Do 'Ultracool' Brown Dwarfs Surround Us?

astroengine writes "The recent discovery of two very cool 'T-class' brown dwarfs in our cosmic neighborhood has prompted speculation that there may be many more ultracool 'failed stars' nearby (abstract). Not only are these objects themselves very interesting to study, should there be many such brown dwarfs spanning interstellar space. Perhaps they could be used as 'stepping stones' to the stars."

Re:fp

[TWX]

I guess we are in a world of shit if it turns out to be true.

Especially if they manage to show a link between this research, the fairly regular extinction events over the history of the planet, and The Nemesis Hypothetical Star [wikipedia.org]...

Re:Slingshot?

[Chemisor]

There will never be any interstellar trade. The distances and velocities involved require energy expenditures vastly higher than the cost of any valuables you may wish to transport. You might say the costs will be "astronomical". The only movement between stars will be radio signals and initial colony ships.

All foam, no beer

[MonsterTrimble]

The idea of Y-class brown dwarf stars are neat and all, but this whole 'stepping stone' idea is not really explained. Why would we use these as stepping stones? Is there an advantage to it? I don't understand why we would use them is all.

Re:All foam, no beer

[calderra]

Random ideas off the top of my head: Rogue stars of any sort might carry clouds of hydrogen and/or other elements, possibly even rocky asteroids and protoplanets, with them. It might be possible to refuel in one of these systems. Gravitational slingshots become an interesting idea, possibly allowing for some really interesting maneuvers. A gravity source also makes orbiting possible, so we could send ahead robotic probes to orbit some big external fuel tanks to await a manned mission that will carry less mass on-board and pick up supplies along the way- the probes can use gravitational assist to cut down on fuel use when stopping and rejoining the manned mission. There's just all sorts of potential, although again I'm mostly talking about any rogue star and not just brown dwarves.

Re:The only thing that surprises me is surprise

[delt0r]

The number of extra planets or dark stars you would need to matter, *would* show up because there would need to be soo many. They have been looked for you know. For example if there are millions more of these cold brown dwarfs than what we already have estimated, then the average distance to them would be so small that we would be able to observe many of them (probably would imply at least a few within the ort cloud). We would see many more micro-lensing events ... etc etc.

You can't have your cake and eat it too. If there is enough to explain dark matter, there is more than enough that observing them would be quite trivial.

On top of all that, such objects do not explain other observations of dark matter. In particular, the bullet cluster. We can in fact "see" dark matter.

Could we blow them up? (Pure speculation).

[wisebabo]

So these brown dwarfs are essentially big balls of (mostly) hydrogen with the centers under tremendous pressures and temperatures but not quite hot enough to "light" (in a fusion sense). Well what would happen if you managed to drop a fusion bomb on it? (On or near the surface where the temperatures are low but the high gravity might still compress the hydrogen into the megabar range).

While (probably) it would just fizzle, could the concentrated energy ignite just enough so the whole star went boom? (Like a Type I supernova?). I mean the "temperature" of an H-Bomb is in the hundreds of millions of degrees maybe it just requires one tiny (if an H-Bomb is "tiny") spark. Just like you can pour millions of gallons of gasoline on a barely sub-critical mass of Uranium and it won't go bang but one small neutron generator and you've got a mushroom cloud. While the impacts of asteroid and larger bodies could deliver a lot more energy, an H-Bomb could do so more INTENSELY.

I guess this is what the first H-Bomb scientists were worried about when they feared the first H-Bomb *might* ignite the water vapor in the atmosphere and consume the entire world. Just how easy would it be to blow one of these things up? Could you do it with even smaller cooler less dense bodies, say Jupiter (as proposed by sci-fi writer Charles Sheffield) or Neptune? (Tried it on earth, nope doesn't work). Lastly, our sun is already alite, but the RATE of fusion reaction is very slow (each gram of the sun produces far less energy per time than, say, a live elephant). Could we speed it up? Could an H-Bomb (or a suitably powerful laser such as was used in one of the Man-Kzinti war sci-fi books) trigger a local (or maybe not so local) explosion?

I guess this was the general idea behind the movie "Sunshine" (good movie). Seems they had some sort of very dense (causing a local gravitational field) fission bomb to re-ignite the sun. Wish they had a companion book to flesh out some of the details.

Anyway I know these ideas are probably non-sensical to any physicist but don't have enough math and physics knowledge to calculate it for myself. If anyone of you is so inclined and it won't take much time or effort, I'd appreciate the debunking (or not!) of this idle speculation.

(For even crazier speculation, how about igniting all that supposedly great fusion fuel Helium-3 that is just lying around on the lunar surface? Would it be enough to blow the moon out of orbit a la "Space 1999"?)

Re:All foam, no beer

[david.given]

Instead of building a colony ship that can travel a minimum of 4 ly to the next star system, you can build one that only needs to go 0.1 ly (or so, depending on the density of these things). That's a vastly simpler job, requiring much less time and energy, and possibly only taking a decade or so --- well within a human lifespan. Once you get to the brown dwarf, you colonise. Even a small brown dwarf like Jupiter has an insane amount of resources. Sure, there's no starlight, but if you've got hydrogen you can make your own. Eventually, when the population is big enough, it builds another colony ship to the next dwarf star.

So eventually you end up with a chain of thriving colonies from Sol to whereever your target star is. You don't have to rely on your ship carrying enough supplies to maintain a biosphere and civilisation for the whole, multi-hundred-year journey because you never go that far.

Of course, by then so much of your population will be living in deep space that the idea of setting up home next to a star (nasty, hot, dangerous things) probably isn't appealing any more...