56
votes
Accepted
Why does the Sun have different day lengths, but not the gas giants?
It's a matter of how "day" is defined.
Wikipedia's article on Jupiter cites this IAU/IAG paper for the length of a Jupiter day. In it, footnote (e) of table I has the following:
The equations for ...
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33
votes
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Why can't stars be multicolored like gas giants?
Just rotation is the wrong tree to bark up on.
You see color variations on gas giants due to differences in composition, i.e. ammonia vs. sulfuric acid clouds on Jupiter, which are transported ...
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30
votes
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Where do we define the "surface" of a gas planet?
There are two common definitions in use for the surface of gas planets:
The 1-bar surface: As pressure increases, the deeper in we go into the gas planet, we will hit a pressure of 1 bar at some ...
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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 $...
- 156k
19
votes
Accepted
Is there a gas giant orbiting TRAPPIST-1?
No such planet has been announced as having been discovered. The paper only shows evidence for the 7 (really 6 because the 7th can't be officially confirmed with only 1 observation) terrestrial ...
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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 ...
- 126k
13
votes
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Why don't we have in-between planets?
Super-Earths and Mini-Neptunes are the "in-between" types of exoplanets you're looking for. A sweeping generalization would put most in the range of $\sim1$-$10M_{\oplus}$ (Earth masses), with some ...
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13
votes
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Why does each and every planet of our solar system have an unique axial tilt angle?
In the early stages of the formation of the solar system, planetesimals start condensing and everything rotates with angular momentum inherited from the collapsing cloud of gas and dust, so the ...
- 15k
10
votes
How can clouds form in Jupiter's atmosphere of Hydrogen and Helium?
First, it's a great question. Mostly the answer is straight forward, so I can answer it, but it's still a great question.
and I'll add a similar, but slightly more detailed picture to the one you ...
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10
votes
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Why is the core of a gas giant supported by electron degeneracy pressure instead of nuclear fusion?
The test to see whether degeneracy pressure is going to be significant is to compare $kT$ with the Fermi energy $E_F$
The Fermi energy is the energy level up to which all energy states would be ...
- 156k
9
votes
Can a gas giant be hollow?
Newton's shell theorem proves that inside a gas giant, any layers that are further than you from the centre have a zero gravitational effect on you. So if you are inside a gas giant (and by some magic ...
- 126k
8
votes
Accepted
Why do Uranus and Neptune have more methane than Jupiter and Saturn?
Why does Uranus and Neptune have more methane than Jupiter and Saturn?
It's a combination of equations of state (EOS), serpentinization, and mixing (rotational and convective) that favors a ...
- 2,676
8
votes
Fate of Jupiter when our sun dies
How will the atmosphere deal with the extreme heat?
Using this article as a guide
During most of the red giant lifetime, the sun will be only 30 times
brighter than its current state. Toward the ...
- 24.1k
8
votes
Accepted
Why do the solar system planets go rock-gas-ice instead of rock-ice-gas when moving away from the sun?
Prelude
It is now generally accepted in the planet formation community that planets form as a side-product of the star formation process in so-called protoplanetary discs.
Protoplanetary discs have ...
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8
votes
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Gravity of a gaseous planet without a core
The gravitational force on a small mass on the outside of a planet is always the Newtonian $$F_{G}=-\frac{GM}{r^2},$$ so any planet, and particularly, any mass in the universe produces a gravitational ...
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7
votes
Why does each and every planet of our solar system have an unique axial tilt angle?
You could also ask:
Why is each planet a different size.
or
Why is each planet a different colour.
or even
Why are the apples in my fruit bowl pointing in different directions.
The reason ...
- 126k
7
votes
Can a dying, swelling, star be rejuvinated by enveloping orbiting gas giants?
Stars turn into Red Giants not because they're running out of fuel, but because they're accumulating material they can't use for fusion (yet) in the core. The star isn't so much dying of starvation as ...
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7
votes
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What's the critical mass of a rocky planet before its gravity traps enough gas in its atmosphere to start becoming a gassy planet
In most planet formation theories, the boundary is around 10 Earth masses - the build up of the core mass before that is relatively slow, but once it crosses that threshold, the planet gains mass ...
- 4,894
6
votes
What would happen to a gas planet if its core mass goes beyond the Chandrasekhar limit?
Gas giants like Jupiter consists mainly of Hydrogen and some Helium. If you gradually add mass to these planets then core temperatures will rise gradually and a stage will come where they will ignite ...
- 528
6
votes
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Is carbon dioxide gas giants possible?
While not absolutely impossible this is not a likely situation. The reason is that for a planet to be a "giant", then it will have enough gravity to hold on to its hydrogen and helium. Conversely, if ...
- 126k
6
votes
Why don't we have in-between planets?
This is not a characteristic of the solar system. It is a characteristic of the definitions of the names you used. Neptune and Uranus are the bodies you believe to be missing. In fact, with the mass ...
- 459
6
votes
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Are gas giants supported by thermal pressure?
I am not sure what you mean by "thermal" pressure. Jupiter is supported by pressure, just like all objects that are in (approximate) hydrostatic equilibrium.
That pressure is provided by your ...
- 156k
6
votes
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Gas giants and seismology
I'm certainly not an expert, but from what I understand, the type of observation done in helioseismology might not work with gas giants, hot jupiters, ice giants, etc.
The sun is dense enough and it ...
- 24.1k
6
votes
Accepted
Is there any planet out there which is half gaseous and half rocky ? is this possible?
Probably. Relatively little is known about exoplanets because they're very hard to get a good look at, but there's no reason why a rocky world couldn't accumulate enough ices and/or gas to also ...
- 24.1k
6
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Largest non-hot gas giants
According to the models of Mordasini et al. 2012 it is about 13 Earth radii (about 1.2 Jupiter radii) for gas giants older than a billion years.
Younger gas giants that are still contracting ...
- 156k
6
votes
Are gas giants actually rare?
There is an observational bias and it is taken into account when you see inferences about planet frequency.
The methods to find planets are inherently biased towards finding large, close-in planets. ...
- 156k
6
votes
Why can't stars be multicolored like gas giants?
The atoms in stars have disassociated electrons at random distances, they are ionised, and the energy converted to light is at a continuous spectrum of wavelegnths and colors.
The heaviest elements ...
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