Ok, I’ve heard of it. I’m actually willing to believe it exists, but what is the proof? From what I gather, its existence is inferred from the fact that the Milky Way and the rest of the local group are flying toward it at some ungodly speed. But how does this prove that it exists? Acceleration is the hallmark of a force, not velocity. Has someone proven that we are accelerating in this direction? Are the galaxies around the Great Attractor (the Abell 3627 cluster) moving toward us or away? Could it be that we are all moving away from the Big Bang with it’s “center” being in the opposite direction of the Abell cluster? What exactly is the Straight Dope?
LARRY R. ABELL 3628 38 M JEFFERSONVILLE 369/437 IN 1:27:42
http://www.coolrunning.com/results/01/ky/Apr7_PapaJo_set4.html
IIRC, the Great Attractor is Azrael, Death of all worlds. According to Terry Pratchett, anyway.
The Big Bang had no center. Or, you could say the center is everywhere. The Big Bang was not a localized phenomenon that flung matter out into existing space. Space and time began with the Big Bang. It didn’t happen over there somewhere; it happened right here and everywhere.
Here’s somebody else asking this question and a High Energy Astronomer’sanswer. There’s even a link to a picture of it.
Do we know the distance to Abell 3627 and whether our local group of galaxies is gravitatinoally bound to it?
This website gives the distance to it’s center of mass as 65 mega parsecs. Which is about 212 million light years away.
And as for the bound part. That of course depends on how fast the universe will be expanding in the near future. I know a lot of science programs mention that with expansion someday all the galaxies in the sky will recede into the very far distance. But I also know that Andromeda is expected to slam into the Milky Way in … what is it 2.5 billion years? So I would say we are effected by it and attracted to it, but in the end, and I mean the end, we aren’t bound to it.
Even though gravity is a very weak force, every thing is bound together by it. The two smallest most distant pieces of mass are bound together by gravity. At least that is what Isaac Azimov told me.
All masses feel the gravity of other masses, but they are not necessarily bound by it.
If an object is “gravitationally bound” means that will orbit the center of mass of the system, rather than escaping.
In order to tell if an object, say a galaxy, is gravitationally bound, you need to know two things: the mass of the system, and the velocity of the object. The mass tells you the system’s escape velocity, and if the object’s velocity is greater than the escape velocity, it’s not bound.
Both these things are pretty tricky to measure, because these objects are so distant and huge and (compared to the length-scales involved) slow-moving.
The Local Group of 40 or so galaxies is not being separated by the expansion of the universe yet (the Local Group is still gravitationally bound-up), but our Local Group is being separated from the 125 billion or so other galaxies in the visible universe.
Collisions within the Local Group will still occur such as the one you mention. In fact, I think the Milky Way is currently in the process of colliding with a small galaxy called the Sagittarius Dwarf.
http://antwrp.gsfc.nasa.gov/apod/ap980216.html
others are probably not far behind…
http://antwrp.gsfc.nasa.gov/apod/ap010804.html
Thanks for all the answers, I’ll be awaiting the collision!
a little preview…
http://oposite.stsci.edu/pubinfo/pr/97/34/af1.html