could see wisps of smoke going by...

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Re: APOD: Europa and Jupiter from Voyager 1 (2017 Sep 05)

Postby Ann » Tue Sep 05, 2017 7:25 am

Boomer12k wrote:Why is the red spot not so red in this...nor as big as it seems in some later images? Or am I seeing this wrong?
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Jupiter photographed by Pioneer 10 in 1973, and Jupiter in 2010(?).
Source: http://www.unmannedspaceflight.com/lofi ... t6595.html
The Great Red Spot has been steadily shrinking for many years, and certainly since https://en.wikipedia.org/wiki/Pioneer_10Pioneer visited it in 1973. But the saturation of the Great Red Spot varies, and it has been relatively red recently.

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Re: APOD: Europa and Jupiter from Voyager 1 (2017 Sep 05)

Postby neufer » Tue Sep 05, 2017 1:32 pm

Click to play embedded YouTube video.
Ann wrote:
The Great Red Spot has been steadily shrinking for many years, and certainly since https://en.wikipedia.org/wiki/Pioneer_10Pioneer visited it in 1973. But the saturation of the Great Red Spot varies, and it has been relatively red recently.


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Re: APOD: Europa and Jupiter from Voyager 1 (2017 Sep 05)

Postby Fred the Cat » Tue Sep 05, 2017 2:44 pm

Boomer12k wrote:Our sky's here in Salem, Oregon are sooooo smokey you could not see The Moon!!!! and it smells like a bad BARBECUE... no kidding....yuck.
Last night looked at Moon, you could see wisps of smoke going by...:---[===] *


Backpacking in the Seven Devils this weekend the skies went from this the day before
IMG_9287.JPG

to this last night when we returned.
IMG_9559 (2).JPG

A different type of "Great Red Spot"! :wink:
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Re: APOD: Europa and Jupiter from Voyager 1 (2017 Sep 05)

Postby Lanier » Tue Sep 05, 2017 10:58 pm

Shadow of an Eclipse on Jupiter is quite different from Earth. There is very little penumbra!
Since the sun is so far away Jupiter Eclipse must be total all of the time. Fuzziness around the shadow edge must be an atmospheric effect.

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Re: APOD: Europa and Jupiter from Voyager 1 (2017 Sep 05)

Postby geckzilla » Wed Sep 06, 2017 1:26 am

Lanier wrote:Shadow of an Eclipse on Jupiter is quite different from Earth. There is very little penumbra!
Since the sun is so far away Jupiter Eclipse must be total all of the time. Fuzziness around the shadow edge must be an atmospheric effect.

I think the fuzziness is a narrow penumbra. The Sun may be relatively small compared to Europa from Jupiter's viewpoint, but it's still got an angular diameter that occupies a significant fraction of Europa's angular diameter. Around 6 arcminutes for the Sun and around 16 arcminutes for Europa. (Europa may be slightly larger from Jupiter's surface; I'm not sure if Solar System Simulator's measurement is from the surface or center of Jupiter.)
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Re: APOD: Europa and Jupiter from Voyager 1 (2017 Sep 05)

Postby neufer » Wed Sep 06, 2017 2:05 am

geckzilla wrote:
Lanier wrote:
Shadow of an Eclipse on Jupiter is quite different from Earth. There is very little penumbra!
Since the sun is so far away Jupiter Eclipse must be total all of the time. Fuzziness around the shadow edge must be an atmospheric effect.

I think the fuzziness is a narrow penumbra. The Sun may be relatively small compared to Europa from Jupiter's viewpoint, but it's still got an angular diameter that occupies a significant fraction of Europa's angular diameter. Around 6 arcminutes for the Sun and around 16 arcminutes for Europa. (Europa may be slightly larger from Jupiter's surface; I'm not sure if Solar System Simulator's measurement is from the surface or center of Jupiter.)

The shadow is Io's: Around 6 arcminutes for the Sun and around 32 arcminutes for Io.
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Re: APOD: Europa and Jupiter from Voyager 1 (2017 Sep 05)

Postby geckzilla » Wed Sep 06, 2017 2:17 am

neufer wrote:
geckzilla wrote:
Lanier wrote:
Shadow of an Eclipse on Jupiter is quite different from Earth. There is very little penumbra!
Since the sun is so far away Jupiter Eclipse must be total all of the time. Fuzziness around the shadow edge must be an atmospheric effect.

I think the fuzziness is a narrow penumbra. The Sun may be relatively small compared to Europa from Jupiter's viewpoint, but it's still got an angular diameter that occupies a significant fraction of Europa's angular diameter. Around 6 arcminutes for the Sun and around 16 arcminutes for Europa. (Europa may be slightly larger from Jupiter's surface; I'm not sure if Solar System Simulator's measurement is from the surface or center of Jupiter.)

The shadow is Io's: Around 6 arcminutes for the Sun and around 32 arcminutes for Io.

Thanks. Still enough for a soft shadow edge, right? A 3/16th instead of 3/8th ratio.
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