• Question: This week, in the New Scientist, the cover article is about the fact that our previous theory of galaxies having bulges in the center of them is largely incorrect. One of the theories which would allow this to occur is if galaxies reached their final form in much quicker time than previously theorized. But, the problem is, we don't know how these galaxies could of formed at a quicker pace, as previously we haven't really been thinking of this. In your opinion, under what circumstances is it most likely that galaxies could of formed faster, and if related to the theoretical properties of dark matter, what would be the consequences in the rest of science if this theory was to be accepted as the most likely.

    Asked by fauxvive to Arttu, Ceri, James_M, Monica, Philip on 14 Jun 2011.
    • Photo: Arttu Rajantie

      Arttu Rajantie answered on 14 Jun 2011:

      One explanation for the missing bulges is that dark matter is “warm”. This means that they interact so weakly with other particles that they would have decoupled when they were still relativistic and the universe was hot. After that they would have cooled down faster than the rest of the universe, which is why they are “warm” as opposed to “hot”. Candidates for warm dark matter are gravitinos and sterile neutrinos. Unfortunately it would be difficult to find these directly at LHC.

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