Hypothetically speaking, if Saturn had a solid surface that we could stand on, would we be able to see our Moon from the North Pole of Saturn? Would the rings of Saturn obstruct the view?
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4 Answers
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First of all, at that distance seeing the Moon and seeing the Earth amounts to the same thing. At its closest, Saturn is around 3000 times as far from Earth as the Moon is, so viewed from Saturn, the Moon is never more than about a minute of arc away from the Earth.
If you can see Earth from the North Pole of Saturn, you can see the Moon, also. (Though it would be a lot dimmer.)
But if you can See the Earth from Saturn's pole, then you can also see Saturn's pole from Earth. So your question can equally well be phrased as "Can Saturn's north pole be seen from Earth and if so, when?"
If you look at pictures of Saturn from Earth, the rings are sometimes tilted so far that they cover one polar region, though it's also true at those times that polar region tilted away from Earth, anyway! Most of the time the rings are either not tilted enough to cover the poles or tilted to cover the south pole.
So the answer is that during most of Saturn's orbit around the Sun, the rings would not obscure the sightline from Saturn's north pole to the Moon.
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1$\begingroup$ As far as I can tell, the rings would never obscure the sightline from Saturn's north pole to the Moon. Saturn's body will block the view half of the time, though. $\endgroup$ Commented May 29, 2018 at 9:03
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$\begingroup$ That could be. All I can tell is that there are times when both the rings and the bulk of the planet interfere. I can't tell for sure if there are times only one does (or which). $\endgroup$ Commented May 29, 2018 at 11:37
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1$\begingroup$ The only possible way to see both poles is when Saturn isn't tilted as seen from the Earth. If it appears tilted and we can see a pole, it means the other pole is hidden by Saturn's body. It is too late for the rings to interfere. $\endgroup$ Commented May 29, 2018 at 12:11
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1$\begingroup$ I make no assertions about seeing both poles simultaneously! But I see your point about the geometry that even if the rings were infinite in extent, as long as they're in the equatorial plane and Saturn is symmetric around its axis, they are never visible from the north pole. $\endgroup$ Commented May 29, 2018 at 12:23
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$\begingroup$ Your last explanation is clearer. $\endgroup$ Commented May 29, 2018 at 13:38
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Yes, if you observe Earth and the Moon at a favorable time. Near a Saturn summer solstice, e.g. between 2012 and 2022, Earth appears well above the horizon from Saturn's north pole. If the planet body is out of the way, so are the rings.
The other observability issue is Earth's elongation from the Sun. This reaches a maximum of about 6$^\circ$ at intervals of about 189 days, e.g. late September 2018 or early April 2019. Even then, you would need to shade your optics from the Sun and be above Saturn's atmosphere.
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For these kind of questions, you might want to use Stellarium, a free open source planetarium.
You can specify the location of the observer on many celestial bodies, including Saturn.
Any time between 2011 and 2023
- With this tool, you can see that the moon will be in the northern saturnian sky non-stop between 2011 and 2023.
- You can also see that the moon will have an apparent magnitude of $5$ when full.
- The sun has a magnitude of approximately $-20$ as seen from Saturn. It is $10^{10}$ times brighter than the full moon!
- Saturn is an outer planet, so Earth and Luna can never be in opposition as seen from Saturn.
During a Titan transit
What we call a Titan transit is basically a solar eclipse for Saturnians. During this time, it should be much easier to observe Luna from Saturn.
2nd November 2038
On the 2nd of November 2038 at 15:45 UTC, a Titan transit will occur in the northern hemisphere. Luna will be almost full as seen from Saturn.
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1$\begingroup$ In the English language, "Luna" is not a thing. The name of the Moon is, quite simply, "the Moon." $\endgroup$– corsiKaCommented May 28, 2018 at 18:36
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$\begingroup$ @corsiKa: Thanks. I just used it to avoid the confusion with Titan, a moon of Saturn. I'll investigate and edit my answer if necessary. $\endgroup$ Commented May 28, 2018 at 18:44
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4$\begingroup$ @corsiKa "Occasionally, the name "Luna" is used. In literature, especially science fiction, "Luna" is used to distinguish it from other moons, while in poetry, the name has been used to denote personification of our moon." en.wikipedia.org/wiki/Moon $\endgroup$ Commented May 29, 2018 at 3:50
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$\begingroup$ @Acccumulation Sure, some artsy fartsy types take poetic license in their writing. In Science, there is a body of people who determine the proper terms to avoid confusion, they decided to call it "the Moon". $\endgroup$– corsiKaCommented May 29, 2018 at 14:11
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Depends on whether you mean "unobstructed line of sight" or "can actually make out with the naked eye". The other answers have answered the first question, but I think it's worth pointing out the human eye has a resolution of about 10^-4 radians. Saturn is about 1.2 x 10^12 meters away, which means that the moon is about 1.2 x 10^12 meters away from Saturn. The diameter of the moon is about 3.4 x 10^6 m, so the moon is about 3 x 10^5 moon diameters away from Saturn. We can therefore approximate the apparent size of the moon as 1/(3 x 10^5), or 3 x 10^-6, radians, making it about 1/30 the size necessary to be seen from Saturn. Which is not as large of a margin as I thought, so I'm wondering whether there's an error somewhere.
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1$\begingroup$ The order of magnitude seems correct. In the first screenshot of my answer, you can see that the apparent diameter is half an arcsecond. It is definitely too small to be seen with the naked eye from Saturn. What's more important though is that the sun will be always close to the moon as seen from Saturn, and the sun is 10 billion times brighter. $\endgroup$ Commented May 29, 2018 at 10:20