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Author Topic: Why do Galaxies and Stars rotate?  (Read 25710 times)

Offline thebrain13

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Why do Galaxies and Stars rotate?
« Reply #25 on: 24/01/2007 20:30:57 »
Explain how the virial theorem can increase angular momentum.
 

Offline Mr Andrew

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Why do Galaxies and Stars rotate?
« Reply #26 on: 25/01/2007 16:51:54 »
Well, I don't know what the virial theorem is but I understand how a very elliptical orbit, which would be elongated so much that most of the star's momentum would be linear, could be made more circular through interactions with nearby stars thus increasing the angular momentum of the star and decreasing its linear momentum (circles are less linear than ellipses...especially elongated ones).  So, we are back again to how all of these stars got their randomly oriented linear momentum which was then converted into their angular momentum.
 

Offline Soul Surfer

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Why do Galaxies and Stars rotate?
« Reply #27 on: 26/01/2007 09:28:36 »
The virial theorem deals with the motion of self gravitating bodies that have elastic collosions a bit like the kinetic theory of gases.

Stars in a galaxy or a star cluster are objects of this type

If you consider the cluster or galsxy to be isolated from any other bodies take out any common motion of the cluster in any direction and look at the motions of the bodies under their mutual gravitation and allow some time for the system to stabilise.  The virial theorem alows you to extimate if the grou is in the first place gravitiationally bound and not falling apart and then assuming that it IS a gravitiationally bound object what its total mass is from the fact that the angular momentum around the centre of gravity of the object must be a clearly defined fraction of the total momentum in the cluster.  It is a very poweful tool from which a grat deal of our understanding of the motions of stars and galaxies originates.
 

Offline ukmicky

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Why do Galaxies and Stars rotate?
« Reply #28 on: 27/01/2007 01:41:20 »
I
  So, we are back again to how all of these stars got their randomly oriented linear momentum which was then converted into their angular momentum.

Here a theory i read a long time ago which i believe was backed up with lots of math.
My explanation maynot be fantastic but here we go.

In the period not long after the big bang and before the galaxies had formed the universe was populated with vast regions of gas. Eventually the gas came together through mutual attraction forming super dense regions,millions of years later these regions became so dense that the very first stars were formed and as these first stars  moved through space they feed on more and more gas and become supergiants. They eventually got so big that there lives were cut short and went supernovae collapsing into the first blackholes.

At this time space was still mainly full of gas and moving through space these blackholes feed on the surrounding gas and occasionally merging together until they formed the  super massive  blackholes which now reside in the center of all the galaxies.(not proved yet}

Moving through space these blackholes continued feeding on the surrounding gas and as they feed the resulting energy release from the quasar which formed put energy into the remaining dust and gas producing motion ,As the moving gas and dust was captured by the blackhole and it fell towards the blackhole angular momentum occurred which after a few billions eventually formed what we call a galaxy.

Dark matter also plays its part by preventing galaxies from flying apart but as no one knows how and when it was formed is hard to say what part it played in the formation process.

So basically the theory is that galaxies got the majority of there Angular momentum from the energy released through the quasars of the very first blackholes which formed before the galaxies.
« Last Edit: 27/01/2007 01:59:19 by ukmicky »
 

Offline thebrain13

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Why do Galaxies and Stars rotate?
« Reply #29 on: 27/01/2007 04:02:54 »
How can galaxies get angular momentum from quasars?
 

Offline ukmicky

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« Reply #30 on: 27/01/2007 15:52:10 »
Well i presume the huge amount of energy released by a quazar would have been released into the dense gas and dust cloud surrounding the blackhole, the gas  would have heated up producing motion within the cloud and triggering star birth.

If something with momentum is captured by the gravitational pull of a star or blackhole ,its either going to pulled straight in or its momentum will cause it to orbit.

I WILL SEE IF I CAN FIND AN INDEPTH ARTICLE ON IT ,BUT IT MAY TAKE A WHILE I'M GOING BACK 7 OR 8 YEARS
Sorry didnt mean to shout :)
« Last Edit: 27/01/2007 16:13:29 by ukmicky »
 

Offline ukmicky

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Why do Galaxies and Stars rotate?
« Reply #31 on: 27/01/2007 16:45:44 »
Here's one, not the one i'm looking for and it only gives a basic run down, i will keep looking.

http://www.bbc.co.uk/science/horizon/2000/massivebholes_transcript.shtml
« Last Edit: 27/01/2007 16:50:31 by ukmicky »
 

Offline jason2679302

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« Reply #32 on: 31/01/2007 04:34:18 »
May I ask a simple question here, WHY DOES ANYONE CARE HOW THE UNIVERSE FORMED...WHAT WE NEED TO KNOW IS HOW IT WILL END?  And LEARNING HOW IT FORMED I GUARANTEE YOU WONT FIND ANY ANSWER WHATSOEVER AS TO WHAT OUR PARTICULAR GALAXY IS GOING TO DO IN THE FUTURE.  IT SEEMS TO ME ON THE OUTSIDE THAT EVERY SINGLE GALAXY IS DIFFERENT...THEREFORE WE WILL NEVER UNDERSTAND IN ANYONES LIFETIME EVER ON HOW TO CONTROL OR ADAPT TO SUCH A SEQUENCE OF EVENTS.  OTHER THAN A STARTREK SHIP FOR EACH AND EVERYONE OF US :)  SO WHY AREN"T YOU GUYS WORKING ON BUILDING SPACESHIPS THE WHOLE WORLD FOR THAT MATTER INSTEAD OF WASTING BILLIONS OF DOLLARS...ON GUESSING WHAT IS OUT THERE??  BECAUSE IT SEEMS TO ME THE ONLY THING THAT WOULD EVER BE PERMANENT IS SPACE ITSELF...sorry for the caps!
 

Offline jason2679302

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« Reply #33 on: 31/01/2007 04:39:05 »
WHEN I THINK DEEPLY ABOUT THE ENTIRE PROCESS IT JUST BLOWS MY MIND BEYOND BELIEF TO SPECULATE ON HOW ANYTHING EXISTS AND WHERE IN THE HECK AND WHEN DID IT ALL HAPPEN...ITS JUST TOO BIZZZARE FOR THE HUMAN MIND TO HANDLE...WE CAN TAKE APART EVERY PIECE FOR A TRILLION YEARS AND WE WILL NEVER FIND THE TRUE ANSWER...THAT MY FRIENDS IS AMAZING!!!
 

Offline Soul Surfer

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Why do Galaxies and Stars rotate?
« Reply #34 on: 31/01/2007 11:42:55 »
Brain13   Maybe this will help consider a large explosion as we see it in the air on earth.  You will see expanding clouds of gas and dust looking a bit like a cauliflower if you look at the separate blobs you will see that they are rotating some outwards and some inwards this represents chunks of more coherent angular momentum that have come from the generalised expansion energy of the explosion. now consider this extended to a vast supernova explosion that expands for millions of years to push lumps of gas around that eventually collapse into stars and galaxies.  It is this turbulent motion on a large scale that ensures that there is plenty of angular momentum in the clouds.
« Last Edit: 31/01/2007 11:45:24 by Soul Surfer »
 

Offline thebrain13

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« Reply #35 on: 31/01/2007 23:38:48 »
If you look at the total angular momentum of the entire system before a nuclear explosion goes off, and then compare it to the angular momentum afterwords, you would find that it was exactly the same. No known experiment can change angular momentum as a whole. It's true that you can say part of the mushroom cloud now contains angular momentum, but the opposite value is going to be precisely equally opposite and will conteract it somewhere else in the cloud.

A supernova, as grand, powerfull, and large as it is, can't create one bit of angular momentum inside a galaxy unless it radiates mass and an opposite value of angular momentum relative to the galaxy, in one coherent opposite direction, and we no longer recognize that isolated mass and energy as part of the galaxy anymore.
 

Offline Soul Surfer

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Why do Galaxies and Stars rotate?
« Reply #36 on: 01/02/2007 00:03:50 »
I agree that the total angular momentum has not changed but what has happened is that parts of the cloud have more angular momentum in one direction and parts have more angular momentum in a different direction etc  the whole lot adds up to zero but given time there are galaxy sized chunks with excesses in one direction or another. 
 

Offline thebrain13

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« Reply #37 on: 06/02/2007 00:47:59 »
How could those form?
 

Offline Soul Surfer

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« Reply #38 on: 09/02/2007 17:09:09 »
I have not forgotten this question but am searching for a good proof that will convince you that the amount of rotation observed in stars and galaxies is perfectly natural and arises out of their formation and does not need any influence outside of the universe setting them rotating.  This influence (if it existed) would have to act on individual stars and galaxies because the axes and directions of rotation appear to be random on a large scale.
 

Offline thebrain13

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« Reply #39 on: 14/02/2007 03:12:18 »
Well soul surfer, if there is an answer to this question, and I really dont think there is, I hope you find it. Cause I have a theory for how massive more dense objects will tend to rotate faster over time, so if you do find an answer then my theory is not necessary, but I'll be thankfull because you'll save me some trouble down the road.
 

Offline Soul Surfer

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« Reply #40 on: 14/02/2007 09:52:23 »
In some ways my suggestions related to spiral galaxies suggest this  that is the energy on the supernova explosions is more likely to create more explosions where it is propagating in one direction rather than its revese.  what is your idea?

I am busy tryng to work out the statistical deviation of a large cold cloud of gas from zero angular momentum assuming that it was uniform and well mixed and seeing what the statistics of the rotation would be once it had contracted enough to form a star
 

Offline thebrain13

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« Reply #41 on: 14/02/2007 18:18:34 »
Believe me when I say, I want to explain this to you, but it really is not in my best interest. Remember, im only 19, all the physics I know I taught myself, I completely blew off school. And I think about relativity all day. And for all my hard work I have created a very grand theory. So I refuse to explain my unique thinking, because if someone were to steal it, my life would officially be over.
 

Offline ukmicky

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Why do Galaxies and Stars rotate?
« Reply #42 on: 15/02/2007 03:30:17 »
Quote
A supernova, as grand, powerfull, and large as it is, can't create one bit of angular momentum inside a galaxy unless it radiates mass and an opposite value of angular momentum relative to the galaxy.

I don't see how you can use that example and I can't see how you or anyone can say for sure that a galaxies angular momentum must always stay the same because Angular momentum is just rotational kinetic energy and energy can be put into or removed from any system which is not closed and i don't see how anyone can say a galaxy is a closed system when we have no real idea what is surrounding them.

To understands the angular momentum of a galaxy and therefore see if its closed and why they have angular momentum you need to firstly measure the kinetic angular momentum of a galaxy which is impossible as you need to know what to measure which we donít because itís impossible to tell for sure what has had an influence on the galaxy or what may still be influencing it.  What if some outside force like dark matter or energy is exerting an influence on the galaxies over millions of years and is slowing them down decreasing their rotational energy or even speeding them up increasing their rotational energy.  Dark matter could be flowing through space and have its own kinetic energy which could be robbed or added to as it encircles the galaxies.

As you know the stars around the outer most parts of most galaxies are not under the gravitational influence of anything in the centre of the galaxy therefore there Angular momentum does not have anything to do with them orbiting anything in the centre. It's the dark matter outside galaxies which channels and turns their kinetic energy into rotational angular momentum.

In other words it's this dark matter which prevents and stops rapidly rotating galaxies from flying apart, it holds the stars within galaxies when by rights they should fly off in to space due to the angular momentum of the galaxy. So should we see these outer most stars circular path which is due to the surrounding dark matter as part of the angular momentum of the visible galaxy or the visible galaxy and the dark matter which we can't see. If it's the latter where is edge of the galaxy at the edge of the visible regions or at the edge of the dark matter surrounding the galaxy, how big is the pot, where is the outer most edge of the dark matter, its invisible.

How is it possible to know or measure a galaxies total kinetic angular momentum without firstly knowing what the properties of the dark matter which is holding the galaxies together is or what actual influence it has on the stars it's keeping within the galaxy.   
They also believe that dark matter makes up the vast majority of the mass of the universe and was around from the very beginning,  And as the galaxies nowadays are orbiting within areas of dark matter its probably safe to assume that the fledgling galaxies were forming within very dense regions of dark matter much denser than today.
 
Is it possible that in the beginning the dark matter compressed these fledgling galaxies helping the dense star forming regions to form, in turn this help form the first super massive stars, when these first stars died and went super nova the surrounding dark matter which could be flowing then contained and channeled the resulting blast of energy contained within the gas and dust cloud  thrown out and forced it into a  circular motion giving rise the angular momentum we see today.

but hey i could be wrong,but it sounds plausible
« Last Edit: 15/02/2007 04:50:20 by ukmicky »
 

Offline Soul Surfer

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Why do Galaxies and Stars rotate?
« Reply #43 on: 15/02/2007 19:54:29 »
thebrain13 please let me caution you about putting all your faith in one idea it could all end in tears however good it is.  I speak as a retired expert who has made a good living and is enjoying a good retirement by creating and selling good ideas over many years.  In my book, ideas are tuppence a ton and I give them away freely.  It is the application of the idea where all the work goes.

If you want to talk privately send me a personal message or an email.  I promise to treat anything you say in the strictest confidence and have no desire or need to pinch anyone else's ideas. however I do also promise tho comment honesly on my understanding of the idea.
 

Offline Soul Surfer

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« Reply #44 on: 15/02/2007 20:23:39 »
ukmicky.  Your reply seems to have several physical flaws in it and as you claim to be a moderator I am a bit cautious in case I have misunderstood what you are trying to say.

Galaxies and even star clusters within galaxies can be considered as substantially independent systems.  without this a lot of the ensemble analysis of astronomers would not work and many critical inferences could not be made.  Any independent gravitating system subject to virial analysis would in my books constitute a substantially closed system.

Our understanding and analysis of dark matter comes from the analysis of the gravitational dynamics of stars in galaxies and seems to me completely at odds with your second paragraph.

While it is true that the motions of stars in a galaxy are not dominated by a single central gravitating body like planets in the solar system  they are mainly subject to the collective force of all the stars gas and dark matter inside the sphere centered on the centre of the galaxy and their location with respect to the centre.  Except in the case of extremely rare close approaches between stars.

The properties of dark matter is that it is only subject to gravity so its affects can be analysed even though its "temperature" (the average velocities of the elements of which it is made up) May not be well known.

My understanding of the word compressed means pushing from the outside and gravity (and hence dark matter)cannot do this it can only "suck from the inside" it is clear that the dark matter is not very cold or it would rapidly congregate at the centres of galaxies making their velocity profiles much more like solar systems (and less detectable)
« Last Edit: 15/02/2007 20:26:04 by Soul Surfer »
 

Offline ukmicky

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Why do Galaxies and Stars rotate?
« Reply #45 on: 15/02/2007 21:05:25 »
Ian
oh well scatch that one [:I], I was actually waiting for you to come along and find fault with it but hey  it sounded good to me.


By the way if i get something wrong then Ive got no problem with you or anyone voicing your opinion no matter what you wish to say. :)
« Last Edit: 15/02/2007 21:15:09 by ukmicky »
 

Offline thebrain13

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« Reply #46 on: 15/02/2007 22:20:38 »
Soul Surfer, I will explain it to you, just give me time, my theory is a little ambitious. I'm working everything over in my mind right now, I feel like I've reached a plateau, and there are not many loose ends or problems like there always were in the past. I plan on making a return to a labratory at michigan state soon. Basically what Ive done is Ive created another branch of relativity. and with that I think I can explain an enormous amount. I explain how gravity and strong force are electrical. I explain why the universe is accelerating. I explain the "dark energy force" And of course, I explain how galaxies stars planets protons spin the way they do. Thats just the most noteworthy. And I did it in a fashion that would make einstein proud. I figure with the pure simplicity of my solutions, and the pure magnitude of things I can explain with it, I have to be right.

Lets just hope I'm not some crazy person with an ego problem.
 

Offline that mad man

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Why do Galaxies and Stars rotate?
« Reply #47 on: 15/02/2007 23:05:02 »
First I have to say I don't know why.

One thing that has interested me before though is the way in which most particles seem to spiral out, as seen in bubble chamber pictures.

Could it be due to particle physics, an electron knocked out of a hydrogen atom would spiral inwards losing energy as it does so. It also seems that at the centre of these Galaxies there is little or no gravity if I understand ukmicky right.
 
If the Galaxies matter consisted mainly of one type then would the above on a massive scale cause momentum?

edit: I originally put exotic particles!

"B"


« Last Edit: 15/02/2007 23:13:07 by that mad man »
 

Offline Soul Surfer

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« Reply #48 on: 16/02/2007 09:02:18 »
You've got a lot of ideas wrong madman.  firstly bubble chamber pictures and particle physics have nothing to do with the gravitational effects we see in galaxies. The particles spiral because the chambers are designed to have a big magnetic field that makes moving charged particles bend so that their energies can be measured.

Secondly there is a strongly gravitating core at the centre of most galaxies and globular clusters.  This is probably a single black hole or a group of blackholes orbiting each other.  Although this is not strong enough to account for the motions of all the stars without proposing dark matter or modified Newtonian dynamics (MOND)it is strong enough to play a significant part in the dynamics of the galaxy.
 

Offline that mad man

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« Reply #49 on: 16/02/2007 17:33:53 »
Thanks for explaining gravity and the bubble chamber Soul Surfer, happy to be corrected :)

I didn't realise it was to keep the particles in, I thought they spiralled naturally when knocked out of orbit.


TMM
 


 

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