Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: WhiAmI on 27/09/2010 18:36:21

Title: Are there dark matter stars?
Post by: WhiAmI on 27/09/2010 18:36:21

Are there dark matter stars? I use the term "star" loosly because a clump of dark matter would not shine. But dark matter should easily form black holes since there would be no degeneracy pressure to halt inflow. I have heard the explanation that dark matter was not able to cool, via EM radiation, after the BB and therefore the particles (if dark matter is a particle) are moving too fast to aggregate through gravity alone. But statistically there had to be some local pockets of "cool" dark matter; it is not absolutely smoothly dispersed through space. As a clump grows it will capture faster and faster moving particles up until an event horizon forms and then it captures everything. Therefore, is it not reasonable to expect that darkmatter stars exist and that they should be detectable when gravitationally bound to a normal star in a "binary system"?

Title: Are there dark matter stars?
Post by: Farsight on 27/09/2010 21:33:49

There's no actual evidence for any such stars, but people do talk about "boson stars". See http://www.jrank.org/space/pages/2242/boson-stars.html for a little more information, but do note that they are hypothetical, and rely upon "the favoured assumption is that the dark matter is made of fundamental particles". This has been under a little strain of late, because people looking for WIMPs can't find them. Personally I think it's the wrong assumption, because a gravitational wave and indeed a gravitational field is a "boson" of sorts, and it isn't made out of fundamental particles. 

Title: Are there dark matter stars?
Post by: Soul Surfer on 28/09/2010 00:24:03

Particle energy and angular momentum is a bigger barrier to collapse than you appreciate.  For stars to form the gas cloud has to get very cool indeed