James Webb Telescope reveals Milky Way–like galaxies in young universe | Hacker News Reader

James Webb Telescope reveals Milky Way–like galaxies in young universe

phys.org

Can we measure things like metallicity? My impression is that this shows mature looking galaxy structures indicating that those types of structures can form very early, but the stars should be very low metallicity right?

You'd also expect very few rocky planets, but that's firmly beyond the ability of JWST (and maybe anything else) to directly measure.

Good point! It seems that they do not mention metallicity in this paper. However they have spectroscopic redshifts from a previous Hubble Space Telescope (HST) survey [1]. So maybe from that data the metallicity can be estimated.

[1] https://iopscience.iop.org/article/10.3847/0067-0049/225/2/2...

And the paper is here: https://arxiv.org/abs/2210.08658

How do bars channel gas into the galaxy core? I haven't heard of that before.

My understanding is rough, since I’ve only watched a few lectures, but from what I recall:

You essentially get rolls in the plane of the galaxy, which are like giant tube vortexes. The gas preferentially goes along the straw instead of leaving the tube due to magnetic effects of large scale swirling in the galactic plasma.

Sort of like a filament forming in a plasma globe: the plasma preferentially travels along (well, swirls with) the filament.

I thought large-scale plasma astrophysics was considered a crackpot theory. https://en.wikipedia.org/wiki/Plasma_cosmology Interesting that it's now getting some more mainstream attention.

My understanding is there’s something of an ambiguous situation:

Electric/magnetic fields in the galaxy are known to play important roles in its structure; but where the “plasma cosmology” tends to go wrong is asserting that EM is the dominant force that explains the galaxy or larger structures.

Personally, I think this is somewhere we’ll need a unified theory to decide: we’re seeing effects that look like gravity and look like EM, depending on how you squint. Which is unsurprising, as they’re happening around a black hole.

Because Electric Universe drum beaters are crackpots talking about how stars are powered by magical currents rather than fusion and geology is dominated by arc events rather than plate tectonics.

However, Alfvein cosmology does have merits in explaining galactic scale phenomena and solar phenomena certainly have a electrical component (see: huge quantities of charged particles berating Earth at all times).

I'm not an astrophysicist, but I asked one. She mostly talked about the galaxy's potential well, the galactic spin (which is higher at the center), and kinematic interactions between baryons (gas and stars, principally). I mentioned magnetism and she said that it isn't really her field, so she didn't give much comment...

I’m having trouble finding the original talk, but a few related links from a quick Google:

https://news.northwestern.edu/stories/2022/11/the-milky-ways...

https://www.space.com/meerkat-milky-way-mosaic-filaments

https://arxiv.org/pdf/0901.1165.pdf

I would say that for the dynamics of galactic plasma, you can’t ignore any interaction: kinetics, gravity, nor EM. They all interplay, within a system.

I'm afraid that none of that is correct.

When you have a (rotating) bar, the allowed orbits tend to intersect with each other. This has not effect on the stars, since they're so small relative to the space involved that they never collide; but gas clouds are quite large, and they will intersect with each other. The resulting collisions cause them to lose some of their (orbital) energy and sink onto smaller orbits.

If I remember correctly, a second effect is that the collisions tend to cause the gas to concentrate/pile up near the leading edge of the bar, which causes an offset between the mass of the stars (making up the bar) and bulk of the gas; the stars end up pulling on the gas in the direction opposite to the orbital motion, and so the gas loses energy and angular momentum, shifting onto smaller orbits.

It really has nothing to do with magnetic fields: you readily get this effect in hydrodynamical simulations without any magnetism, and most of the gas in the bar region isn't in the form of plasma anyway (it's primarily a mixture of neutral atomic hydrogen and molecular hydrogen).

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