When the sun becomes a black dwarf

[Dremmer]

Will the gas planets become solid? Since they are no longer receiving heat from the Sun?

 

[fillipeano]

Black Dwarfs are still hypothetical, but I would think the gas planets would turn to ice. Since the sun would lose mass in its white dwarf stage, the orbits of the planets, due to gravity, will change.

 

[FtlIsAwesome]

I don't think the gas giants will become solid due to lack of light and heat. They'd probably stay the same as they are now.

 

[redwood973]

Juipiter actually gives off more energy than it receives from the sun. I'm not sure about the other jovians.

 

[TheTechNoir]

Juipiter actually gives off more energy than it receives from the sun. I'm not sure about the other jovians.

Would that really continue to be the case this incredibly far into the future though? I don't mean for that to come out sounding like I am doubtful, much less saying you are wrong, genuine question as I have no idea whatsover but it seems very reasonable too to think that it wouldn't continue doing so for that long.

 

[pergradus]

Juipiter actually gives off more energy than it receives from the sun. I'm not sure about the other jovians.

ugh... Jovian refers specifically to Jupiter and its moons... calling the other giant planets "Jovians" is completely wrong. Just scrape nails on a chalkboard while you're at it...

Anyways... Jupiter and the other giant planets are mostly hydrogen and helium. Some of their atmosphere will freeze out and form a solid surface where the pressure is higher, but there will always be a gaseous layer above, and they probably won't change very much visibly, although their size should contract.

Look at a phase diagram for hydrogen and helium.

 

[redwood973]

Actually TechNoir, you have a point. The only reason Juipiter gives off more energy than it receives is due to the pressure it's under due to it's own mass. When the sun becomes a red giant, Juipiter will lose a lot more of it's atmosphere than it does now. So by the time the sun is a black dwarf, Juipiter's mass will be less and perhaps not enough to sustain it's pressure enduced energy production.

Sorry, pergradus. Old habbits are hard to break (although I have to admit, I easily adjusted to Pluto's fall from planethood).

 

[TheTechNoir]

Thanks for answering. :) Also, when you say old habits do you mean you just had a habit of calling the other giants Jovian planets or did they actually get referred to or classified as Jovian at some point in the past? If so, interesting I never knew that. I was going to correct you as well but didn't think I'd bother and I did get the impression you knew better. Either way irrelevant detail fortunately for the topic as long as we know which planets you are referring to.

 

[FtlIsAwesome]

I was under the impression that "jovian" (lowercase) can refer to any gas planets, while "Jovian" (uppercase) usually refers specifically to Jupiter. I've seen Uranus and Neptune called "jovians" and at other times "subjovians". But as you said, it doesn't really matter.


Do Jupiter's moons receive more energy from Jupiter than from the Sun?

(although I have to admit, I easily adjusted to Pluto's fall from planethood).

They demoted Pluto because the cats were demanding it. I would have preferred they gave planet status to a cat instead, then they'd be balanced.

 

[TheTechNoir]

I will state facts, and things I think are facts but am not super 100% certain about so I will let someone else confirm those bits.

Some of Jupiter's moons, such as Europa receive a tremendous amount of energy because of the tidal forces it experiences when traversing Jupiter with it's non-perfect orbit (illiptical orbit I believe?). This I am certain of, some of Jupiter's moons get tugged and stretched in different directions as they orbit causing intense heating friction (it is for instance what it is believed to be a heating source of Europa's believed sub-surface ocean). This I am certain about, whether it receives more energy from tidal processes than the sun I am not 100% positive but I strongly believe so. As for some of the other moons not effected so much or as close to it's EM field/as radiation bathed I'd imagine that the sun may provide more energy for some of them. But that is pure guess based on little.

 

[FtlIsAwesome]

All objects have elliptical orbits. For most objects in the solsys they are very close to a circle, but not quite. Europa has an eccentric orbit. Tidal heating is also present on Io making it the most volcanicaly active world in the solar system.


This isn't really related to anything, and you probably already know it...
Fun fact: Ganymede is larger than Mercury

 

[redwood973]

[W]hen you say old habits do you mean you just had a habit of calling the other giants Jovian planets or did they actually get referred to or classified as Jovian at some point in the past?

Way back in the day when in elementry school we were taught the planets could be divided into two groups, the inner terrestrial planets and the outer jovian planets. Hard for me not to think of the outers as something other than jovians. And as FtlIsAwesome said, I too am under the impression Jovian referst to Juipiter or it's surrounding bodies.

I've seen Uranus and Neptune called "jovians" and at other times "subjovians".

It seems, from what I've seen, there is a trend to refer to Jupiter and Saturn as gas giants; while Uranus and Neptune are trending to be called ice giants due to their much different composition and states as compared to the first two. I've also found some references to "dwarf giants" in relations to jovians smaller than Uranus and Neptune (but still larger than Earth). I'm not finding much information on these "dwarf giants" since no examples exist in our system they appear to be theoretical.

Do Jupiter's moons receive more energy from Jupiter than from the Sun?

It is correct that most of the moons of Juipiter and Saturn receive most of their energy in the form of tidal stress. I don't believe any moons of the jovians are close enough to their parenty body to receive any benefit from the mass enduced energy the jovians (may) release (I still can't find proof anybody other than Juipiter produces any amount of energy).

They demoted Pluto because the cats were demanding it. I would have preferred they gave planet status to a cat instead, then they'd be balanced.

I found it easy to give up Pluto as early in our studies of the solar system I stumbled upon an anstronomer who shorlty after Pluto's discovery said it wasn't a planet but similar to the bodies of the asteroid belt, but much larger in scale. What he said made sense, so I've always considered Pluto a non-planetary body (of course today we have the terms Kuiper Belt/Oort Cloud as descriptors).

And yes, I consider the Kuiper Belt/Oort Cloud to be the same thing. The KB appears simply to be the leading edge of the OC; the gap between the two is simply the result of something clearing the area similar to the gaps in the asteroid belt or in the rings of Saturn.

Fun fact: Ganymede is larger than Mercury[.]

Fun fact: when the sun becomes a red giant, the larger moons of Juipiter and Saturn will become more and more earth-like and most likely will be come habitable. We'll lose the Earth, but have a handful of Earth-like replacements! Cool.

 

[FtlIsAwesome]

Ok, I'm not sure you got the joke.

I was talking about Pluto the dog.

 

[qraal]

Actually TechNoir, you have a point. The only reason Juipiter gives off more energy than it receives is due to the pressure it's under due to it's own mass.

Well, kind of. The heat inside is from Jupiter's contraction - gravitational energy being converted into frictional heating. The pressure opposing Jupiter's steady contraction is from that heat as well as the electrostatic forces of the component atoms.

When the sun becomes a red giant, Juipiter will lose a lot more of it's atmosphere than it does now. So by the time the sun is a black dwarf, Jupiter's mass will be less and perhaps not enough to sustain it's pressure enduced energy production.

Ah, no. Most of the heat is in the core and it might be quite hot for some time afterwards. The heat makes (part of) the pressure which keeps Jupiter "up" against gravity. Eventually it might cool sufficiently for the hydrogen/helium to condense, but a LOT of heat must be released, via a currently cool photosphere, before that occurs.

Secondary issue is mass-loss. The Sun peaks at ~2730 times present luminosity, while losing about ~33% of its mass. Jupiter will thus orbit at ~1/0.67 times its present radius of 5.2 AU. Thus average insolation will be ~2730/(7.7)^2 = 45.3 times the Earth's current levels. No doubt Jupiter's exosphere will expand mightily and there will be some mass-loss, but the peak luminosity of the Sun lasts a very brief time in cosmic terms and extensive mass-loss is very unlikely.

 

[IsometricPion]

the mass enduced energy the jovians (may) release (I still can't find proof anybody other than Juipiter produces any amount of energy).

It seems that a combination of radioactive materials and changes in structure (such as shrinking with the associated release of gravitational potential energy as heat) are thought to produce heat in all of the gas giants (at least in our solar system, though probably in others as well). Google books has "Giant planets of our solar system: atmospheres, composition, and structure" "By Patrick Irwin", pages 62-65 give short summaries about internal heat generation in each of the gas giants. It seems the generation of heat via the release of gravitational potential energy due to shrinking of a planet is referred to as the Kelvin-Helmholtz mechanism (the wikipedia page on this topic references the part of the book I cited above, but was otherwise somewhat unhelpful).

 

[TheTechNoir]

All objects have elliptical orbits. For most objects in the solsys they are very close to a circle, but not quite. Europa has an eccentric orbit. Tidal heating is also present on Io making it the most volcanicaly active world in the solar system.This isn't really related to anything, and you probably already know it...
Fun fact: Ganymede is larger than Mercury

Oops! Yeah, elliptical orbit was the word I was trying to think of, thx.

 

[DaveC426913]

ugh... Jovian refers specifically to Jupiter and its moons... calling the other giant planets "Jovians" is completely wrong.

False.

I was under the impression that "jovian" (lowercase) can refer to any gas planets, while "Jovian" (uppercase) usually refers specifically to Jupiter. I've seen Uranus and Neptune called "jovians" and at other times "subjovians".

True.

 

[TheTechNoir]

agh typo again***eccentric orbit

 

[FtlIsAwesome]

I'll also point out that "terrestrial" is based from "terra": Earth.
But we're derailing ourselves here.


Back to the subject...

What would happen, instead, the sun suddenly disappeared? How would this affect the gas giants? This scenario is different as it omits the other changes to the solar system from long periods of time.
And how does this compare to realistic scenario?

 

[TheTechNoir]

Yes also Venusian for Venus, Martian for Mars, etc.

I think the problem with your question, even as a thought-exercise is it isn't based in reality. Unless you can propose a scenario that, while maybe incredibly unlikely to occur CAN occur then I don't really see how we can answer the question. Certain factors would cause the sun to 'vanish' or for us to immediately leave it's gravity well, and I think those factors would have a drastic impact on the answer of what would happen. Otherwise to try and answer would imo-be beyond speculation and in the make-belief sort of realm.

 

[FtlIsAwesome]

Actually, I don't think the lack of gravity would affect the jovian planets directly, only their trajectories.
The original question was how their composition would change with no light from the Sun, and the realistic scenario introduces other factors.

So our descendants millennia into the future encase the Sun in a http://en.wikipedia.org/wiki/Dyson_sphere" .
What happens to the jovian planets due to lack of light?
As others said, will they become solid or freeze? I doubt this.

 

[qraal]

Jupiter emits about 65% more heat than what it gets from the Sun. Thus it's effective temperature will decline only a bit if there was no Sun or a perfect occultation. Significant cooling will take many more billions of years because its photospheric temperature is relatively low and its effective opacity is very high. Same for all the jovians I suspect. In the case of Uranus and Neptune both would see condensation of their water/ammonia/methane mantles once the gaseous atmosphere had chilled sufficiently. Uranus has something causing blockage of heat flow from the interior, so its cooling might drag out longer than Neptune.

Given a trillion sunless years they should all be almost as cold as the CMB. By that stage they will be frozen solid, except for limpid pools of helium.

 

[FtlIsAwesome]

Given a trillion sunless years they should all be almost as cold as the CMB. By that stage they will be frozen solid, except for limpid pools of helium.

So eventually they will solidify, but not immediately.
Could you elaborate on what their composition will be in this frozen state?

 

[Chronos]

Try to avoid the abyss. The sun suddenly disappearing, along with its gravitational influence is science fiction. But, such an event would have a deleterious affect on planetary orbits. They would all vacate the premises on a tangent relative to their orbital trajectory. Personally, I would miss jolly old Jupiter in the night sky.

 

[qraal]

So eventually they will solidify, but not immediately.
Could you elaborate on what their composition will be in this frozen state?

Frozen hydrogen, liquid helium except past the 5 bar (IIRC) pressure level, which is the only way helium will solidify. Plus all the other constituents, all frozen solid... except... well there's the possibility that neutrinos might be captured and produce a trickle of heat in the iron component of the planet's core. In which case the heating will last for potentially ~10²³ years or so. See this recent preprint for a discussion...

http://arxiv.org/abs/1101.4172"

Addendum:

Helium's freezing point is 0.95 K at 2.5 MPa according to Wikipedia.