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wreckhur
2014-Mar-28, 09:53 AM
I am having trouble understanding what or where the Great Attractor is. Is it in our visible universe? Do we know what it is or what it could possibly be? Is there something even more massive than the Great Attractor pulling on the Milky Way? Finally, if the universe is expanding and all Galaxies are moving away from each other, how can it be that all of these Galaxies are being pulled towards one spot? Thank you in advance.

Cougar
2014-Mar-28, 10:44 PM
Well, you can check out the wiki article (http://en.wikipedia.org/wiki/Great_Attractor) on the Great Attractor. It's a huge supercluster of tens of thousands of galaxies that's less than a billion lightyears away. That amounts to a lot of mass. As wiki notes:


...this mass is observable by its effect on the motion of galaxies and their associated clusters over a region hundreds of millions of light-years (http://en.wikipedia.org/wiki/Light-year) across. These galaxies are all redshifted (http://en.wikipedia.org/wiki/Redshift), in accordance with the Hubble Flow (http://en.wikipedia.org/wiki/Hubble_Flow), indicating that they are receding relative to us and to each other, but the variations in their redshift are sufficient to reveal the existence of the Great Attractor.

Cougar
2014-Mar-28, 10:52 PM
Oh, and it's in the direction of the other side of our galaxy, so we have to look through all the stars and gas and dust of our own galaxy just to see it. Well, it can't be seen in visible light wavelengths, so other wavelengths are required to do the "seeing".

Alan Dressler's Journey to the Great Attractor tells all about the difficulties and detection of this huge conglomeration of mass....

wreckhur
2014-Mar-29, 05:56 AM
Thank you Cougar that is very interesting.