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74 votes
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Why can't we see Saturn's phases from earth?

Phases are just different perceived illuminations of an object at different illumination and observing angles. If the observer is, with respect to the object, located in a similar direction as the ...
Swike's user avatar
  • 3,896
57 votes

Why can't we see Saturn's phases from earth?

All the other answers here are complete, and more in-depth than anything I would write. However, if you prefer to look at things visually, here is a terrible not-to-scale 2 minute paint drawing. No ...
Azrantha's user avatar
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49 votes
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How large can a ball of water be without fusion starting?

You really need a full-blown stellar evolution model to answer this precisely and I'm not sure anyone would ever have done this with an oxygen-dominated star. To zeroth order the answer will be the ...
ProfRob's user avatar
  • 149k
44 votes

Why is there a mountain inside the Herschel crater on Mimas?

In the extreme energy of a large impact, the rock behaves like a liquid (It isn't actually completely melted, though some is. The extreme forces cause the rock to flow). As the impactor hits the moon, ...
James K's user avatar
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41 votes
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What does the Earth look like when viewed from Saturn?

Yes! It's a tiny blue dot of just about 1.6 arc seconds diameter. Cassini made the most famous image of the "In Saturn's Shadow – The Pale Blue Dot", in remembrance of the first such image ...
planetmaker's user avatar
31 votes
Accepted

How is it possible that Saturn's gravitational acceleration felt by Mimas is stronger than Mimas' own surface gravity?

An object on Mimas' surface would be much more attracted to Saturn than it is to Mimas. You are missing that Mimas as a whole accelerates gravitationally toward Saturn. What this means is that a ...
David Hammen's user avatar
  • 33.7k
30 votes

Help understanding this unsettling image of Titan, Epimetheus, and Saturn's rings?

This NASA page says this photo was taken on April 28 2006. Using Celestia, I managed to find the picture from Cassini that best lines up with the photo. It doesn't match up precisely, but that's to ...
Ingolifs's user avatar
  • 4,157
30 votes
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What do Saturn's rings look like during a total solar eclipse, viewed from one of its moons?

Cassini (the orbiter) has captured images of Saturn with the sun in eclipse: The rings are back-lit, They self-shadow quite well but not enough to completely block sunlight, so appear bright against ...
James K's user avatar
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24 votes
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How did Arecibo detect methane lakes on Titan, and image Saturn's rings?

Titan "lakes": Published Open Access in Science: Radar Evidence for Liquid Surfaces on Titan Campbell, D. B., Black, G. J., Carter, L. M., and Ostro, S. J., Science 302, 5644, pp. 431-434, 17 Oct ...
uhoh's user avatar
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23 votes
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Which Saturn satellite passes closest to Saturn's rings and at what distance?

Pan, Daphnis, and various other moonlets, I would argue, are inside the rings. If you explicitly discount the Encke gap (which Pan orbits in) and the Keeler gap (which Daphnis orbits in) as being ...
Ingolifs's user avatar
  • 4,157
18 votes
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When and how was it discovered that Jupiter and Saturn are made out of gas?

I'm unsure of the "history of science" aspect of this, but an actual deduction that these are gas giants would require Kepler's laws and Newton's law of gravity combined with a modest ...
ProfRob's user avatar
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17 votes
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Are there other pictures of Titan surface from Huygens?

One second of googling reveals the whole archive: http://esamultimedia.esa.int/docs/titanraw/index.htm (note you can click onto the strips to inspect them!) The archive depicts the whole decent of ...
AtmosphericPrisonEscape's user avatar
17 votes
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Why is Enceladus's albedo greater than 1?

To answer this, one really has to understand how the geometric and bond albedos are defined. Let's start with the bond albedo since its simpler. Bond Albedo The Bond Albedo is just the fraction of ...
zephyr's user avatar
  • 15k
17 votes
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Planets looks like normal stars when I see them using telescope

I'm a VERY amateur observer myself and my telescope has the exact same aperture as yours. I can all but guarantee that you should definitely be able to see Saturn rings and Jupiter moons (and even ...
GoldSkulltulaHUnter's user avatar
17 votes

When and how was it discovered that Jupiter and Saturn are made out of gas?

By 1690, Giovanni Cassini was able to estimate the rotation period of the planet and noticed that the atmosphere of Jupiter undergoes differential rotation which confirmed that Jupiter was made of gas ...
Nilay Ghosh's user avatar
  • 4,436
14 votes

Hypothetically, would we be able to see the moon from Saturn's North Pole?

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 ...
Mark Olson's user avatar
  • 7,620
13 votes

Why can't we see Saturn's phases from earth?

The answer is simple geometry: we are 1 AU from the Sun, Saturn is 10x further from the Sun. Looked at Earth from Saturn, Earth is always in front, behind or immediately next to the sun; an observer ...
planetmaker's user avatar
13 votes
Accepted

What is this 877-year cycle in the orbits of Jupiter & Saturn, and this multimillion-year cycle in the lunar orbit?

A biography of Laplace mentions his derivation of an 877 year cycle in the motions of Saturn and Jupiter. The periods of the planets are about 30 and 12 years respectively so they will approximately ...
James K's user avatar
  • 119k
13 votes

Planets looks like normal stars when I see them using telescope

With f=900 mm and a 25 and 10 mm eyepieces you would be viewing at 36x and 72x. 36x is a very reasonable magnification under any condition, and 72x can probably still be considered "useful ...
uhoh's user avatar
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12 votes
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Hypothetically, would we be able to see the moon from Saturn's North Pole?

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 ...
Mike G's user avatar
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12 votes
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Help understanding this unsettling image of Titan, Epimetheus, and Saturn's rings?

The JPL Solar System Simulator doesn't show Epimetheus but does show Titan behind the Encke gap at 2006-04-28 08:12 UTC. The simulated surface texture is probably composed of VIMS images in infrared ...
Mike G's user avatar
  • 18.6k
12 votes

How did Arecibo detect methane lakes on Titan, and image Saturn's rings?

It did not detect methane lakes. It found that Titan was shiny (in radar terms): that is, the reflections were from a smooth surface rather than a rough one, and at the same time not very intense. ...
Martin Kochanski's user avatar
12 votes
Accepted

Are the Jupiter-Saturn conjunctions and winter solstice related?

Not in any way, no. The December solstice is the moment when the Sun reaches its southernmost point in its daily path in the sky (the June solstice, when the Sun reaches its northernmost point). It ...
Pierre Paquette's user avatar
11 votes
Accepted

What are the periods of Saturn's rings?

Hours to days. The orbital period is proportional to the 3/2 power of the orbital radius, and the orbital period of the moon Methone (and thus of the particles in its associated ring arc) is very ...
Russell Borogove's user avatar
10 votes
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Size of Saturn's ring material

The vast majority of the particles in Saturn's rings are small, on the order of $\sim10^{-1}$ m or lower. The columnar number density, according to data from Voyager 1 and Earth-based observations, ...
HDE 226868's user avatar
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10 votes
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How is a day measured on a gas giant?

That the rotation period of the bulk mass of a planet is estimated through something with the magnetic field is true. But let me maybe elaborate a bit in-depth on that. No planetary magnetic field ...
AtmosphericPrisonEscape's user avatar
10 votes
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Why has Saturn stopped contracting gravitationally?

The rate at which a planet contracts is determined by how much heat it can radiate from its surface and how close it is to the minimum radius allowed by electron degeneracy pressure (which is ...
ProfRob's user avatar
  • 149k
10 votes

How to measure mass of planets' core from orbit

I certainly don't know the details of these kinds of calculations, but as my thought is a bit too long for a comment I'll write it up as an answer. If you measure the flattening of a planet due to ...
theWrongAlice's user avatar
9 votes
Accepted

Is there, in fact, any close-up photography of Saturn's rings, showing individual pebbles/rocks?

The rings are about 3% solid in the densest parts, but this translates to a separation between 30cm particles of about 1metre. There are no images Because approaching the dense part of the rings would ...
James K's user avatar
  • 119k
9 votes

Trying to understand the way Saturn's ring look in this famous Cassini image

What's going on with the distortion of the rings on the upper half when they (presumably) cross in front of Saturn? The brownish areas you see on Saturn are ring light, analogous to seeing the Earth ...
David Hammen's user avatar
  • 33.7k

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