Solar Neighborhood Enigma

[David Levy]

Please see the following presentation at pg 15

http://www.ifa.hawaii.edu/~barnes/ast110/MilkyWay.pdf

There is an image of the galactic rotation random vectors in the nearby Solar Neighborhood.

It is stated:

"Most stars near the Sun have random velocities of a few tens of km/sec. These stars orbit the galactic center at ~230 km/sec."

Let' assume that few tens of km/sec is about 25 to 50.

Hence, each star in the Solar Neighborhood, has a random velocity of about 10% to 20% with related to the orbit velocity.

In this image, we see that those random velocity vectors are pointing all directions. Up, down, left and right.

Therefore, if those stars will maintain their momentum and their velocity vectors, they will be ejected from the spiral arm in about one million year. Each one will be ejected at a random direction from the arm.

Hence, there is no smooth flow of stars (in and out) as we would expect based on the density wave theory.

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

" Lin and Shu proposed in 1964 that the arms were not material in nature, but instead made up of areas of greater density, similar to a traffic jam on a highway.[3] The cars move through the traffic jam: the density of cars increases in the middle of it. The traffic jam itself, however, does not move (or not a great deal, in comparison to the cars)"

The image of the galactic rotation random vectors might contradicts this description.

However, the most interesting velocity vectors are those which are pointing up or down with regards to the disc plan of the galaxy.

Any star which has an up (or down) velocity vector will be ejected from the disc plan itself.

In any case, most of the stars in the solar Neighborhood have some horizontally component in their velocity vectors. Therefore, by keeping their momentum, those stars should be ejected from the disc plan in less than few million years.

In the same token, few million years ago, those stars could have been over or below the disc plan of the spiral galaxy.

So, how could it be???

[Acme]

...However, the most interesting velocity vectors are those which are pointing up or down with regards to the disc plane of the galaxy.

Any star which has an up (or down) velocity vector will be ejected from the disc plane itself....

No. Our solar system and [presumably] other stars oscillate with respect to the galactic plane, moving 'above' and then back 'below'.

[bolding mine]

The Sun's motion perpendicular to the galactic plane

The period and amplitude of the Sun's motion perpendicular to the galactic plane are important parameters in some explanations of the terrestrial mass extinctions and cratering records15. Here we have calculated the range of periods and vertical excursions that are consistent with the distributions of tracer stars in the Galaxy and have also evaluated the probable phase jitter in the solar period. We find acceptable half-periods for the vertical oscillation that range from 26 to 37 Myr (including the range of periods that have been inferred from the terrestrial records on mass extinctions and on cratering), maximum heights above the plane from 49 to 93 pc, and an average phase jitter per half-period of the order of 69%. The largest uncertainty in all these calculations is caused by the unknown distribution of the unseen mass that must be postulated to explain the distribution of observed stars67. For all the models we consider, the most recent passage of the Sun through the galactic plane occurred in the past 3 Myr provided only that the present position of the Sun is between 0 and 20 pc above the plane. We extend the argument of Thaddeus and Chanan8 to show that the apparent periodicity in the mass extinction and cratering records cannot be caused by an population of objects (observed or unobserved) that contributes a major fraction of the total mass density at the solar vicinity.

[Sensei]

 

Therefore, if those stars will maintain their momentum and their velocity vectors, they will be ejected from the spiral arm in about one million year. Each one will be ejected at a random direction from the arm.

 

Star needs to have galaxy escape velocity or more to escape galaxy.

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

 

https://www.newscientist.com/article/dn24249-stars-escape-velocity-shows-how-to-exit-the-milky-way/

[David Levy]

No. Our solar system and [presumably] other stars oscillate with respect to the galactic plane, moving 'above' and then back 'below'.
[bolding mine]
The Sun's motion perpendicular to the galactic plane

 

Thanks

 

So, our solar system and [presumably] other stars oscillate with respect to the galactic plane, moving 'above' and then back 'below'.

 

But why?

What kind of power is needed to change the momentum (and the velocity vector) of each individual star?

Why it Is working only for above and below the galactic plane? What about right or left momentum?

What is the source for this power?

Is it gravity force or some dark power?

Edited September 22, 2015 by David Levy

[Sensei]

Stars attract other stars in their neighborhood. The most visible example is binary star system. They're rotating around their common center of mass.

[David Levy]

Stars attract other stars in their neighborhood. The most visible example is binary star system.

 

If Stars attract other stars in their neighborhood, than by definition it is gravity force.

Binary star system is excellent example for gravity force.

Therefore, can we assume that all stars in the nearby Solar Neighborhood attract each other by gravity force?

Hence, do you agree that the gravity force is the power which is needed to change the momentum of each individual star in the system?

 

 

They're rotating around their common center of mass.

 

Where is the common mass location of all the stars in the nearby Solar Neighborhood?

Edited September 22, 2015 by David Levy

[Acme]

 

So, our solar system and [presumably] other stars oscillate with respect to the galactic plane, moving 'above' and then back 'below'.

Thanks.

But why? What kind of power is needed to change the momentum (and the velocity vector) of each individual star

Why it Is working only for above and below the galactic plane? What about right or left momentum? What is the source for this power?

Is it gravity force or some dark power?

 

Yes, gravity. Dark matter is hypothesized because of its gravitational effects.

 

If Stars attract other stars in their neighborhood, than by definition it is gravity force. Binary star system is excellent example for gravity force.

Therefore, can we assume that all stars in the nearby Solar Neighborhood attract each other by gravity force?

Yes.

 

Hence, do you agree that the gravity force is the power which is needed to change the momentum of each individual star in the system?

Yes.

 

Where is the common mass location of all the stars in the nearby Solar Neighborhood?

You would have to be precise about 'nearby' to answer that.

 

Here's an article about our local neighborhood.

The Galactic Environment of the Sun

[David Levy]

 

Yes, gravity. Dark matter is hypothesized because of its gravitational effects.

 

Thanks

Please see the spiral arm structure figure in the following tutorial by University of California, San Diego. (Just below the Multiwavelength Milky Way figure).

http://casswww.ucsd.edu/archive/public/tutorial/mw.html

There is high concentration of stars near the sun and especially in the orion-Ceganus arm.

I assume that this concentration of star should be the base for the gravity force as stars attract other stars in thier neighborhood. (As stated by Sensei)

 

Stars attract other stars in their neighborhood.

 

Hence, the question is as follow:

If that gravity force is good enough to holds the star from going too high or too low from the concentration of those stars in the arm, than can we assume that it also should hold it from moving too left or too right (from the concentration)?

In other words, assuming that what we see in that figure is correct and the concentration of stars is located in the arm, can we claim that the stars must stay in the arm? (not too high, not too low, not too right and not too left).

[Mordred]

Not necessarily, stars do move into an out of spiral arms. Higher concentrations of mass certainly inhibit the tendency. However stars are not the only sources of mass. You also have mass due to plasma and the dark matter halo.

 

The other aspect is not everything moves due to a force at the same rate.

 

Remember f=ma, so larger mass objects will accelerate slower than smaller mass objects. Particles will obviously gain greater acceleration than stars.

 

Hence density waves and the traffic jam analogy

 

 

The reason the spiral arms are brighter isn't necessarily due to a greater number of stars within the arm. It's due to a higher concentration of plasma causing reflective and refraction of the light emitted by those stars.

 

A good example is take a flashlight and blow smoke through the beam. Which is more visible? The region with no smoke or the region with smoke?

 

The density wave causes higher concentrations of plasma, which aid star formation. However the wave moves faster than the stars, so it leaves those stars behind. Catching up to previously created stars.

Edited September 24, 2015 by Mordred

[David Levy]

Thanks for the explanation.

I have a simple question:

What is the real source for that gravity which keeps the stars from moving above or below the disc plane?

Based on your message, it might be the "mass due to plasma and the dark matter halo".

 

However stars are not the only sources of mass. You also have mass due to plasma and the dark matter halo.

 

However, The halo (or the plasma?) aren't located on the galactic plane. Therefore, we actually get a negative gravity force which should pull out the stars from the disc plan.

Based on my understanding, this isn't the case.

Therefore, the gravity must come from the galactic plane itself. I assume that the nearby stars or what's call "Solar Neighborhood" should be the main source for this gravity force.

Please let me know if you agree with that.

Edited September 24, 2015 by David Levy

[Mordred]

The only way to explain this is look at the Earth moon system. Ask yourself why does the Earth have a greater influence upon the moon's orbit than the Sun? Localized gravity can be greater than the global gravitational influence.

 

Same with stars local clusters can overpower the outer regional influences. Creating locally bound systems whose collective mass is greater. Again due to f=ma they will accelerate at a slower rate than smaller clusters.

The dark matter halo surrounds the galaxy, however the greater concentration of plasma is on the plain.

However that plasma wasn't ALWAYS on the plane. Prior to becoming a spiral disk galaxy, the plasma was a halo cloud. Forming older stars outside of the disk.

[David Levy]

Well, I'm not sure that I fully understand your reply.

Do you claim that mass in the hallo, (or any mass outside the disc plane) can set a gravity force which keeps the stars at the disc plane?

How could it be?

The example of Earth and moon is excellent as it proves that the nearby gravity is much stronger than far end forces.

Therefore, the solar neighborhood mass should have the maximum gravity influence on the sun.

Why don't you agree with that?

Edited September 24, 2015 by David Levy

[Mordred]

Well, I'm not sure that I fully understand your reply.

Do you claim that mass in the hallo, (or any mass outside the disc plane) can set a gravity force which keeps the stars at the disc plane?

How could it be?

The example of Earth and moon is excellent as it proves that the nearby gravity is much stronger than far end forces.

Therefore, the solar neighborhood mass should have the maximum gravity influence on the sun.

Why don't you agree with that?

As to the first question Why does the disk exist? All the mass started as a cloud yet later on forms a disk. The answer is rotation.

 

Your understanding of the Earth/moon system is accurate.

 

What I'm trying to get you to consider is that our galaxy started as a cloud, due to rotation flattens into a disk. The plasma flattens first. (Lighter material). However stars formed while the galaxy was a halo cloud. Not all those older stars have migrated to the disk. The same thing happens to the spiral arms. The stars cannot keep up with the plasma. Hence older stars are typically outside the arms and newer stars forming in the arms.

When you look at where stars are currently you also need to consider where were they formed and the galaxy dynamics at the time of their formation.

( this includes the available composition of plasma)

For example the majority of red dwarf stars we can't see. They are too dim. What is their distribution?

"formation timescales to be placed upon the structures within the Milky Way, namely the Galactic halo and Galactic disk."

 

https://en.m.wikipedia.org/wiki/Red_dwarf

[David Levy]

Thanks

However, at this phase we do not discuss about the creation.

Please try to focus just on the following basic mechanism:

1. I have started this tread by asking about the power which is needed to hold the stars in the galactic plane.

The answer was – Gravity.

So, do you agree that gravity is the requested power? If no, please explain why it is not gravity.

2. I have asked - what is the source for this gravity?

The answer was – nearby stars. (The example of Earth Noon confirms this answer).

So, do you agree that the nearby stars generate the max impact on the gravity? If no, please elaborate.

Edited September 24, 2015 by David Levy

[imatfaal]

!

Moderator Note

 

David Levy

 

I am pretty sure we have already closed your threads comprising arguments from misunderstanding purporting to cast doubt on the existence of dark matter. Please make sure that this does not head the same way.

 

No need to respond to this moderation - report the post if you feel it is unfair

 

[ACG52]

 

 

I have started this tread by asking about the power which is needed to hold the stars in the galactic plane.

Nothing is needed to hold stars in the galactic plane. If their orbit lies within the plane, that is where they stay, unless there's some force acting upon them.

[Mordred]

ACG52 answered the first. As to the second the correct answer is ALL mass contributors of which Stars is just one. Source. Plasma which the stars are made up of is another. Their movement and gravitational influence combined contribute to how galaxies develop into into disks.

 

 

Think about it. How do stars form? They form from plasma. So in order to form a star there must be sufficient plasma. I'm not positive on the exact % of mass the plasma is currently. Though it would have been higher in the past.

 

This is why galaxy rotation curves are based on mass density, not star distribution.

 

( if you want to understand current star distribution, you need to understand the contribution due to plasma). Dark matter doesn't contribute to why the disk is flat. It does affect rotation curves though.

 

Pop 1 stars are found typically in the disk. Population 2 stars are in random eccentric orbits in the bulge and halo. The categories are seperated by the elements that went into their formation. Hydrogen and helium is primary in pop 2 stars. Elements above helium are considered metals and are part of the pop 1 stars. Insofar as pop 1 stars have a higher Abundance of metals.

 

Another aspect is the newer stars have the highest abundance of metals and reside closer to the galactic plane than older pop 1 stars with less metal abundance.

Edited September 24, 2015 by Mordred

[David Levy]

Nothing is needed to hold stars in the galactic plane. If their orbit lies within the plane, that is where they stay, unless there's some force acting upon them.

 

 

In the article which Acme had pointed:

 

 

Yes, gravity. Dark matter is hypothesized because of its gravitational effects.

Here's an article about our local neighborhood.

The Galactic Environment of the Sun

 

It is stated:

"The sun’s path is inclined about 25 degrees to the plane of the galaxy and is headed toward a region in the constellation of Hercules near its border with Lyra."

Therefore, its orbit doesn't lie perfectly within the disc plane. In other words, the Sun and actually all the nearby stars are moving with some degree to the galactic plane. By keeping this momentum and without an external force, the Sun might disconnect from the disc plane. However, it is also stated:

"The sun oscillates through the plane of the galaxy with an amplitude of about 230 lightyears, crossing the plane every 33 million years."

Therefore, some force is needed to change this momentum and keep the Sun in the galactic plane.

Acme claimed that this force must be gravity as dark matter is hypothesized.

So do you agree that some force is acting upon them? Do you agree that it is gravity force?

Edited September 25, 2015 by David Levy

[Acme]

..."The sun oscillates through the plane of the galaxy with an amplitude of about 230 lightyears, crossing the plane every 33 million years."

Therefore, some force is needed to change this momentum and keep the Sun in the galactic plane.

Acme claimed that this force must be gravity as dark matter is hypothesized.

...

To be clear, my comment on dark matter was a separate response to the last clause in your question "

Is it gravity force or some dark power?". That is to say, I was not saying dark matter keeps the solar system oscillating through the galactic plane; I was only saying that dark matter is hypothesized because of observed large-scale movements for which we do not see enough matter to account for such movements.

To be more clear, I do not suggest dark matter is keeping our solar system near the galactic plane. Moreover, I have never read any such suggestion.

[ACG52]

The oscillation is the orbit. There's nothing keeping the sun in the galactic plane. It's orbit is inclined with respect to the plane just as, for example, Venus having an orbital inclination of 3.9 degrees from the ecliptic.

Edited September 25, 2015 by ACG52

[Acme]

The oscillation is the orbit. There's nothing keeping the sun in the galactic plane.

No, I don't think the oscillation is the orbit. From the paper I cited for David:

However, the suns motion relative to the local stellar neighborhood should not be confused with its movement around the center of the galaxy, since the whole solar neighborhood (including the sun) orbits the galactic center once every 250 million years. ...

The Galactic Environment of the Sun

[David Levy]

To be clear, my comment on dark matter was a separate response to the last clause in your question "

Is it gravity force or some dark power?". That is to say, I was not saying dark matter keeps the solar system oscillating through the galactic plane; I was only saying that dark matter is hypothesized because of observed large-scale movements for which we do not see enough matter to account for such movements.

To be more clear, I do not suggest dark matter is keeping our solar system near the galactic plane. Moreover, I have never read any such suggestion.

 

Thanks for the clarification. Your message with regards to the dark matter was very clear from the beginning.

However, do you still agree that gravity is needed to change the momentum of the sun and keeps it in the galactic plane?

Edited September 25, 2015 by David Levy

[ACG52]

since the whole solar neighborhood (including the sun) orbits the galactic center once every 250 million years. ...

 

Thats the Sun's orbit.

 

http://curious.astro.cornell.edu/about-us/159-our-solar-system/the-sun/the-solar-system/236-are-the-planes-of-solar-systems-aligned-with-the-plane-of-the-galaxy-intermediate

 

Our own solar system is tipped by about 63 degrees with respect to the plane of the galaxy. You can see that on this infrared picture taken by the IRAS satellite. The picture is a little tricky to interpret because, like many maps of the Earth, it's an Aitoff projection, which means that the entire sky has been flattened onto an ellipse. But you should be able to see that the angle between the bright horizontal band (the Milky Way's disk) and the blue haze (dust in the plane of the solar system) crosses at an angle of something like 60 degrees.

[Acme]

Thanks for the clarification. Your message with regards to the dark matter was very clear from the beginning.

However, do you still agree that gravity is needed to change the momentum of the sun and keeps it in the galactic plane?

Yes; gravity keeps the solar system and all stars in the arms near the plane.

 

As pointed out in Sensei's link in post #3.

...

From this survey and a previously published star catalogue, the team selected 90 high-velocity stars whose speeds and positions had been determined most precisely. Some of them are moving at speeds of more than 300 kilometres per second, about one-thousandth of the speed of light.

...

To escape the gravitational clutches of our galaxy, a spaceship would need to zoom out of our solar system and hit 537 kilometres per second. ...

Stars escape velocity shows how to exit the Milky Way

So, even the fastest moving stars in the Milky Way do not have the velocity to escape the galaxy.

since the whole solar neighborhood (including the sun) orbits the galactic center once every 250 million years. ...

 

Thats the Sun's orbit.

...

Yes. However that is not the oscillation of the solar system through the galactic plane which is what David was asking for clarification on.

[Mordred]

I've seen this come up on other forums. The hypothesis is that a dark matter disk is involved. Also that this passing through the galactic disk also coincides with the extinction of the dinosaurs. Etc etc etc.

 

I've yet to see any strong support of a DM disk, current profiles suggest a halo profile. However that's just a side note as all were interested in is the inclination bobbing action to the galactic disk mass.

 

Try this thought experiment. Start with our solar systems momentum which has an inclination to the galactic plane.

 

As it approaches the galactic plane it will gain momentum.

 

When it crosses the galactic plane it's momentum carries it past the galactic plane. Then the mass tried to overcome that momentum. The result is it starts losing momentum until it starts heading back towards the plane. (Sinusoidal arc). Then when it passes the galactic plane the same process continues.

 

So yes gravity does alter its course both above and below the galactic disk. However we also need to account for how gravity interacts with the solar systems momentum and direction. (Conservation of energy/momentum)

 

That being said theoretically the sinusoidal behavior should gradually decrease in amplitude and the solar systems movement will become more and more aligned with the galactic disk.

 

How long that will take? No idea without more accurate data and records of decrease in amplitude per cycle.