Starship Asterisk*

Simulation TNG50: A Galaxy Cluster Forms

Explanation: How do clusters of galaxies form? Since our universe moves too slowly to watch, faster-moving computer simulations are created to help find out. A recent effort is TNG50 from IllustrisTNG, an upgrade of the famous Illustris Simulation. The first part of the featured video tracks cosmic gas (mostly hydrogen) as it evolves into galaxies and galaxy clusters from the early universe to today, with brighter colors marking faster moving gas. As the universe matures, gas falls into gravitational wells, galaxies forms, galaxies spin, galaxies collide and merge, all while black holes form in galaxy centers and expel surrounding gas at high speeds. The second half of the video switches to tracking stars, showing a galaxy cluster coming together complete with tidal tails and stellar streams. The outflow from black holes in TNG50 is surprisingly complex and details are being compared with our real universe. Studying how gas coalesced in the early universe helps humanity better understand how our Earth, Sun, and Solar System originally formed.

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I just did a few quick sums in my head to confirm that these solutions look about right.

Seriously, amazing stuff.

So let me understand this. This is gas mostly hydrogen that appears to be coming in from two directions, mostly bottom left and top right. Presumably this happened after the big bang and inflationary period where the universe expanded out in all directions. As the gas collides near the bottom center it rebounds back out to top left and right causing more collisions. Stars form and then galaxies which then cause a cluster. But if there was a single big bang , what caused the two original gas clouds to turn around and move toward each other? Seems their gravity would be about the same. Probably a closed universe where expansion was overcome by collapse. But today astronomers say the universe isn't closed but expansion is speeding up?

That is an awesome video...many effects of collisions...

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De58te wrote: ↑Tue Feb 26, 2019 8:37 am So let me understand this. This is gas mostly hydrogen that appears to be coming in from two directions, mostly bottom left and top right. Presumably this happened after the big bang and inflationary period where the universe expanded out in all directions. As the gas collides near the bottom center it rebounds back out to top left and right causing more collisions. Stars form and then galaxies which then cause a cluster. But if there was a single big bang , what caused the two original gas clouds to turn around and move toward each other? Seems their gravity would be about the same. Probably a closed universe where expansion was overcome by collapse. But today astronomers say the universe isn't closed but expansion is speeding up?

You're not looking at the entire universe here, just one tiny, tiny region of it. This region isn't large enough to see cosmological expansion at all. Of course, the whole region is being carried by expansion, but we don't see that because our frame of reference is set to the center of the developing cluster. So all we're seeing here are local gravitational interactions. The Big Bang left the gas distribution inhomogeneous, and so clumps are attracted to each other gravitationally, which is what's causing the collisions.

Chris Peterson wrote: ↑Tue Feb 26, 2019 2:14 pm

De58te wrote: ↑Tue Feb 26, 2019 8:37 am
So let me understand this. This is gas mostly hydrogen that appears to be coming in from two directions, mostly bottom left and top right. Presumably this happened after the big bang and inflationary period where the universe expanded out in all directions. As the gas collides near the bottom center it rebounds back out to top left and right causing more collisions. Stars form and then galaxies which then cause a cluster. But if there was a single big bang , what caused the two original gas clouds to turn around and move toward each other? Seems their gravity would be about the same. Probably a closed universe where expansion was overcome by collapse. But today astronomers say the universe isn't closed but expansion is speeding up?

You're not looking at the entire universe here, just one tiny, tiny region of it. This region isn't large enough to see cosmological expansion at all. Of course, the whole region is being carried by expansion, but we don't see that because our frame of reference is set to the center of the developing cluster. So all we're seeing here are local gravitational interactions. The Big Bang left the gas distribution inhomogeneous, and so clumps are attracted to each other gravitationally, which is what's causing the collisions.

• The Hubble Big Bang expansion is tracked by the evolving scale shown at the upper left.
  
  Top to bottom distance at end of clip ~ 2.85 Mpc versus the diameter of observable universe ~ 28,500 Mpc.
  
  Dark energy expansion is not supposed to have an effect on self contained entities such as galaxy clusters.

neufer wrote: ↑Tue Feb 26, 2019 4:01 pm

Chris Peterson wrote: ↑Tue Feb 26, 2019 2:14 pm

De58te wrote: ↑Tue Feb 26, 2019 8:37 am
So let me understand this. This is gas mostly hydrogen that appears to be coming in from two directions, mostly bottom left and top right. Presumably this happened after the big bang and inflationary period where the universe expanded out in all directions. As the gas collides near the bottom center it rebounds back out to top left and right causing more collisions. Stars form and then galaxies which then cause a cluster. But if there was a single big bang , what caused the two original gas clouds to turn around and move toward each other? Seems their gravity would be about the same. Probably a closed universe where expansion was overcome by collapse. But today astronomers say the universe isn't closed but expansion is speeding up?

You're not looking at the entire universe here, just one tiny, tiny region of it. This region isn't large enough to see cosmological expansion at all. Of course, the whole region is being carried by expansion, but we don't see that because our frame of reference is set to the center of the developing cluster. So all we're seeing here are local gravitational interactions. The Big Bang left the gas distribution inhomogeneous, and so clumps are attracted to each other gravitationally, which is what's causing the collisions.

• The Hubble Big Bang expansion is tracked by the evolving scale shown at the upper left.
  
  Top to bottom distance at end of clip ~ 2.85 Mpc versus the diameter of observable universe ~ 28,500 Mpc.
  
  Dark energy expansion is not supposed to have an effect on self contained entities such as galaxy clusters.

Not to mention that Dark Matter filaments help matter contract and clump along the lines of those filaments at the same time as the expansion of the universe goes on as a whole... inward falling gas and matter should be relatively along those lines, if not absolutely because of momentum...what amazes me is the "splay" of all those stars as galaxies appear to be ripped apart by near collisions and such. I assume a bagillion years from now it is all one bugigantic galaxy...

It is a bit like a fetus... structure forms...even as it grows....

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Boomer12k wrote: ↑Tue Feb 26, 2019 11:25 pm
It is a bit like a fetus... structure forms...even as it grows....

• And a bit like red sprites: https://apod.nasa.gov/apod/ap141013.html
  
  http://asterisk.apod.com/viewtopic.php? ... 99#p290134

Thank you for the music, Glad it is not some horribly repetitive industrial music like so many Youtubers use.