All galaxies rotate at the same rate

ack

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bonzo75

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Was this measured by speedNic
 

still-one

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Rotate around what ?
 

NorthStar

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https://physics.stackexchange.com/questions/129429/what-does-a-galaxy-orbit

https://www.spaceanswers.com/astronomy/why-do-galaxies-spin/

"It is said that everything spins in the Universe – from galaxies to stars to planets. But why do galaxies rotate?

In the early stages of the Universe, clouds of gas came together to form the stars. These stars were then gravitationally attracted to each other to create gigantic clusters of stars enshrouded in clouds of gas. Eventually these groupings of stars come together through the attraction of gravity and together they start to spin around a common centre of mass. Picking up speed, the rotation squashes the clusters of stars flat forming a disk with a bulge at the centre.

This spinning of galaxies continues even after their formation. Our Milky Way galaxy is one of these spinning structures and its entire disc of stars, gas and dust is rotating at around 168 miles per second. Due to our Galaxy’s rotation, our Solar System appears to orbit the galaxy every 225 million years – the last time we were in the same place in our orbit, dinosaurs were just starting to appear on the Earth. All galaxies spin whatever their type or size."
 

Empirical Audio

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Fascinating. Did you also know that there is a black hole at the center of every galaxy? Even our own Milky Way?
 

still-one

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I presumed that everyone was aware of this ;)

No one had yet identified where this "center of mass" is located are supposedly rotating around. In fact from what I have read the universe has no direction.
 

NorthStar

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? https://science.nasa.gov/astrophysi...raordinarily-diverse-conditions-of-the-cosmos

"Observations with the Hubble Space Telescope and other observatories showed that the universe is expanding at an ever-increasing rate, implying that some day - in the very distant future - anyone looking at the night sky would see only our Galaxy and its stars. The billions of other galaxies will have receded beyond detection by these future observers. The origin of the force that is pushing the universe apart is a mystery, and astronomers refer to it simply as "dark energy". This new, unknown component, which comprises ~68% of the matter-energy content of the universe, will determine the ultimate fate of all. Determining the nature of dark energy, its possible history over cosmic time, is perhaps the most important quest of astronomy for the next decade and lies at the intersection of cosmology, astrophysics, and fundamental physics."
___

There is no direction, the universe expands infinitely in all directions. And there is no center.

https://www.space.com/25673-universe-expansion-real-time-cosmology.html
http://math.ucr.edu/home/baez/physics/Relativity/GR/centre.html
___

¤ https://www.spaceanswers.com/deep-space/is-there-a-centre-of-the-universe/
 
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astrotoy

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The expansion of the universe is a separate issue from the internal motions of galaxies. They are more like large solar systems, which are not themselves expanding, but are moving away from other galaxies (actually other clusters of galaxies). For example, the solar system is not expanding - the earth is not moving farther away from the sun. Similarly the solar system is not moving farther away from the center of the Milky Way.

For each galaxy, there is a center of the galaxy, just like the center of the solar system is the Sun. Very interesting if all galaxies at their boundaries have the same rotational speed. However, the little movie is not correct. A galaxy is not a solid body rotator, like a record or CD. Look at the article from Wiki on the rotation curves of galaxies. If the galaxy rotated as a solid body, then the rotation curve, which measures the speed vs. distance from the center, would be a straight line. At the distance of the solar system, the galaxy takes about 250 million years to orbit around its center. For a long time it was assumed that most of the mass of the galaxy was concentrated at or near the center of the galaxy (that is the implication of the density of starlight toward the center.) However, it was determined, by measuring the speed of the stars and the gas between the stars that there must be a huge amount of material within galaxies that cannot be accounted for by the stars or gas. This was because, instead of the speed of stars and gas farther away from the center slowing down, like planets farther from the sun, they are actually speeding up. This unseen matter is called dark matter, and has been calculated to make up most of the mass of a galaxy. Given their rotation curves, galaxies would fly apart without this dark matter holding them together. The fact that we can date the age of galaxies by the age of their oldest stars, means they have been stable for many billions of years and so must have something holding them together.

https://en.wikipedia.org/wiki/Galaxy_rotation_curve

Larry, your astronomer friend
 
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the sound of Tao

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Thanks Larry, I love astronomy and indeed all science when it is being so illuminating and pure and objective. Ovserving the nature of the galaxy is somehow very numinous and special. Hard to explain why it seems so grand and almost mystical. Astronomy seems almost the most spiritual of all the sciences. Perhaps it’s the scale of it all. Much appreciated.
 

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