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Our Local Group's Microwave Background Radiation dipole

  1. Jul 12, 2008 #1
    Why isn't our Local Group's dipole for Microwave Background Radiation pointed towards the center of mass for our Local Supercluster? Clusters are suppose to be just infalling towards gravitational well of it's supercluster. http://en.wikipedia.org/wiki/Cosmic_microwave_background
    See anisotropy velocity relative to CMB section.
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  3. Jul 12, 2008 #2


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    Because there is a greater flow than this virgocentric flow. It takes the Virgo supercluster and the Hydra-Centaurus supercluster towards the "Great Attractor". This is probably a concentration of more superclusters having the Norma cluster at its center. The virgocentric flow takes place within this "river" of matter and galaxies and is about 200 km/s. However, the motion towards the Great Attractor is about 600 km/s, and is therefore one that is more visible in the CMB dipole.
  4. Jul 12, 2008 #3


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    We could be accelerating towards the centre of the Virgo cluster, but orbiting around it.

    Our motion relative to the CMB (allowing for our motion around the galactic centre) is roughly orthogonal to the direction of the centre of the Virgo cluster, just like the direction of the Earth's motion is more or less orthogonal to the direction of the Sun.

    Last edited: Jul 12, 2008
  5. Jul 13, 2008 #4
    Web site: http://en.wikipedia.org/wiki/Great_Attractor
    has a nice 2MASS etc. infrared sky. On large magnification, our Local Group's dipole in relation to CMB frame of reference is in direction of Hydra/Centaurus s.c.s at redshift Z .016 and .02. This is somewhat off from Shapely concentration at Z .048. This differs markedly from a Virgocentric infall. The image refers also to Norma s.c. Z .016 and nearby supposed G.A. which differs markedly from CMB dipole - contradiction? Also the text refers to Norma being near to Hydra/Centaurus - another contradiction?
  6. Jul 14, 2008 #5
    Another site with zoom graphics of superclusters. Hydra-Centaurus seems to be most common as what has been referred to as great attractor. http://www.atlasoftheuniverse.com/superc.html
  7. Jul 14, 2008 #6


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    I don't think this is correct. Carroll & Ostlie in "An Introduction to Modern Astrophysics" mention that the Hydra-Centaurus supercluster is also being pulled by the Great Attactor. Same you can read in this page here: http://www.solstation.com/x-objects/greatatt.htm. In wikipedia you can read that it is currently assumed to have the Norma cluster in its center.
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