Galactic Sheets and Voids

[RJ Emery]

I’m interested in learning more about galactic sheets and voids. Via testimonials, what books or texts discuss and expound on that topic?

 

[pinball1970]

I’m interested in learning more about galactic sheets and voids. Via testimonials, what books or texts discuss and expound on that topic?

@Ibix or @Orodruin may have some pointers?

 

[Ibix]

Not really. My understanding of the details is limited - basically under-dense regions grow as over-dense regions collapse, so you end up with matter concentrated on the boundaries between under-dense regions. That necessarily forms large empty volumes separated by relatively thin sheets of dense regions.

 

[PeterDonis]

Moderator's note: Thread level changed to "B".

 

[pinball1970]

I’m interested in learning more about galactic sheets and voids. Via testimonials, what books or texts discuss and expound on that topic?

I had a quick Google because I have heard of the cosmic "web," the large scale structure of the universe.

Some information here. https://en.m.wikipedia.org/wiki/Galaxy_filament

Since this is a B thread I will stick a few more things in.

https://en.m.wikipedia.org/wiki/Void_(astronomy)

Also the Euclid space telescope is looking at the large scale structure of the universe from L2 where Webb is.

Some information on that here from the European Space Agency site.
https://www.esa.int/Science_Exploration/Space_Science/Euclid

 

[pinball1970]

A previous thread on voids on pf too.

Thread 'The Evolution of Galactic Scale Cosmic Voids' https://www.physicsforums.com/threads/the-evolution-of-galactic-scale-cosmic-voids.1060825/

 

[BWV]

Think about somewhere in one of these voids is a rogue star with maybe a planet with life that is too far from anything for any stars or galaxies to show at night, just blackness

 

[Vanadium 50]

What makes you suppose there is such a place? If you multiply the MW escape velocity by the age of the universe you get the size of the local group. Plenty to see.

 

[BWV]

What makes you suppose there is such a place? If you multiply the MW escape velocity by the age of the universe you get the size of the local group. Plenty to see.

Well the universe is big enough that anything physically possible probably has occurred.
This paper lists the fastest observed rogue stars at 700 km/sec or just over 0.002c
https://academic.oup.com/mnras/article/490/1/157/5104415?login=false

At 0.002c for 2 billion years is 4 million LY, beyond the range of what is visible to the naked eye, so it seems possible

Its cool and somewhat horrifying to think about at least

 

[Vanadium 50]

I don't think it is physically possible. Where is the gas? If you can't form the stars out there, and you can't move them out there, yiu won't have any out there.

 

[BWV]

I don't think it is physically possible. Where is the gas? If you can't form the stars out there, and you can't move them out there, yiu won't have any out there.

But various gravitational interactions can launch them out of galaxies

 

[Vanadium 50]

But various gravitational interactions can launch them out of galaxies

And we showed this gets you only a few million parsecs away at best.

Think of it this way - if you have active star formation, its a galaxy, not a void.

 

[BWV]

And we showed this gets you only a few million parsecs away at best.

Think of it this way - if you have active star formation, its a galaxy, not a void.

Voids have galaxies , they are defined by having far fewer - the Bootes Void has around 60, for example

What objects a few million parsecs can be seen with the naked eye? Andromeda is about the limit from Earth

 

[Vanadium 50]

Yes, but if you are in one of those galaxies, you are in one of those galaxies. You don't get the black sky you talked about.

Thus far, you have given no evidence besides "well, maybe you are juyst plain wrong". Maybe I am. Hard to argue against that. My point is that your require one of two conditions, neither of which we have ever seen:

(1) A single star forming outside of a galaxy. (Note that it would have to be a young Pop III star, none of which have ever been seen.

(2) A star ejected from its parent galaxy far in excess of escape velocity, which runs into virial theorem and other problems.

 

[BWV]

Yes, but if you are in one of those galaxies, you are in one of those galaxies. You don't get the black sky you talked about.

Thus far, you have given no evidence besides "well, maybe you are juyst plain wrong". Maybe I am. Hard to argue against that. My point is that your require one of two conditions, neither of which we have ever seen:

(1) A single star forming outside of a galaxy. (Note that it would have to be a young Pop III star, none of which have ever been seen.

(2) A star ejected from its parent galaxy far in excess of escape velocity, which runs into virial theorem and other problems.

What I provided was a paper documenting stars traveling at 700 km/s which is sufficient to travel several million LY, beyond naked-eye visible range over the lifetime of the star. If a star in within one of the many isolated galaxies in voids were flung out, then what I am speculating could be possible