1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Re: This Week's Finds in Mathematical Physics (Week 238)

  1. Aug 18, 2006 #1
    Some updates on the Bullet Cluster / dark matter saga.
    You can now see a picture of the Bullet Cluster here:


    I've also updated a bunch of information and fixed some mistakes
    in the initial version of "week238", thanks in part to Matt Owers.

    >Markevitch and company have been studying the "Bullet Cluster", a
    >a bunch of galaxies that has a small bullet-shaped subcluster zipping
    >away from the center at 4,500 kilometers per second.

    >It seems that one of the rapidly moving galaxies in this subcluster
    >has hit a bystander galaxy - I'm not sure, but a high-speed collision
    >of galaxies occurred.

    In fact, the whole subcluster hit another subcluster!

    So, the picture is a picture of colliding bunches of galaxies.
    The individual galaxies in these bunches mainly shoot right past
    each other - but the intergalactic gas in one bunch is hitting
    the gas in the other, and getting so hot it emits X-rays.

    >So, dark matter is seeming more and more real. In fact, last year
    >folks found evidence for "ghost galaxies" made mainly of dark matter
    >and cold hydrogen, with very few stars:
    >6) PPARC, New evidence for a dark matter galaxy,

    Apparently the consensus is now that this ghost, VIRGOHI 21,
    is hydrogen stripped off from a galaxy by the "wind" it felt
    as it fell into the Virgo Cluster. This effect is called
    "ram pressure stripping" - the gas of a galaxy can be stripped
    off if the galaxy is moving rapidly through a cluster, due
    to interaction with the gas in the cluster.
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Can you help with the solution or looking for help too?
Draft saved Draft deleted