# Tag Info

### 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 ...
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### What are the orbital velocities of the other planets? For objects in a 'Low-Earth-Orbit' around planets other than Earth, e.g.?

The formula for orbital velocity is $\sqrt{GM/r}$ and for a "low" orbit you would mean orbit at, or close to the surface, ie with a radius equal to the radius of the planet. This makes ...
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### At what point in history was the idea of planets being spit out by the sun abandoned?

That specific idea doesn't seem familiar to me, and I work in that field. Particularly this idea would only be called 'theory' when making testable predictions. The only thing that comes to mind here ...

### How scientists find the direction of rotation of planets?

I'll focus first on the question of the title: "how do we find / measure rotation?" The easiest method is the same as everyone else: look and see. Take images some time apart and you will ...
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Accepted

### At what point in history was the idea of planets being spit out by the sun abandoned?

Between 1965 and 1980 I recall a book from the "Ladybird" series of short non-fiction books for children which included two possibilities for the formation of the planets. One was "...
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### Which JWST instrument modes are compatible with observations of the bright trans-Earth planets Mars, Jupiter, and Saturn? Which aren't?

There are approved proposals for Cycle 1 to point the JWST at The Jovian system Jupiter's great red spot Mars Saturn and its moons and rings In those PDFs, they describe exactly what instruments ...

### What is k2, how does it relate to Io's volcanism and how can Juno constrain its value?

It is called Tidal love number. The definition is as follows: In Newtonian gravitational theory, a tidal Love number relates the mass multipole moment created by tidal forces on a spherical body to ...
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### At what point in history was the idea of planets being spit out by the sun abandoned?

Spit out? In 1955 my parents gave me an illustrated book on Astronomy, which gave two hypotheses: the Kant-Laplace (nebular) hypothesis, and Sir James Jeans' idea that a passing star pulled some ...
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### Which JWST instrument modes are compatible with observations of the bright trans-Earth planets Mars, Jupiter, and Saturn? Which aren't?

All modes can be used. But for bright targets, observations are limited to specific filters, subarrays, regions of the target planet, or spectral intervals. James Norwood and colleagues wrote a paper ...
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### What are the orbital velocities of the other planets? For objects in a 'Low-Earth-Orbit' around planets other than Earth, e.g.?

"Low-Earth-Orbit" is kind of arbitrarily defined, and I don't believe there's a widely accepted general definition of a low orbit that can be applied to other planets. If you know what the ...
Accepted

### What is k2, how does it relate to Io's volcanism and how can Juno constrain its value?

$k_2$ is one of three tidal Love-Shida numbers related to how gravitation of another body (Jupiter in this case) changes a planet-like body's second degree spherical harmonics (Io in this case). Three ...
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### How does the Hubble Space Telescope measure the speed of the wind inside Jupiter's Great Red Spot?

There's nothing special happening to determine the velocity: Several pictures are taken, e.g. each Jovian day and the distance some features in the clouds have moved is calculated. For that, image ...
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