Rotating Galaxies: Milky Way, Local Group & Beyond

[PhanthomJay]

Does the Milky Way galaxy, along with several other galaxies in the Local Group, orbit about the centre of that Local Group, and does the center of the Local Group orbit about some other center, etc.??, or is it just the stars that orbit their galactic centers?

 

[nismaratwork]

Does the Milky Way galaxy, along with several other galaxies in the Local Group, orbit about the centre of that Local Group, and does the center of the Local Group orbit about some other center, etc.??, or is it just the stars that orbit their galactic centers?

Globular clusters can orbit galaxies, but to answer your question, no. There is no barycenter around which galaxies in the Local Group or otherwise orbit, they are simply gravitationally bound.

To edit, I take this back. Our galaxies do not orbit EACH OTHER, but the local group has a center of mass, and looking at the supercluster we belong to, we do orbit a center of mass. Our Local Supercluster (Virgo et al) is the limit to this observation.

 

[nismaratwork]

To correct again, it is better to say there is a common rotation and merger, but orbit is probably not the correct term. You have to consider the expansion of space, the merging of galaxies, and the time and distance involved. If you take this to a logical extreme, then there would be a center to the universe around which there is rotation, and the notion of a rotating universe alone is a tough one. The notion that our universe has a center seems AFAIK to be discredited.

 

[PhanthomJay]

OK, thanks. I gather that the Milky Way and our Local Group of galaxies is moving toward some mysterious huge mass known as the Great Attractor, and that such motion is along a space-time geodesic, rather than an orbiting type circular or elliptical motion around it?'

 

[nismaratwork]

OK, thanks. I gather that the Milky Way and our Local Group of galaxies is moving toward some mysterious huge mass known as the Great Attractor, and that such motion is along a space-time geodesic, rather than an orbiting type circular or elliptical motion around it?'

It seems to be the case, or something close to that. The problem is that every time you bump up the scale to understand problem A, you find that you've uncovered a new need to increase the scale again.

 

[PhanthomJay]

If the Milky Way is 'orbiting' about the center of the Local Group, and that center in turn is moving at some ridiculous speed toward the Great Attractor, is the Great Attractor also moving toward some other ridiculously large massive cluster, or does the buck stop there and the Attractor is just sort of hanging in free space (not including space-time expansion) without any particular motion??

 

[nismaratwork]

If the Milky Way is 'orbiting' about the center of the Local Group, and that center in turn is moving at some ridiculous speed toward the Great Attractor, is the Great Attractor also moving toward some other ridiculously large massive cluster, or does the buck stop there and the Attractor is just sort of hanging in free space (not including space-time expansion) without any particular motion??

Beats me!

 

[Chronos]

This is all well and good, but, does not suggest the universe is rotating. The axis of rotation of local galaxies are randomly distributed. There is no preferred distribution as suggested if the universe itself was rotating.

 

[nismaratwork]

This is all well and good, but, does not suggest the universe is rotating. The axis of rotation of local galaxies are randomly distributed. There is no preferred distribution as suggested if the universe itself was rotating.

I never said that it was, or implied that it was, although it's possible it seems very unlikely.

 

[PhanthomJay]

Let's forget the words 'rotation' or 'orbit'.The Earth is moving around the sun. The sun is moving around the center of the Milky Way. The Milky way is moving around the center of the Local Group. The center of the Local Group is moving toward that Great Attractor. Everything is moving. I see no reason why the Great Attractor is also not moving toward something, and that something must be moving toward something else. Movement without end, Amen?

 

[nismaratwork]

Let's forget the words 'rotation' or 'orbit'.The Earth is moving around the sun. The sun is moving around the center of the Milky Way. The Milky way is moving around the center of the Local Group. The center of the Local Group is moving toward that Great Attractor. Everything is moving. I see no reason why the Great Attractor is also not moving toward something, and that something must be moving toward something else. Movement without end, Amen?

Movement to the limits of our current observational capacity, amen. ;)

 

[Bluedust]

And then eventually they will all attract together again and cause another Big Bang?

 

[DaveC426913]

...does the buck stop there and the Attractor is just sort of hanging in free space (not including space-time expansion) without any particular motion??

Pretty hard to tell. It gets pretty sketchy to decide what is movement at this scale. Since we don't really know what this Great Attractor is or where it is, you can deduce that we're sort of poking about in the dark.

 

[DaveC426913]

And then eventually they will all attract together again and cause another Big Bang?

That scenario's likelihood is vanishing rapidly (if not completely debunked already). The expansion of the uiniverse is overwhelming the attraction on larger scales. The Big Freeze is looking to be the more likely. We end up in an observable universe devoid of any other galaxies but those gravitationally bound to us. Beyond a few million light years, the universe is completely barren.

 

[nismaratwork]

That scenario's likelihood is vanishing rapidly (if not completely debunked already). The expansion of the uiniverse is overwhelming the attraction on larger scales. The Big Freeze is looking to be the more likely. We end up in an observable universe devoid of any other galaxies but those gravitationally bound to us. Beyond a few million light years, the universe is completely barren.

It really puts a whole new spin on, "this is a great time to be alive"... :wow: