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cjackson
2011-Oct-08, 09:01 PM
How large would Jupiter appear from the surface of Ganymede? Also, how large would Neptune appear from Triton's surface?

captain salty
2011-Oct-08, 09:44 PM
Jupiter has a angular size of roughly 7.7 degrees from Ganymede.
Neptune is 8 degrees as seen from Triton.

cjackson
2011-Oct-09, 02:17 AM
So I gather they would appear quite large in the sky?

DonM435
2011-Oct-09, 02:24 AM
Earth's moon is seen as just half a degree, so those would appear 15 or 16 times as wide.

Middenrat
2011-Oct-09, 03:09 AM
The vista would be giddying. There you are on Ganymede, itself larger than Mercury, looking at a fair distant horizon, but there's a whacking great gas giant hanging there in the sky: it would totally confuse my Up from Down sense. Wish I could book a trip...

croatix
2011-Oct-09, 02:09 PM
How large would Jupiter appear from the surface of Ganymede? Also, how large would Neptune appear from Triton's surface?

You can check it using Stellarium (http://www.stellarium.org/). When started, press F6 to change your location. In new window, by Planet choose any desired object, in this case Ganymede or Triton. Then pick some point on Minimap. Try picking various points until you find some good enough to well see Jupiter od Neptune, and then the show can start!

Cheers :)

WayneFrancis
2011-Oct-10, 12:04 AM
How large would Jupiter appear from the surface of Ganymede? Also, how large would Neptune appear from Triton's surface?
About a half a foot. Good approximation is about 1 inch per 1 degree across the sky at about arms length. Most people don't think that your thumb tip held at arms length will cover the moon. (make sure you close one eye) :)

frankuitaalst
2011-Oct-10, 05:03 PM
The gif hereunder is the result of a simulation I've run .
The viewpoint first is Earth , looking at the moon . In the second picture moon looking at Earth .
The last picture represents what an observer in the center of Ganymede would see looking at Jupiter .
The view angle is kept consatnt at 60° wide
15469

Romanus
2011-Oct-11, 12:26 AM
It would be big, but not astoundingly so; your closed fist could easily cover Jupiter's disk at arm's length.

WayneFrancis
2011-Oct-11, 12:57 AM
It would be big, but not astoundingly so; your closed fist could easily cover Jupiter's disk at arm's length.

Romanus
2011-Oct-11, 01:26 AM
A closed fist at arm's length is about 10 degrees.

http://brahms.phy.vanderbilt.edu/a103/info/angdist.shtml

2011-Oct-11, 09:24 PM
What does Saturn look like from the surface of Titan?

crosscountry
2011-Oct-11, 11:25 PM
http://i28.photobucket.com/albums/c249/ccountry/th_Screenshot2011-10-11at62225PM.png (http://s28.photobucket.com/albums/c249/ccountry/?action=view&current=Screenshot2011-10-11at62225PM.png)

Neptune from Triton
http://i28.photobucket.com/albums/c249/ccountry/th_Screenshot2011-10-11at62023PM.png (http://s28.photobucket.com/albums/c249/ccountry/?action=view&current=Screenshot2011-10-11at62023PM.png)

Jupiter from Ganymede
http://i28.photobucket.com/albums/c249/ccountry/th_Screenshot2011-10-11at61834PM.png (http://s28.photobucket.com/albums/c249/ccountry/?action=view&current=Screenshot2011-10-11at61834PM.png)

Although Starry night doesn't always represent angular dimensions accurately.

EDG
2011-Oct-12, 08:58 PM
What does Saturn look like from the surface of Titan?

It probably wouldn't be visible from the surface of Titan, given the cloud cover on the satellite.

ozark1
2011-Oct-18, 10:49 AM
Jupiter isn't visible from half of Ganymede due to tidal locking. Same for Triton and Neptune.

agingjb
2011-Oct-18, 11:01 AM
It probably wouldn't be visible from the surface of Titan, given the cloud cover on the satellite.

Yes, sadly the classic Chesley Bonestell painting isn't realistic for Saturn from Titan. Many of the other paintings are fairly close to what might be seen though.

crosscountry
2011-Oct-20, 03:54 AM
Jupiter isn't visible from half of Ganymede due to tidal locking. Same for Triton and Neptune.

I didn't believe that about Ganymede and Jupiter until I checked it out myself. How bizarre, especially since there is a resonance with Io and Europa. Thanks for pointing that out.

Hornblower
2011-Oct-20, 11:24 AM
I didn't believe that about Ganymede and Jupiter until I checked it out myself. How bizarre, especially since there is a resonance with Io and Europa. Thanks for pointing that out.

I do not see anything bizarre about the locking. The orbits are nearly circular, and the tides raised by Jupiter are so strong that the moons have been locked since very early in their history.

crosscountry
2011-Oct-20, 11:12 PM
I do not see anything bizarre about the locking. The orbits are nearly circular, and the tides raised by Jupiter are so strong that the moons have been locked since very early in their history.

If Ganymede was the only object in the system, sure, just like the Earth-Moon system. It also has a resonance with Io and Europa, that I had kind of figured would keep it from becoming tidally locked.

Hornblower
2011-Oct-21, 01:31 AM
If Ganymede was the only object in the system, sure, just like the Earth-Moon system. It also has a resonance with Io and Europa, that I had kind of figured would keep it from becoming tidally locked.

They keep their orbits synchronized with their mutual perturbations, but the tides they raise on each other are very slight compared to what Jupiter raises on them. Those components of tidal action should not be enough to break the lock imposed by Jupiter. I would not expect anything more than small librations about the mean locked orientations, along with the heat generated in Io by these perturbations.