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73 votes

Why do Jupiter’s moons have so much water?

tl;dr: They have more water because they captured it as ice, and it’s easier to hold onto ice than water vapor. Planets (and by extension, moons) beyond the frost line were formed with ice as a part ...
Justin T's user avatar
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60 votes
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Why isn't the asteroid belt affected by Jupiter's gravitational field?

The asteroid belt is affected by Jupiter's gravity. There are stable orbits inside of Jupiter's orbit. Jupiter's Hill Sphere has a radius of 53 million km. If you are more than 53 million km from ...
James K's user avatar
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48 votes
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Why don't the inner moons of Jupiter have tidally-induced volcanism?

It’s because they are much smaller than Io. Tidal forces are differential forces, that is, they result from the difference in gravitational pull on one side of a body compared to the other. When an ...
Eric Jensen's user avatar
  • 4,894
39 votes

Is Jupiter a failed star?

No. Besides the 13 Jupiter-masses required to ignite deuterium burning, and make Jupiter into a Brown Dwarf, there is a clear difference between the formation pathways of Brown Dwarves and Gas ...
AtmosphericPrisonEscape's user avatar
36 votes

Is Jupiter's Red Spot "locked in place" or does it move around?

It does drift relative to other parts of the atmosphere. The lack of a surface makes defining the actual rotation period of Jupiter rather difficult. The currently accepted value of 9h:55m:29.7s is ...
James K's user avatar
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33 votes
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Why doesn't the Sun wobble towards Jupiter instead of away from Jupiter?

The part of your intuition that is correct is that Jupiter pulls the Sun towards it. The problem is that "pulls towards" does not mean "brings closer"! The gravitational force ...
nanoman's user avatar
  • 677
31 votes

Why can't our Sun be a binary with Jupiter as a T or Y dwarf?

But why can't Jupiter be a Y Dwarf who is in the binary relationship with the Sun? There are two reasons: One is that Jupiter is too small to have ever undergone fusion of any sort. To qualify as a ...
David Hammen's user avatar
  • 34.1k
31 votes
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Why does the solar analemma have a strange shape on Jupiter?

As written on Wikipedia page about this: On Earth, the analemma appears as a figure-eight, but on other Solar System bodies, it may be very different due to the interplay between the three parameters ...
User123's user avatar
  • 2,879
29 votes
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Why do gas giants have clearly delineated surfaces, whereas the Earth's atmosphere fades into space?

In an isothermal atmosphere, the exponential scale height of the atmosphere is $$ h \sim \frac{k_\mathrm B T}{\mu g},$$ where $g$ is the gravitational field, $\mu$ is the mean mass of a particle and $...
ProfRob's user avatar
  • 155k
24 votes
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Is there any orbit at which the Roche limit can be "felt"?

Roche limit happens where the gravity of the object, trying to pull the object together, becomes smaller than the tidal force (trying to pull the object apart). But the astronaut is bound by not ...
peterh's user avatar
  • 3,179
22 votes
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During solar eclipses on Jupiter, can the moon(s)' shadow(s) on the surface be seen from Earth with a telescope?

Yes, you can see it (I have seen Io's shadow on Jupiter and we were happy it was visitor night so that we could share the view with guests) A 50cm mirror and 125x magnification allows you to see it ...
planetmaker's user avatar
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22 votes

Why was Jupiter so bright; is it the "phase"?

tl;dr: There's about a 1.4 mag oscillation due to $1/r^2$ effects and only a very tiny residual due to illumination angle. I went to JPL's Horizons and extracted the distances between Jupiter and the ...
uhoh's user avatar
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20 votes
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Did we discover 10 or 12 new moons of Jupiter?

Per the Carnegie Science article that Magic Octopus Urn linked from NASA in the comments, a Carnegie Science team led by Scott S. Sheppard noticed something new in spring of 2017 (though some ...
called2voyage's user avatar
  • 6,300
20 votes
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Is it possible to see Callisto with the naked eye when it's at its greatest elongation from Jupiter?

This has been an area of controversy for quite some time now, with no clear resolution (if you'll pardon the pun). There's been interest in supporting or refuting claims that observers were able to ...
HDE 226868's user avatar
  • 37.3k
20 votes

Is Jupiter's Red Spot "locked in place" or does it move around?

Yes, as with all other storms, the Great Red Spot is dynamic, so it constantly changes its size and shape and it shifts and drifts and is not just "locked in a definite position". According ...
Nilay Ghosh's user avatar
  • 4,733
19 votes
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How often are there lunar eclipses on Jupiter

Every Galilean moon and inner moon go into lunar eclipse once per orbit. How often is there a lunar eclipse of the Jovian moons? I set up a little animation of the Galilean moons (I didn't include ...
Ingolifs's user avatar
  • 4,155
19 votes
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What is behind the Great Red Spot's longevity?

Standard answers, as found here, (partial quote) Unlike Jupiter, the Earth has land masses that cause major storms to lose energy due to friction with a solid surface. Without this feature, Jupiter’...
Carl Witthoft's user avatar
19 votes

Is Jupiter warming the Earth? (Earth, Sun Jupiter system)

If you want to model the entire solar system, it's best to model the Sun, the planets, the asteroids, etc. with respect to the barycenter. That choice reduces the equations of motion to their ...
David Hammen's user avatar
  • 34.1k
19 votes
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What are the black spots/blobs in JWST Jupiter's images?

The black blob comes from a region of dead pixels on one of the NIRCam detectors, A1 (as someone on Reddit correctly identified). STScI has a display of flat field images for a number of segments; a ...
HDE 226868's user avatar
  • 37.3k
18 votes
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Fate of Jupiter when our sun dies

Jupiter won't evolve into a star, it is not big enough. A body would have to have about 80 times the mass of Jupiter for there to be significant fusion occurring in the core. The end of life of the ...
James K's user avatar
  • 125k
18 votes
Accepted

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
  • 155k
18 votes
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Why was Jupiter so bright; is it the "phase"?

Jupiter appears particularly bright because it is close to Earth at the moment, it is also high in the sky (in the Northern Hemisphere). However its brightness doesn't vary that much. Jupiter reached ...
James K's user avatar
  • 125k
17 votes

Why don't the inner moons of Jupiter have tidally-induced volcanism?

There are four moons that are closer to Jupiter than Io with higher eccentricities, yet they don't seem to have any volcanism at their surface. Only one of those innermost moons (Thebe) has an ...
David Hammen's user avatar
  • 34.1k
17 votes

Jupiter with a mobile phone and Celestron Astro FI 102mm Maksutov

Congratulations on your purchase. The first pictures dont' show anything much. Just a out-of-focus blur. The last one shows Jupiter and three of its moons. I've overlaid the image onto a simulated ...
James K's user avatar
  • 125k
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
  • 4,733
15 votes

How often are there lunar eclipses on Jupiter

The orbits of the Galilean satellites have a roughly 2° incline. Based on their distance from Jupiter and on the radius of Jupiter, I computed the apparent diameter of Jupiter from these satellites. ...
usernumber's user avatar
  • 17.6k
15 votes

Is Jupiter a failed star?

Short answer: no It all of course depends on how you define the term failed star. In general, a star should be able to generate heat by fusing atoms together, and it requires about 13 times the mass ...
tuomas's user avatar
  • 1,837
15 votes
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Why does Callisto only have eclipses every 3 years?

They do happen at certain points of every Jovian year. Jupiter's orbital period is approximately 12 Earth Years. the relative angle between the plane of Callisto's orbit and the plane of Jupiter's ...
notovny's user avatar
  • 4,786

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