ITN: Spiral Arms & Star Motion Proved

[CraigS]

Now here's an interesting news item:

Milky Way stars move in mysterious ways

Rather than moving in circles around the center of the Milky Way, all the stars in our Galaxy are travelling along different paths, moving away from the Galactic center.
…
This strange behavior may be due to perturbation caused by the central bar and spiral arms of our Galaxy, forcing stars to leave their normal circular course and take an outward path.
…
For over twenty years, scientists believed that the potential impact of these density waves on stellar velocities in the Milky Way was insignificant in comparison with the circular motion of the stars in the galactic disk. This belief has now been blatantly proved wrong by an international team
...
To reach this conclusion, the team systematically analyzed the velocities of over two hundred thousand stars located within a radius of a little over six thousand light years around the Sun. Using data from the major star survey RAVE (RAdial Velocity Experiment) collected since 2003 by the Australian Astronomical Observatory's Schmidt telescope, they were able to measure for the first time the radial velocities of hundreds of thousands of stars and determine whether they were moving towards or away from us.
…
The researchers were thus able to ascertain that the average speed of stars towards the exterior of the Galaxy increases with their distance from the Sun in the direction of the Galactic center

The RAVE website and papers are here

This stellar motion stuff just gets more and more perplexing !
They're saying that the combined effect of the central bar and the spiral arms could explain the motion (as close as 6K lyrs from the Sun) !! Fascinating !! More reading to do on this one !!

Cheers

[Robh (Rob)]

Very interesting!
Wouldn't that indicate an increasing number of stars flung from the galaxy over time? How does this affect the view that dark matter keeps stars in sync with the galaxy rotation?
Also, wouldn't the rotation of the galaxy slow down as stars move further out?

Regards, Rob

[CraigS]

G'Day Rob;

Ah .. goodness me !!

Originally Posted by Robh

Very interesting!
Wouldn't that indicate an increasing number of stars flung from the galaxy over time?

Yes it would seem so ! It may also tend to suggest that the stars actually originated from the centre of the galaxy and this would explain the older ones being at the outer edges (??)

Originally Posted by Robh

How does this affect the view that dark matter keeps stars in sync with the galaxy rotation?

Yep. Good question. Dark matter is theoretical … these guys are astronomers (and they're practical types ! )

Originally Posted by Robh

Also, wouldn't the rotation of the galaxy slow down as stars move further out?

yes .. I think they've only measured the rotation velocities .. I haven't checked to see if they've modelled any of this in rotation curves. (This step involves modelling the mass distribution .. they may be leaving that up to someone else, in which case, it'll be interesting to see where this one goes !)

I'll snoop around to see if they've produced any theory updates from the observations.

Cheers

[Outbackmanyep]

I think those questions could be directed to Fred Watson when he comes onto ABC Radio! Give it a shot you might get an answer from one of the astronomers involved in this work!

[CraigS]

Rob and OBMYep;

I'm grateful for OBMYep putting us onto the work that Bryan Gaensler, Ray Norrs and Enno Middelberg are doing, on the unknown origin of large scale magnetism, which may end up going some of the way towards helping to describe (or disprove) the origins of some of the forces in Galaxy spiral shapes.

This thread seems to be a good one to post the following supplementary info on (just as a reminder for us all).

Here's what one of his PhD students has to say about the status of it all.

Here's a one page summary for the POSSUM proposal (not yet approved).

I'm really looking forward to seeing more from these guys in the future.

Cheers
PS: Not that I'm turning into an Alex or anything !!

[xelasnave]

I drove up from Sydney last night (12hrs) and had plenty of time to think about the things I think about and had raised this very question in a short conversation I had with myself.

Does this mean spiral galaxies are unwinding in effect??? the reasonable but unsupported presumption would be that all matter is gradually being sucked into the massive black hole at the galactic center however the observation must indicate the opposite...
How interesting I think I will go over it again still very tired.

alex

[mswhin63 (Malcolm)]

Actually past belief is the galaxaies are being held together and that matter according to gravitational theory should be holding the spiral arms together. This is the primary reason for Dark matter to explain this.

If the galaxies are actually flinging apart then dark Matter can't be holding it toegther.

The recent post of massive number or Red Dwarfs could be slowing this flinging as well.

Could this be the total demise of Dark Matter or will it continue.

Disclaimer just a laugh

[xelasnave]

My view is dark matter is a myth. I subscibe to a view that gravity comes via a universal flow of particles which construct the gravity field of the universe and that gravity does not work by attraction. In a particle push environment there is no need for dark matter to explain why galaxies dont fly apart...and clearly galaxies require an external force to hold them together..I contend that the external force is not dark matter... the more dark matter you add to balance the worse the problem gets ..but my view is unsupported and nothing more than an old mans view on something he knows little about.

alex

[CraigS]

Alex;

It would seem that your particles would be 'dark' .. I mean, we can't see them, can we ?

In another post, it seems that you mentioned that they would fit the Cold Dark Matter category quite nicely. (?)

Cheers

[mswhin63 (Malcolm)]

I was looking for this post again, I am listening to podcasts "Astronomy 161" and went through Gravitation theory. Basically it is more an introduction and the talks are about rotating bodies planet around star, etc etc.

In responce to this thread I was wondering that solar systems are quite possibly rotating with other solar systems within a spiral arms of a galaxy and that gravitation theory would suggest that the multiple solar system could be rotating around each other creating their own stabilising orbit. This could hold the spiral arms together to a degree.

This post suggests that the spiral arms are flying apart but to what degree and what concentrations is unknown to me.

The question in my mind is has anyone tested the rotation of different solar systems or stars to see whether they are holding together within spiral arms or as we have only just touch the discovery of planetary discoveries there is not enough data to work with. Again this could reject the theory of dark matter which is the primary reason for holding of outer spiral arms.

Although this thread suggests proven flying apart the spiral arms, I always though they actually measured the spiral arms were being held together. So there is obvious discrepencies somewhere between this report and other reports too.

I apologise for the wording of this as I am writing this in response to my conversational mental thoughts. I am considering re-sitting year 12 english again.

[xelasnave]

Originally Posted by CraigS

Alex;

It would seem that your particles would be 'dark' .. I mean, we can't see them, can we ?

In another post, it seems that you mentioned that they would fit the Cold Dark Matter category quite nicely. (?)

Cheers

Craig you make a fast assumption in assuming particles are dark on the basis that we can not see them.

Dark implies an absence of colour on the one hand but it may simply be the intensity of a particular colour... they may be a light green for example as opposed to a dark green. Yellow would be good and it is mostly light...

I find it strange that when ever physics is met with a problem the word dark seems to be used as a suitable qualification..we have dark matter, dark energy, I read about "dark" accelerators and there is more I cant recall... dark means "we have no idea really and are happy to indulge in mystery etc.."and I suppose such an approach has given us the term black hole..and as a friend of mine once said... why cant black holes be white as we cant see them so who knows what the colour is...black is an absence of all colour but dark seems to attach to things that are mysterious and has no reference to colour intensity ...mmm ... we need a grant I think.

One thing is for sure if we consider the E=MC^2 thing and theoretically convert all the energy running around in a void or other parts of space seemingly devoid of matter and attach a "mass" to the energy we find well yes we would appear to have a great deal of matter but I doubt if it is "dark" as being energetic one could think such matter may be more gaily adorned.

I admit that there must be more matter out there than we (I) figure... Craig I do believe you may have it all worked out and so I can hand over running the Universe to you..if that is ok that is.

alex

[CraigS]

Originally Posted by mswhin63

I was looking for this post again, I am listening to podcasts "Astronomy 161" and went through Gravitation theory. Basically it is more an introduction and the talks are about rotating bodies planet around star, etc etc.

In responce to this thread I was wondering that solar systems are quite possibly rotating with other solar systems within a spiral arms of a galaxy and that gravitation theory would suggest that the multiple solar system could be rotating around each other creating their own stabilising orbit. This could hold the spiral arms together to a degree.

This post suggests that the spiral arms are flying apart but to what degree and what concentrations is unknown to me.

The question in my mind is has anyone tested the rotation of different solar systems or stars to see whether they are holding together within spiral arms or as we have only just touch the discovery of planetary discoveries there is not enough data to work with. Again this could reject the theory of dark matter which is the primary reason for holding of outer spiral arms.

Although this thread suggests proven flying apart the spiral arms, I always though they actually measured the spiral arms were being held together. So there is obvious discrepencies somewhere between this report and other reports too.

I apologise for the wording of this as I am writing this in response to my conversational mental thoughts. I am considering re-sitting year 12 english again.

Hi Malcolm;

You might like to check out this thread which I started a few months ago. (My post #35 summarises most of the content in the thread if you don't want to wade your way through the whole discussion). There's a lot of interesting info which Carl and I wrangled through, about density waves and the theories about why spiral arms are spiral shaped.

Its a very interesting topic.

I'm in a bit of a hurry tonight, but I'm happy to talk more about it when I get the chance (maybe tomorrow).

Cheers & Rgds

[xelasnave]

Hi Malcolm
I think the most exciting thing we can do is to find such a question as you raise. Your interest in such matters will be stimulated and until you find an answer that is satisfying such question will remain and guide your reading perhaps.
Given the fact that gravity travels at the speed of light any gravity message will take some 150,000 years for stars on the outer edges to be received one edge to the other (assuming you think gravity must have a messenger particle) now this means that if one relies on attraction within the galaxy stuff should fly apart..it seems not to..at least in a radical fashion... I think dark energy is also enlisted to explain why this will not happen..it presents as an external force not only to explain an expanding universe but to explain why galaxies simply dont fly apart. With the information you provide it seems its time for speculation as to what the heck is happening and irrespective of coming up with the right or wrong answer it is the consideration of the matter that is important.

alex

[CraigS]

Originally Posted by xelasnave

Dark implies an absence of colour on the one hand but it may simply be the intensity of a particular colour... they may be a light green for example as opposed to a dark green. Yellow would be good and it is mostly light…

Dark matter is matter that is inferred to exist from gravitational effects on visible matter and background radiation, but is undetectable by emitted or scattered electromagnetic radiation. From my knowledge thus far of your theory, your particles would seem to fit that category. Do they or don't they?

I find it strange that when ever physics is met with a problem the word dark seems to be used as a suitable qualification..we have dark matter, dark energy, I read about "dark" accelerators and there is more I cant recall... dark means "we have no idea really and are happy to indulge in mystery etc.."and I suppose such an approach has given us the term black hole..and as a friend of mine once said... why cant black holes be white as we cant see them so who knows what the colour is...black is an absence of all colour but dark seems to attach to things that are mysterious and has no reference to colour intensity ...mmm ... we need a grant I think.

Try studying up on 'Black Body Spectrum'. It has a very specific profile which clearly defines what 'Black' means in Science.
White holes are also theorised to exist.

One thing is for sure if we consider the E=MC^2 thing and theoretically convert all the energy running around in a void or other parts of space seemingly devoid of matter and attach a "mass" to the energy we find well yes we would appear to have a great deal of matter but I doubt if it is "dark" as being energetic one could think such matter may be more gaily adorned.

See the definitions above.

I admit that there must be more matter out there than we (I) figure... Craig I do believe you may have it all worked out and so I can hand over running the Universe to you..if that is ok that is.

C'mon Alex .. I was thinking we should enter you into the hunt for Dark Matter !
After all, you have a vested interest in all of this, no ?

Cheers

[mswhin63 (Malcolm)]

Originally Posted by xelasnave

Hi Malcolm
I think the most exciting thing we can do is to find such a question as you raise. Your interest in such matters will be stimulated and until you find an answer that is satisfying such question will remain and guide your reading perhaps.
Given the fact that gravity travels at the speed of light any gravity message will take some 150,000 years for stars on the outer edges to be received one edge to the other (assuming you think gravity must have a messenger particle) now this means that if one relies on attraction within the galaxy stuff should fly apart..it seems not to..at least in a radical fashion... I think dark energy is also enlisted to explain why this will not happen..it presents as an external force not only to explain an expanding universe but to explain why galaxies simply dont fly apart. With the information you provide it seems its time for speculation as to what the heck is happening and irrespective of coming up with the right or wrong answer it is the consideration of the matter that is important.

alex

I wasn't theorising but am quite happy to keep my thoughts as I learn a little more (call it brain stimulation). I think we can safely say that findings are changing and that maybe we should looking for mass/matter that is more easily identifiable than the current theory of some invisible mass.

There is about 3 notable thread running at the moment including massive more suns than predicted (I am not good at tracking down posts), that could bind a relationship in the whole concept of matter in the galaxies and their affects.

Craig I understand the thread no problems there he spiral arms are sweeing through and could create turbulence as well that could cause rotations of stars and system all over the place, this in turn could produce gravitational anomolies that are holding the arms together or fly apart.

When dark matter was first theorised, it was deemed a theoritical matter not discovered so was given a name adhoc. I "feel" that time has distorted the meaning and now looking for something specific that may specific properties, yet tripling the number of suns could lead to answering that theory along with load of other unseen objects including light dust. These are object that at the time were not visible matter and now can be seen.

[xelasnave]

Craig you asked .....Dark matter is matter that is inferred to exist from gravitational effects on visible matter and background radiation, but is undetectable by emitted or scattered electromagnetic radiation. From my knowledge thus far of your theory, your particles would seem to fit that category. Do they or don't they?

My ideas are only ideas at most a hypothesis and as such should not be called theory... the major prediction I made (what the Pioneer would do when out of the heliosphere) although correct to this point in time could not be classed as a reliable prediction in so far as I have no math in support... they slowed thats is all... also I have many candidates for the push in a push universe not one specific particle... I entertain the possibility that the push may be from the EMSpectrum but it is speculative.... being part lawyer I am happy to entertain yes they do and not they dont

Try studying up on 'Black Body Spectrum'. It has a very specific profile which clearly defines what 'Black' means in Science.
White holes are also theorised to exist.

I will read it again but say some of what I rant on about has such as a background that I treat with irreverence.
As to white holes I can say my mate will only say that he was right.
Still both are interesting

C'mon Alex .. I was thinking we should enter you into the hunt for Dark Matter !
After all, you have a vested interest in all of this, no ?
Irrespective of the image I present I do find anything upon dark matter interesting..certainly at one stage I thought my approach and dark matter are the same thing but from different approaches .. I rant to find answers and provoke thinking and discussion and confess I hold no firm views upon anything at all...living without belief in anything is difficult but empowering so I doubt that anything presented to me will not be questioned from whatever opposing position I can take...

Anyways I have retired from developing TOE and now interested in things of simple nature..pool playing, guitar and sailing..simple pleasures and personal thinking... after all who gets to see the stars these days with such rainy weather.

alex