We are the moon.

[Umbran]

Well, I wouldn't rule out double planet systems.

For a good look at a double-planet system, read Rocheworld by Robert L Forward. Forward's characterization isn't great, but his science is top notch.

How about something more exotic than a gas giant or brown dwarf? Like, say, a superdense chunk of neutronium, blasted off a neutron star eons past, that has somehow fallen into orbit around a normal star and aquired a life bearing moon? The orbit around such a thing could be very short, since it takes up far less space than a gas giant. It may even be shaped irregularly.

Okay...

This is unlikely to happen. Neutronium exists in gravitational fields strong enough to mash electrons into protons to make neutrons. There's very little binding those neutrons together in that dense configuration except the gravity. Take it out of that very strong gravity field, and you will quickly cease having so many neutrons packed in a small space, as there's now nothing to hold them there. Poof, no more solid object. Sci-fi notwithstanding, there's no reason to think that neutronium can exist outside of stellar-mass objects.

For a look at having life (not humanoid life, I assure you, but life nontheless) on the surface of a neutron star, check out Dragon's Egg and Starquake by Robert L Forward.

 

[Quip]

Well, thats the last time I make assumptions on matters of astrophysics.

Probably.

 

[Ferret]

Assume away. I didn't know what Umbran just said until now, and things can only get learnt by either 1)Asking questions, or 2) making a fool of yourself. I'm a big fan of the latter.

 

[Umbran]

Assume away. I didn't know what Umbran just said until now, and things can only get learnt by either 1)Asking questions, or 2) making a fool of yourself. I'm a big fan of the latter.

And hey, it isn't like other folks haven't been as bad. Even hard-sf writers like Larry Niven. I think he played the neutronium card when trying to come up with a material tough enough to be the structure of the Ringworld. But even the Pak aren't that good.

 

[Quip]

Well I usually like to know a few basics of whatever I'm talking about. At least make an attempt for reasearch. In this case, I was thinking of neutronium as just superdense matter, but appearantly its more like plasma thats not packed quite as tightly as a black hole.

I still like the idea of an odd chunk of heavy material floating around with a moon, with about the mass of a gas giant. Perhaps, the molten iron core of a large planet that was ejected when the planet was mostly obliterated by some impact. It then managed to cool off without attracting more material (seperated from the majority of the other debris) or collapsing into a regular shape (it was already beggining to cool), resulting in a massive porus irregular iron shape.

Fast foward millions of years later, this metal mass has been pulled into orbit around a forming star system. It manages to attract some amount of light material but only enough to give it a liquid/gas core, that isn't even half thick enough to cover the iron protrusions of its frame. It also catches a moon, which would have eventually been a planet itself were it not for the large, ferrous visitor.

This moon solidifies, matures, and eventually produces life, intelligence, and a really interesting view.


There, is that somewhat better astrophysics? Or at least plausible science fiction?

 

[Umbran]

In this case, I was thinking of neutronium as just superdense matter, but appearantly its more like plasma thats not packed quite as tightly as a black hole.

Well, at that density any normal person woudl call it solid, rather than plasma, but yeah.

It then managed to cool off without attracting more material (seperated from the majority of the other debris) or collapsing into a regular shape (it was already beggining to cool), resulting in a massive porus irregular iron shape.

That's not comletely implausible. However, any collision large enough to eject that core will cause massive melting, too. And if it's fluid when ejected, it'll come down into a roughly round shape. Anything large enough to hold an earth-sized body in orbit is likely to be round under it's own weight.

Of course, for a fantasy world, you can just toss the physics out the window.

 

[tarchon]

Well I usually like to know a few basics of whatever I'm talking about. At least make an attempt for reasearch. In this case, I was thinking of neutronium as just superdense matter, but appearantly its more like plasma thats not packed quite as tightly as a black hole.

I still like the idea of an odd chunk of heavy material floating around with a moon, with about the mass of a gas giant. Perhaps, the molten iron core of a large planet that was ejected when the planet was mostly obliterated by some impact. It then managed to cool off without attracting more material (seperated from the majority of the other debris) or collapsing into a regular shape (it was already beggining to cool), resulting in a massive porus irregular iron shape.

At least one probable quasi-terrestrial planet, mu Arae d, has been identified outside the solar system with about 14 earth masses, in orbit around mu Arae. That's thought to be about the upper limit for non-gas-giants. I suspect that metal-rich accretion disks probably tend to give very iron-rich inner planets, and that may be one of them. In our system, the silicates are still pretty significant even in the inner solar system, but perhaps the light-heavy element segregation is more pronounced under different conditions, so instead of a bunch of iron-silicate worlds and a bunch of hydrogen-water worlds, you get predominantly iron-metal worlds, iron-silicate worlds, and then hydrogen-water worlds. Though, you'd also expect that such systems would have even less volatiles remaining in the inner system as well.
mu Arae b is curiously an example of a (probably) jovian planet that lies in the "life zone," so the moons that it almost certainly has could have conditions rather similar to our inner solar system.

 

[Quip]

Well, at that density any normal person woudl call it solid, rather than plasma, but yeah.

I meant, like a solid plasma. Err... they're both normal matter transformed by intense energy... but plama is subatomic particles torn apart... and neutronium is subatomic particles fused togther... so its really the complete opposite... damn.

However, any collision large enough to eject that core will cause massive melting, too. And if it's fluid when ejected, it'll come down into a roughly round shape.

How about if it was scattered out in space for a long time then gravitated togther? That could produce the iron clump, but...

Anything large enough to hold an earth-sized body in orbit is likely to be round under it's own weight.

Yeah see, there I got thinking of iron as a solid, but on these scales structure never trumps gravity. I'm mesoscopically biased, it seems.

Of course, for a fantasy world, you can just toss the physics out the window.

I like to keep it as close as possible, unless I want to make a notable exception by way of magic. I could design a world of tangled time, space, and elemental planes, orbiting a giant ever shifting gem-like mass pulsating with the forces of law and chaos simultaneously, but thats a bit outside the context of this thread, methinks.

 

[Umbran]

I meant, like a solid plasma. Err... they're both normal matter transformed by intense energy... but plama is subatomic particles torn apart...

Your typical plasma is merely normal atoms with some electrons removed - ionized gases. Even in the heart of a star, you don't see too much in the way of subatomic particles.

Yeah see, there I got thinking of iron as a solid, but on these scales structure never trumps gravity. I'm mesoscopically biased, it seems.

Occasionally you can get structure to trump gravity on these scales, but you have to work at it a bit. You can imagine building a ringworld or finding a rocheworld or the like,but they're still pretty exotic.

 

[tarchon]

I meant, like a solid plasma. Err... they're both normal matter transformed by intense energy... but plama is subatomic particles torn apart... and neutronium is subatomic particles fused togther... so its really the complete opposite... damn.

Sometimes called a quark-gluon plasma, because, well, that's what it is. They're analogous to ion-electron plasmas in many ways.