# The Great Attractor

1. Mar 21, 2006

### Chaos' lil bro Order

I've recently heard of a region in space near our Milky way called the 'Great Attractor' that is sucking in our galaxy among others and even local clusters. Is this due to dark matter? I think the Milky way blocks our observation of it so we're left to perturbative principles, but can anyone tell me what we know about this region?

ty.

2. Mar 21, 2006

### mathman

Look up "Great Attractor" on Google.

3. Mar 21, 2006

### Chaos' lil bro Order

Ya good post. Look up 'unhelpful' on dictionary.com.

4. Mar 22, 2006

### kmarinas86

I think the point of this thread was to discuss the issue, not to ask for help :tongue2:

Some think not looking for the current content is laziness. I think that not creating content for others is laziness. :tongue2:

http://archive.ncsa.uiuc.edu/Cyberia/Cosmos/GtAttractor.html

To get to these speeds, it must have some time to accelerate. It could be dark matter, but I think it is quintessence, or something of that nature.

Hypothetically:
Quintessence could just be the nature of hyperbolic space between galaxies rather than a new class of particles. Galaxies could have repulsion between each other, and sometime the repulsion of two galaxies may be collective enough for one of those galaxies to jam itself into region of a third galaxy, creating either a large galaxy or a new cluster. This would explain the velocities without dark matter. Or you could have a combination of both!

5. Mar 23, 2006

### Chronos

I think mathman gave a helpful and appropriate answer. Albeit I would have suggested a search using 'cosmology great attractor', instead of 'the great attractor': which is liable to send you to a porn site!

Last edited: Mar 23, 2006
6. Mar 23, 2006

### Chaos' lil bro Order

ty kmarina.

Chronos, you don't actually think suggesting a google search is helpful do you? Is there a PF mandate that all scientific advisors have to back eachother up?

Why not answer every post with 'google it'? I think the beauty of this forum is custom made answers to questions beyond simple keywords.

7. Mar 23, 2006

### mathman

(Great Attractor)

A question like this can best be answered by looking up reference works. Incidentally, I checked Google before I responded - there wasn't any porn, at least in the first page.

8. Mar 23, 2006

### Soul Surfer

A great deal of work has been done on the relative radial velocities of stars in galaxies and galaxies themselves with the aim of trying to understand how things are moving about on the largest scale. Remember though that in this environment transverse velocities cannot be measured inly inferred. The statistical analysis if this shows some distortion from the classical even red shift (the further away the faster in a linear relationship) some of these residual motions can be inferred as clusters of galaxies orbiting a common centre but even when this has been taken into account there is still a non random residual in a particular direction. This direction is called the great attractor. This attractor is a long way from our galaxy but still relatively local compared with the size of the observable universe.

Tentative identifications have been made with a quite distant but very large cluster of galaxies

9. Apr 2, 2006

### robousy

The Great Attractor is very very far away from us. Billions of light years.

If you think of the sizes of structures in the universe then a galaxy is a pretty huge structure, containing billions of stars. Beyond galaxies, the next structure is galactic clusters, and, I believe, beyond that galactic superclusters.

Now, as far as I have read, the Great attractor is pulling the local group of galaxies towards it. I don't think we know what it is, it might just be the next level in the heirachy, eg a 'super mega uber cluster'.

Last edited: Apr 2, 2006
10. Apr 2, 2006

### mathman

http://csep10.phys.utk.edu/astr162/lect/gclusters/attractor.html

has the following paragraph.

Calculations indicate that ~1016 solar masses concentrated 65 Mpc away in the direction of Centaurus would account for this. This mass concentration has been dubbed the Great Attractor. Detailed investigation of that region of the sky (see adjacent image of the galaxy cluster Abell 3627) finds 10 times too little visible matter to account for this flow, again implying a dominant gravitational role for unseen or dark matter. Thus, the Great Attractor is certainly there (because we see its gravitational influence), but the major portion of the mass that must be there cannot be seen in our telescopes.

65 Mpc is roughly 200 million light years (not billions).

11. Apr 2, 2006

### Chaos' lil bro Order

I'm no astronomer, but 1016 solar masses doesn't seem like such a huge deal in the Universe considering there are what, over 100 billion galaxies? Althought, 65 Mpc is quite close to us considering the Universe's size to be ~4000 Mpc.

12. Apr 3, 2006

### matt.o

considering this 10^16 solar masses is probably contained in a 65 Mpc^3 volume, I don't think it is fair to compare it to the whole universe. Besides that, I don't really see the point in what you said.

13. Apr 3, 2006

### mathman

I suspect that the volume in question is very much smaller. The distance to it is around 65 Mpc.

14. Apr 4, 2006

### matt.o

no it is not. I worked that number out based on a run of the mill spherical cluster with virial radii of around 2.5Mpc. In fact, it is probably bigger than this. It may be that we are falling into the node of a filament. Considering the mass quoted - an order of magnitude more massive than a big cluster- I think the latter is true.

Last edited: Apr 4, 2006
15. Apr 4, 2006

### Chaos' lil bro Order

You made a mistake and said 1016 solar massaes, so I was misled. Its really 10 power 16.

16. Apr 4, 2006

### Chaos' lil bro Order

Where do you get 65 Mpc^3 volume from? No one ever said that to be the case, it was simply stated that the Great Attractor was 65 Mpc distant, not that this was its volume. I don't understand how you could misread such a thing.

Last edited: Apr 4, 2006
17. Apr 4, 2006

### matt.o

No, I have not made a mistake. We are being attracted to a mass (65Mpc away) of 10^16 solar masses - more massive than a massive cluster of galaxies (~10^15 solar masses). If we assume however that the mass we are being attracted to is a spherical cluster, then we can say that the mass is contained within 65 Mpc^3. This is assuming a virial radius of 2.5Mpc (an underestimate considering the mass). The volume of a sphere is $$4/3\pi \rm{r}^{3}$$ = 65 Mpc^3. This is an underestimate, so when mathman says he thinks it is contained in a smaller volume, he is wrong. So I think it is you who has mis-read.

So, I still don't understand why you are comparing this mass to the rest of the Universe. It seems a pointless exercise. Please explain.

##EDIT - Oh ok, you read it as 1016 solar masses.

Last edited: Apr 4, 2006