Dark matter might cause neutron stars to collapse into black holes

English: Vector compound of File:Neutron_star_...
(Photo credit: Wikipedia)

ratamacue0 called my attention to this interesting article on the possibility of dark matter “eating” neutron stars: Dark matter: Devourer of stars | Ars Technica.

Neutron stars are collapsed stars that have used up all of their fusion fuel.  Typically what happens at that point in a star’s life is that they collapse, but the extent of the collapse is largely a factor of how much mass they had.  A star the size of our sun will collapse into a white dwarf (dense but still composed of atoms with electron clouds), but a heavier star will often collapse into a much denser neutron star (the gravity has crushed the electron clouds out of existence with only neutrons left, at least at their core).  Heavier stars yet will collapse into black holes (where the gravity overwhelms all repulsive forces between particles and causes the whole structure to collapse into an infinitely dense point, a singularity).

Apparently, the problem is that there aren’t as many neutron stars at the center of the galaxy as there should be according to astrophysical predictions.  One possible explanation is that, over time, heavy neutron stars attract too much dark matter into their cores, and that the additional mass collapses them into black holes.  It’s an interesting theory, but as the article describes, it’s just one of many possibilities.

But reading this article made me wonder how much of the mass of the super-massive black hole at the center our galaxy might be composed of dark matter.  Or if it’s possible for dark matter in other regions to collapse into a black hole without ever going through the star stage.  It seems like it would depend on to what extent dark matter interacts with itself.

And that gets the the problem with any theory involving dark matter.  We just don’t know what it is yet.  Dark matter is only detected by its gravitational effects.  No one has yet managed to detect it in any other way.  There are lots of ongoing experiments to do just that.  Hopefully one of them will eventually make that detection, and the nature of it will tell us more about what appears to make up the majority of the matter in the universe.

6 thoughts on “Dark matter might cause neutron stars to collapse into black holes

  1. We know DM interacts with gravity and has mass. Anything with mass can form a black hole — it’s purely a matter of enough mass in a small enough volume. The question I have is whether there’s enough DM in one place to seriously affect a neutron star, let alone create its own BH.

    How borderline would the neutron star have to be for X amount more of mass to cause collapse? (Interesting thought: what would it be like when it was one atom away from collapse mass?)

    Given that DM doesn’t interact with elect.mag, weak or strong forces, it’s hard to see how it could interact with itself, except though gravity. As I understand it, the “halo” of DM around each galaxy is due to each individual particle in its own orbit around the galactic mass.

    (A question I have is whether DM was attracted to galaxies or did galaxies form around clumps of DM? I suppose both happen, but is one more the primary scenario than the other?)


    1. From what I understand, dark matter was necessary for galaxy formation, so I think the answer to your question is that galaxies form around clumps of DM.

      The question of what a neutron star would be like if it were one atom short of the mass needed for collapse into a black hole is an interesting one. There’s been speculation of quark stars, or even preon stars (if preons exist). http://en.wikipedia.org/wiki/Exotic_star
      Along the same lines, I’ve wondered what a white dwarf just short of the mass needed to ignite a type 1A supernova might be like. (Of course, in these cases, if you’re close enough to observe, you’re most likely about to die.)


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