Science stories of the week

Pinball1970 said:
on that note....this time spiral galaxy formation.


phys.org

Scientists spot more Milky Way-like galaxies in early universe, advancing our understanding of how galaxies were formed

University of Missouri scientists are peering into the past and uncovering new clues about the early universe. Since light takes a long time to travel through space, they are now able to see how galaxies looked billions of years ago.
phys.org phys.org
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What causes spiral galaxies to maintain their “structure”? Gravity of its stars? Dark matter?
 
wegs said:
What causes spiral galaxies to maintain their “structure”? Gravity of its stars? Dark matter?
Click to expand...
Whoohoo, that'a tough one.

From Wiki:https://en.wikipedia.org/wiki/Spiral_galaxy

The pioneer of studies of the rotation of the Galaxy and the formation of the spiral arms was Bertil Lindblad in 1925. He realized that the idea of stars arranged permanently in a spiral shape was untenable. Since the angular speed of rotation of the galactic disk varies with distance from the centre of the galaxy (via a standard solar system type of gravitational model), a radial arm (like a spoke) would quickly become curved as the galaxy rotates. The arm would, after a few galactic rotations, become increasingly curved and wind around the galaxy ever tighter. This is called the winding problem. Measurements in the late 1960s showed that the orbital velocity of stars in spiral galaxies with respect to their distance from the galactic center is indeed higher than expected from Newtonian dynamics but still cannot explain the stability of the spiral structure.

The article goes on to explain, but it's bloody complicated to understand. I've read it 3 times and can't say I've got it yet.
 
exchemist said:
Whoohoo, that'a tough one.

From Wiki:https://en.wikipedia.org/wiki/Spiral_galaxy

The pioneer of studies of the rotation of the Galaxy and the formation of the spiral arms was Bertil Lindblad in 1925. He realized that the idea of stars arranged permanently in a spiral shape was untenable. Since the angular speed of rotation of the galactic disk varies with distance from the centre of the galaxy (via a standard solar system type of gravitational model), a radial arm (like a spoke) would quickly become curved as the galaxy rotates. The arm would, after a few galactic rotations, become increasingly curved and wind around the galaxy ever tighter. This is called the winding problem. Measurements in the late 1960s showed that the orbital velocity of stars in spiral galaxies with respect to their distance from the galactic center is indeed higher than expected from Newtonian dynamics but still cannot explain the stability of the spiral structure.

The article goes on to explain, but it's bloody complicated to understand. I've read it 3 times and can't say I've got it yet.
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I ask because it’s curious to me how spiral galaxies remain spiral galaxies for a billion years. Hmm…

I found this on YouTube in researching a little on the subject. It’s just a cool visual of how these types of galaxies form.

 
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exchemist said:
The article goes on to explain, but it's bloody complicated to understand. I've read it 3 times and can't say I've got it yet.
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I have vague memories of something to do with dynamic density waves in the spiral arm pattern. That is, individual stars actually cycle in and out of the spiral arms over long periods of time. The pattern is always there, but it is not consistently made of the same stars,
 
James R said:
I have vague memories of something to do with dynamic density waves in the spiral arm pattern. That is, individual stars actually cycle in and out of the spiral arms over long periods of time. The pattern is always there, but it is not consistently made of the same stars,
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That's what the Wiki article explains. There is even an animation showing the process. But I still can't quite visualise what is going on.
 
I read somewhere that spiral and vortices are a natural feature of our universe (link to some features below). Galaxies are complicated and come in several shapes. Spherical, spiral, irregular, tubular (images below) As to how they maintain their shape? If that was truly understood there would not be the Kerfuffle regarding flat rotation curves.

Newton does not explain it, Einstein’s GR does not explain it either. Based on the mass we observe (stars, gas) the galaxy should fly apart, there is not enough mass and therefore gravity holding it together.

The outside should be rotating very slowly compared to the inside but it isn’t, the velocity should fall off so the distance velocity relationship should yield a line that falls off also.

It doesn’t, it is more flat, hence flat rotation curve and the need for something there that does not emit or interact with light, Dark matter.


1718282652364.png



bluelabyrinths.com

Why Do Spirals Exist Everywhere in Nature?

Spirals are a common shape found in nature, as well as in sacred architecture. In the natural world, we find spirals in the DNA double helix, sunflowers, the path of draining water, weather pattern…
bluelabyrinths.com bluelabyrinths.com
 
Elliptical galaxies are the most abundant type of galaxies found in the universe but because of their age and dim qualities, they're frequently outshone by younger, brighter collections of stars.

Elliptical galaxies lack the swirling arms of their more well-known siblings, spiral galaxies. Instead, they bear the rounded shape of an ellipse, a stretched-out circle.

More here: https://www.space.com/22395-elliptical-galaxies.html

I'm under the impression that elliptical galaxies can never ''become'' spiral galaxies. But can spiral galaxies become elliptical ones? It sounds like it can only go one way - spiral to elliptical (but it's not a given). I think this has to do with the fundamental differences of how they're both formed and elliptical galaxies contain less gas and older stars.
 
Pinball1970 said:
I read somewhere that spiral and vortices are a natural feature of our universe (link to some features below). Galaxies are complicated and come in several shapes. Spherical, spiral, irregular, tubular (images below) As to how they maintain their shape? If that was truly understood there would not be the Kerfuffle regarding flat rotation curves.

Newton does not explain it, Einstein’s GR does not explain it either. Based on the mass we observe (stars, gas) the galaxy should fly apart, there is not enough mass and therefore gravity holding it together.

The outside should be rotating very slowly compared to the inside but it isn’t, the velocity should fall off so the distance velocity relationship should yield a line that falls off also.

It doesn’t, it is more flat, hence flat rotation curve and the need for something there that does not emit or interact with light, Dark matter.


View attachment 5904



bluelabyrinths.com

Why Do Spirals Exist Everywhere in Nature?

Spirals are a common shape found in nature, as well as in sacred architecture. In the natural world, we find spirals in the DNA double helix, sunflowers, the path of draining water, weather pattern…
bluelabyrinths.com bluelabyrinths.com
Click to expand...
I don't think much of the link. For a start, a helix is quite different from a spiral, yet the article treats the two as if they are the same.
 
exchemist said:
I don't think much of the link. For a start, a helix is quite different from a spiral, yet the article treats the two as if they are the same.
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That is only a small part of my post. I googled "spirals occur naturally in the universe," that is what I got.
There will be better links, the point is they do occur.
The focus was the shape and dynamics that is not yet explained.
Galaxy evolution is pretty complicated and whatever models they had are not explaining these early ones.
 
This occurs very 80 years. https://phys.org/news/2024-09-qa-astronomers-await-year-stellar.html

From the article

"T Coronae Borealis is known as a "recurrent nova" system. As material builds up on the white dwarf it gets hotter and denser until it ignites a thermonuclear explosion. This burns the surface material, making a bright event that can last for weeks to months. This is called a nova."

A previous article also said later August early November, polish your telescope lenses!
 
Pinball1970 said:
This occurs very 80 years. https://phys.org/news/2024-09-qa-astronomers-await-year-stellar.html

From the article

"T Coronae Borealis is known as a "recurrent nova" system. As material builds up on the white dwarf it gets hotter and denser until it ignites a thermonuclear explosion. This burns the surface material, making a bright event that can last for weeks to months. This is called a nova."

A previous article also said later August early November, polish your telescope lenses!
Click to expand...
They've been promising this every two weeks since March.
 
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