Could an Interstellar Gas Planet Heat its Moon Without Fusion Ignition?

[Skyland]

Summary: Can an interstellar planet be hot enough to heat it's terrestrial moon without igniting fusion?

I am a science fiction writer, however I am studying astrophysics to better captivate audiences with real and believable plots,

The idea in question is an interstellar sub brown dwarf gas planet, with a massive and hot metallic core. Supporting a thick hydrogen atmosphere, and a large magnetosphere.

Orbiting closely is a terrestrial moon with liquid oceans, a dynamic core, sea floor volcanism (etcetera, basically an earthlike moon) that has is own satellite, with an elliptical orbit around the terrestrial moon causing tidal friction.

Is there a possibility that a rogue gas planet could heat its moon( in conjunction with factors on the moon and its satellite) to a surface temperature of 15°C?

 

[Ralph Rotten]

Hello Skyland. I too am a writer here to eat brains and gain their knowledge. :)

Yes. They believe that some of the fracturing and venting on Europa (I think) is due to Jupiter's gravity yanking the planet around which shifts the ice plates and creates heat...

But a dwarf creates a huge amount of radiation and magnetic field. Half of Juno is just shielding so it doesn't fry the instruments every time it passes. So although we see in visible light, what if there were a species whose light (and warmth) was radiation. Would a brown dwarf be a sun to them, essentially. A dark star.

PS: That's cool that you are using a moonmoon for your story. I am also using a moonmoon in my new story.

 

[Ralph Rotten]

This may be something to digest.
They found a rogue planet a while back.
A dozen times bigger than Jupiter.
And it's radiation belt was off the charts.
Rocky Rogue Giant found

 

[Skyland]

Yes, I'm trying to make a dark, life supporting moon that orbits an interstellar planet 6 times bigger than Jupiter but isn't quite yet a brown dwarf, which has it's own moonlet , one with a breathable atmosphere, but no plants for photosynthesis. The oxygen comes from electrolysis that happens due to natural occurring batteries, i.e acid rain over veins of dissimilar metals that ionize and separate water into hydrogen and oxygen.

The planet and its livable moon would be found on accident by a colonization vessel on it's way to another solar system, and would host a plethora of blind flesh eating alien speicies, bacteria , and diatoms (the first development of plant like mater on the planet, and have special organelle that illuminate phosphorus to complete photosynthesis on the dark moon)

i just was to get the mass, heat, elements, radiation, and everything right. and basically need it to be believable based on what we know to be factual.

 

[Ralph Rotten]

Here is Jupiter.
The lines are magnetic field, and the blue cloud in the middle is the radiation field.
Something 6 times bigger would likely have a radiation zone 6x bigger.
I could see life forms that would see it as a sun. If your eyes see in that spectrum, and radiation is like vitamin D to you, then it would be a great place to live.

Picture posted via my twitter account. Image courtesy of NASA's Eyes free app.

 

[Skyland]

I'm basically trying to have the moon have a magnetosphere strong enough to shield it from most of the radiation from the planet, so humans could also live on it, main reason for them going in and dying to the aliens.

 

[Ralph Rotten]

Ooooh, you could give it an elliptical orbit so part of the year they have to go underground as the moon passes through the edge of the radiation belt.

One thing you can also consider is if the moon is tidally locked then you can hide on the back side of the planet from most of the radiation. That side always faces away from the planet, so you could have a radioactive hot side, and a cold side. The hot side would likely have more tectonic activity. This would fit the description of Europa.

 

[Skyland]

That is an Interesting idea, and the life On this planet would have migratory instincts to burrow, and the discoverers of the planet could land a day or two before they emerge because they waited for it to be in a safer zone before landing, for the whole surprise

 

[Skyland]

https://www.physicsforums.com/threads/blood-moon-concept.972399/

 

[stefan r]

Ooooh, you could give it an elliptical orbit...

One thing you can also consider is if the moon is tidally locked...

To be both tidally locked and elliptical is not likely.

Is there a possibility that a rogue gas planet could heat its moon( in conjunction with factors on the moon and its satellite) to a surface temperature of 15°C?

I think you are talking about a brown dwarf. The satellite orbiting it is a planet. Rogue planets formed around a star and were ejected. That could make it difficult for the object to retain moons.

Brown dwarf and rogue planet are overlapping things if you look at just mass. A particular planet can be much more massive than some brown dwarf. The difference is how they formed.

Summary: Can an interstellar planet be hot enough to heat it's terrestrial moon without igniting fusion?

If you are talking about a brown dwarf then yes. It will follow the Hayashi track. There is a stack exchange post that might explain this well. Here is a chart:

The planet ("moon") you want your characters to land on can be in a fairly new system. If it is close enough for liquid water on the surface then you should also have enormous tides. 10^-4 luminosity would imply 100x closer orbit radius. Tidal forces are proportional to distance cubed. So even if the brown dwarf is two hundred times smaller than the Sun you still get five thousand times the solar tidal force on Earth (between 1 and 2 thousand times a spring tide).

Solar flares would be quite violent. The flares, tidal heating, magnetic induction, solar winds, and comet impacts would all add heat.

The temperature is dropping very quickly for evolution. The "habitable zone" will move toward the star (rogue planet) so that the habitable zone will only be there for a few million years. It will transition from a high pressure steam atmosphere to solid ice ocean surface.

 

[Skyland]

To be both tidally locked and elliptical is not likely.
I think you are talking about a brown dwarf. The satellite orbiting it is a planet. Rogue planets formed around a star and were ejected. That could make it difficult for the object to retain moons.

Brown dwarf and rogue planet are overlapping things if you look at just mass. A particular planet can be much more massive than some brown dwarf. The difference is how they formed. If you are talking about a brown dwarf then yes. It will follow the Hayashi track. There is a stack exchange post that might explain this well. Here is a chart:
View attachment 244235

The planet ("moon") you want your characters to land on can be in a fairly new system. If it is close enough for liquid water on the surface then you should also have enormous tides. 10^-4 luminosity would imply 100x closer orbit radius. Tidal forces are proportional to distance cubed. So even if the brown dwarf is two hundred times smaller than the Sun you still get five thousand times the solar tidal force on Earth (between 1 and 2 thousand times a spring tide).

Solar flares would be quite violent. The flares, tidal heating, magnetic induction, solar winds, and comet impacts would all add heat.

The temperature is dropping very quickly for evolution. The "habitable zone" will move toward the star (rogue planet) so that the habitable zone will only be there for a few million years. It will transition from a high pressure steam atmosphere to solid ice ocean surface.

thank you, this is very helpful information, I read that only there is only a 6% possibility of rogue planets that have been ejected to keep a moon, but I was also reading that there is a mass requirement to be a brown dwarf, so I was calling it a sub brown dwarf/ rogue planet, was also hoping to find the magic number in mass, velocity, distance, atmospheric pressure, magnetosheres, to have the terrestrial planet remain habitable for at least 10 million years, and perhaps have the alien inhabitants be adapted species from another world other than the one in question.

 

[Ralph Rotten]

Didja check out that article I linked about the massive rogue. Was that about the size you were thinking of, or a tad bigger?

 

[stefan r]

Didja check out that article I linked about the massive rogue. Was that about the size you were thinking of, or a tad bigger?

FYI more massive brown dwarfs are smaller.

 

[Skyland]

Yeah I've been more concerned with mass over size, but I think I'm just going to read more and eventually figure out what I'm going to have to smudge like all science fiction does,

 

[Ralph Rotten]

Don't smudge.
Fact is stranger than fiction, and people are stranger than fact.
As a reader I prefer a book that doesn't take liberties with established science.
Speculative science, in areas that are still in dispute, that I don't mind.