Which galaxies will become gravitationally bound to us after our collision with Andromeda?

[MarkE]

In about 4 billion years, these two spiral galaxies will merge together to form one big, much more massive, elliptical galaxy. How will other galaxies in the universe react to this (gravitationally)? Are there any other big collisions scheduled to occur?

Edited November 11, 2017 by MarkE

[mathematic]

Since both galaxies are mostly empty space, it is difficult to predict what happens when they meet.

[StringJunky]

Here's what wiki says about galactic collisions:

Quote

Such collisions are relatively common, considering galaxies' long lifespans. Andromeda, for example, is believed to have collided with at least one other galaxy in the past,[7] and several dwarf galaxies such as Sgr dSph are currently colliding with the Milky Way and being merged into it.

The studies also suggest that M33, the Triangulum Galaxy — the third-largest and third-brightest galaxy of the Local Group — will participate in the collision event too. Its most likely fate is to end up orbiting the merger remnant of the Milky Way and Andromeda galaxies and finally to merge with it in an even more distant future. However, a collision with the Milky Way, before it collides with the Andromeda Galaxy, or an ejection from the Local Group cannot be ruled out.[6]  https://en.wikipedia.org/wiki/Andromeda–Milky_Way_collision

 

[MarkE]

21 hours ago, mathematic said:

Since both galaxies are mostly empty space, it is difficult to predict what happens when they meet.

Are you saying it's not certain yet that they will merge to form one big galaxy?

[Airbrush]

Will all of the galaxies in the Virgo Supercluster eventually become one giant galaxy?  That is with the exception of a few galaxies that get ejected or torn apart during the mergers?

"In roughly 150 billion years from now, the remaining galaxies of the Local Group will coalesce into [one] object, that being the next evolutionary stage of the local group of galaxies."

https://en.wikipedia.org/wiki/Andromeda–Milky_Way_collision

Edited November 12, 2017 by Airbrush

[MarkE]

@Airbrush Will this increase of mass (multiple black holes merging into one big super-supermassive black hole) have influence on the 'heat death of the universe' hypothesis?

[Airbrush]

Whatever happens with galaxy mergers within the Local Group, or even the entire Virgo Supercluster, will have no impact on the rest of the universe because all superclusters are isolated from all others.

[MarkE]

@@Airbrush Has it been measured that superclusters, who will become more massive in the future, won't ever be massive enough to have any gravitational impact on other superclusters?

[StringJunky]

14 minutes ago, MarkE said:

@@Airbrush Has it been measured that superclusters, who will become more massive in the future, won't ever be massive enough to have any gravitational impact on other superclusters?

Anything more than 200mlyrs apart will  have no effect on each other gravitationally and won't ever because of expansion by dark energy. Anything less than that distance can potentially overwhelm it and be influenced gravitationally.

This visualisation of the  structure at the supercluster level shows the gaps between the threads; these will get bigger and the threads will get thinner. The gaps represent where dark energy dominates.

Edited November 16, 2017 by StringJunky

[Airbrush]

2 hours ago, MarkE said:

@@Airbrush Has it been measured that superclusters, who will become more massive in the future, won't ever be massive enough to have any gravitational impact on other superclusters?

Superclusters do not become more massive in the future.  Their mass remains constant, only the matter within them gets rearranged.  Yes, they won't ever be massive enough to impact other superclusters. 

However I think the mass of a supercluster will slow down expansion between adjacent superclusters.  If there was no supercluster, and a void instead, the neighboring superclusters would expand away from each other faster.  Is that correct StringJunky?

Edited November 16, 2017 by Airbrush

[StringJunky]

23 minutes ago, Airbrush said:

..However I think the mass of a supercluster will slow down expansion between adjacent superclusters.  If there was no supercluster, and a void instead, the neighboring superclusters would expand away from each other faster.  Is that correct StringJunky?

Yeah, I wouldn't think it was all or nothing but I'm open to being corrected.

[J.C.MacSwell]

7 hours ago, StringJunky said:

Anything more than 200mlyrs apart will  have no effect on each other gravitationally and won't ever because of expansion by dark energy. Anything less than that distance can potentially overwhelm it and be influenced gravitationally.

This visualisation of the  structure at the supercluster level shows the gaps between the threads; these will get bigger and the threads will get thinner. The gaps represent where dark energy dominates.

Should there not be a pronounced blurring effect on light (all EM radiation) running such a gauntlet of differentiated expansion? More than simple lensing effects.

(I hope that is not too far off topic. I assume there may be a simple explanation not requiring a new thread)

[StringJunky]

12 minutes ago, J.C.MacSwell said:

Should there not be a pronounced blurring effect on light (all EM radiation) running such a gauntlet of differentiated expansion? More than simple lensing effects.

(I hope that is not too far off topic. I assume there may be a simple explanation not requiring a new thread)

I don't know what you mean. You mean WRT the visualisation?

Edited November 16, 2017 by StringJunky

[J.C.MacSwell]

Just now, StringJunky said:

I don't know what you mean.

If space is expanding more here, less there, quite a bit more here (where dark energy dominates), etc. etc. light following local geodesics would (I think, but obviously not so why not?) blur the light enough to make viewing of distant images impossible.

[StringJunky]

10 minutes ago, J.C.MacSwell said:

If space is expanding more here, less there, quite a bit more here (where dark energy dominates), etc. etc. light following local geodesics would (I think, but obviously not so why not?) blur the light enough to make viewing of distant images impossible.

I don't know. .

[Airbrush]

21 hours ago, J.C.MacSwell said:

If space is expanding more here, less there, quite a bit more here (where dark energy dominates), etc. etc. light following local geodesics would (I think, but obviously not so why not?) blur the light enough to make viewing of distant images impossible.

Space is not expanding here.  It only expands between superclusters, where dark energy overcomes gravity.

If viewing of distant images was rendered impossible, then obviously we could not see with the precision we do.  Since we can see with clarity to the edge of the observable universe, even the structure of newborn galaxies over 13 billion years old.  That means such blurring is not happening.

Edited November 17, 2017 by Airbrush

[J.C.MacSwell]

24 minutes ago, Airbrush said:

Space is not expanding here.  It only expands between superclusters, where dark energy overcomes gravity.

If viewing of distant images was rendered impossible, then obviously we could not see with the precision we do.  Since we can see with clarity to the edge of the observable universe, even the structure of newborn galaxies over 13 billion years old.  That means such blurring is not happening.

Right. So one might expect some distortion (If it expanded evenly there would still be redshift but no distortion)

Any thought on why, given the uneven expansion, we are getting as clear a picture as we do after13 billion years of light travel?

Is it simply not enough distortion of space to matter, or is there some compensating effect I am missing?

Edit: Or I guess alternatively, is there simply no distortion despite the uneven expansion (I can't picture how that could be possible) or the distortion of space somehow has no effect on the paths of the light (I can't picture that either...not that nature owes anything to my expectations)

Edited November 17, 2017 by J.C.MacSwell

[StringJunky]

34 minutes ago, J.C.MacSwell said:

Right. So one might expect some distortion (If it expanded evenly there would still be redshift but no distortion)

Any thought on why, given the uneven expansion, we are getting as clear a picture as we do after13 billion years of light travel?

Is it simply not enough distortion of space to matter, or is there some compensating effect I am missing?

Edit: Or I guess alternatively, is there simply no distortion despite the uneven expansion (I can't picture how that could be possible) or the distortion of space somehow has no effect on the paths of the light (I can't picture that either...not that nature owes anything to my expectations)

Maybe what what we see is how things look from across the void, between the cobwebby areas where expansion is happening, but not how things actually are if we were closer to them. As Airbrush says, within gravitationally bound areas everything is as we expect.

Edited November 17, 2017 by StringJunky

[J.C.MacSwell]

14 minutes ago, StringJunky said:

Maybe what what we see is how things look from across the void, between the cobwebby areas where expansion is happening, but not how things actually are if we were closer to them. As Airbrush says, within gravitationally bound areas everything is as we expect.

OK. Thanks to you both. I am no doubt overestimating the potential of the effect. 

[StringJunky]

12 minutes ago, J.C.MacSwell said:

OK. Thanks to you both. I am no doubt overestimating the potential of the effect. 

We need mordred or Janus to chime in really.

[Mordred]

Distortion would arise if there is curvature, this is literally the fundamental aspect behind GR and the FRW on curvature is how it affects lightpaths via null geodesics. A flat universe light rays don't diverge nor converge. A curved universe they will diverge on negative curvature, converge on positive. 

The CMB measurements uses this principle to test for curvature (specifically looking for such distortions).

Another example being lensing (in this instance the curvature is such to cause magnification). A little side note Hubble uses these lenses to extend its range. ie those earliest galaxies or more often than not found via Hubble using a gravitational lens

Don't confuse this with redshift, this alters the frequency not the path specifically.

Edited November 18, 2017 by Mordred

[StringJunky]

31 minutes ago, Mordred said:

...Don't confuse this with redshift, this alters the frequency not the path specifically.

Thanks Mordred. I think this answers JCM's question. Does the rate of expansion vary where there is near parity between the of Dark energy and two adjacent superclusters?

Edited November 18, 2017 by StringJunky

[zapatos]

5 hours ago, Airbrush said:

Space is not expanding here.  It only expands between superclusters, where dark energy overcomes gravity.

I'm not sure what you mean by this exactly, but it is my understanding that space expands uniformly throughout the universe. It is true that the distance between gravitationally bound objects will not expand due to expansion of space, but we don't exclude the space within a supercluster when calculating how much a given section of space will expand. The expansion of space even occurs between your ears!

[Mordred]

Dark energy being a scalar uniform distribution by itself no. Distortions arise from density anistrophies (including those caused by thermal hydrodynamics)

 Gravity wells can cause localized distortions via the same mannerism above as gravity affects the mean density of particles in a given overdense region. DE the mean average in voids where it has measurable influence is constant.

 This also sets s boundary we use to place a limit to the size of a galaxy. When the mean density due to a gravity falls less than 200 times the critical density is the galaxy boundary. Ie this is the point Lambda has measurable influence

 

12 minutes ago, zapatos said:

I'm not sure what you mean by this exactly, but it is my understanding that space expands uniformly throughout the universe. It is true that the distance between gravitationally bound objects will not expand due to expansion of space, but we don't exclude the space within a supercluster when calculating how much a given section of space will expand. The expansion of space even occurs between your ears!

  the expansion of the universe only applies to regions not gravitationally bound. They are in collapsing states via Jeans instability. The boundary see above quote.(x-post)

Higher than above value a LSS is collapsing, same value applies to LSS as a galaxy though obviously applicable distances will vary. (this boundary includes DM distribution) due to formation distribution. 

 

Edited November 18, 2017 by Mordred

[StringJunky]

7 minutes ago, zapatos said:

I'm not sure what you mean by this exactly, but it is my understanding that space expands uniformly throughout the universe. It is true that the distance between gravitationally bound objects will not expand due to expansion of space, but we don't exclude the space within a supercluster when calculating how much a given section of space will expand. The expansion of space even occurs between your ears!

Yes, that's as I understand it. it's happening everywhere but only affects where the distance is great enough and gravity is low enough.

9 minutes ago, Mordred said:

Dark energy being a scalar uniform distribution by itself no. Distortions arise from density anistrophies (including those caused by thermal hydrodynamics)

 Gravity wells can cause localized distortions via the same mannerism above as gravity affects the mean density of particles in a given overdense region. DE the mean average in voids where it has measurable influence is constant.

 This also sets s boundary we use to place a limit to the size of a galaxy. When the mean density due to a gravity falls less than 200 times the mean density of Lambds is the galaxy boundary. Ie this is the point Lambda has measurable influence

 

Thanks.