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Name: Rosco
Status: other
Grade: n/a
Location: OR
Country: USA
Date: Winter 2011-2012


Question:
I read the article on dark matter and dark stars it: http://www.scientificamerican.com/article.cfm?id=dark-side-of-black-holes Why does dark matter not form dark stars or dark black holes since its affected by gravity?

Replies:
We know so little about dark matter that it is hard to say,

Not every free thing must fall into clumps, by the way... They say that gas and dust doesn't readily form stars until a) it is pretty dense and cool, plus, b) something throws a shock-wave into it, making small parts of it sharply denser, so peak gravity gradients form which are strong enough to overcome the remaining gas temperature. Perhaps condensation without events is inevitable, but would take longer than the age of the universe, so all the stars we actually see were "seeded" by some turbulent event...

Except perhaps old red-orange small stars in smooth undisturbed globular clusters, which kind of look to me like the "just falling together" situation. And you must wonder whether the early quasars did not just fall together. But I have not studied it.

It would be fairly reasonable for dark matter to be possessed of substantial kinetic energy and velocity, which would keep it diffusive, spread out and resisting compression. That would be a lot like an ideal gas that does not even bump itself. Then only gravity would affect a particle of it, and that only by bending its path around in large arcs. You can see those particles would be pretty unlikely to ever condense. They would need something that they interact with, so that the kinetic energy could be damped out. Physicists would say they need a way to be cooled down.

And we just do not know what the particles are or what they interact with, if anything, to do such cooling. Neutrinos, for example, interact with nearly nothing.

Jim Swenson


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