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Why are we so sure that there is a need for dark matter?


Dandav
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7 hours ago, Dandav said:

Let's look at the bulge.

There are millions or even billions of stars over there.

Most of them don't have a circular orbital path.

We can clearly see the un circular path in the S stars motion:

You're not showing bulge objects in your picture. These are stars gravitationally bound to Sgr-A, and there's only perhaps a few hundred of them. There are yes, billions of stars in the bar, but those are not gravitationally bound to Sgr-A any more than are we.

How can you 'clearly' tell that those S stars don't have circular motion? A circle seen from any angle other than from a point on its axis will appear to be an ellipse, so it isn't immediately clear at all. Can you answer that?

As for the rest of the post, it is just full of wrong assertions and questions whose answer I cannot explain to you any more than I can to a squirrel.  The dynamics of stars in a galaxy is complicated and doesn't lend itself to trivial answers and polite little formulas. You don't want the real answers anyway since you deny every one of them.

We seem to have stopped making progress, so I'm probably gone after this. Go talk to JeffreysTubes8 who seems more on your level.

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5 hours ago, Halc said:

How can you 'clearly' tell that those S stars don't have circular motion? A circle seen from any angle other than from a point on its axis will appear to be an ellipse, so it isn't immediately clear at all. Can you answer that?

Please look at the following image:

Galactic_centre_orbits.svg

Based on the location of Sgr-A we can clearly understand that most of those S stars has none circular motion with reference to that SMBH. Not even the closest S2 star.

5 hours ago, Halc said:

You're not showing bulge objects in your picture. These are stars gravitationally bound to Sgr-A, and there's only perhaps a few hundred of them. There are yes, billions of stars in the bar, but those are not gravitationally bound to Sgr-A any more than are we.

Yes, I fully agree.

5 hours ago, Halc said:

You don't want the real answers anyway since you deny every one of them.

That is incorrect.

I fully respect your answers. However, you ignore the key idea in my message:

13 hours ago, Dandav said:

Can you please offer even one Bar galaxy in the entire universe without ring and its spiral arms?

You Know that there is no possibility to get a Bar without the Ring and its spiral arm.

Based on the observation, the Bar is there ONLY when the ring and its spiral arms are there.

Hence, the observation proves that the bar is there due to the Ring Gravity impact!

How can we ignore the real meaning of that OBSERVATION?

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Let's summarize the key points about the Bar in spiral galaxy:

1. There is no bar if there is no ring and spiral arms.

2. The Bar has a symmetrical shape

So, how the Bar gets its shape?

In order to understand it, please look at the following image of the Earth due to the tidal impact of a satellite:

Field_tidal.svg

So, although there is just one satellite - in one side, Its tidal gravity force push the matter in the earth in both sides and set a symmetrical shape.

The Earth is quite solid object and therefore the impact on its matter due to that satellite (or even a moon) tidal force is quite minor.

How-tidal-bulges-occur_Nick-Lomb.jpg

However, the Bulge in the center of our galaxy isn't solid.

It is made out of millions or billions of stars that orbit somehow in that bulge.

Therefore, without any main external gravity force, there is no tidal force and the bulge would be spherical.

We see many objects that have spherical shape as globular star clusters.

In each globular cluster there are many stars that orbits around each other:

Globular cluster Omega Centauri, captured by Fernando Oliveira de Menezes, São Paul, Brazil.

This cluster isn't affected by any main outwards gravity force and therefore, it keeps its spherical shape.

However, if we would set a massive ring of stars around this globular star cluster, then its tidal force would start to work.

As the cluster is not solid, the tidal force due to the ring would change the spherical shape of the cluster to symmetrical Bar structure.

Hence, I hope that you agree that the bar in spiral galaxy is all about two symmetrical arms that had been pushed outwards from the spherical Bulge due to the tidal force with the ring + spiral arms.

Edited by Dandav
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Before we try to understand how spiral galaxy works, we must understand how the Bar really works.

So, the Bar had been formed by the Ring+ spiral arms Tidal force on the Bulge.

This Tidal force pushed matter/Stars from the spherical bulge into those two symmetrical arms in order to form the Bar shape.

Hence, The Bulge had changed it spherical shape into bar shape due to that tidal force.

Now, let's try to understand the orbital rotation curve:

RotCurve2.gif

https://www.astronomy.ohio-state.edu/thompson.1847/1101/RotCurve2.gif..

We clearly see that up to about 3KPC the orbital velocity is increasing linearity.

Hence, if the orbital velocity at a radius of 1KPC is 80 Km/s than the orbital velocity at 2KPC is exactly 160Km/s

This proves that the stars in the bar are bonded /interacted to the bar by gravity force and increasing their orbital velocity as they are located further away in the Bar.

I would explain the orbital velocity at the spiral arms later on.

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On 12/5/2022 at 6:31 AM, Shustaire said:

I'm going to start here  if you calculate via Newtons gravitational laws. The baryonic mass distribution should give us a Kepler decline in rotation curves. The outer region stars would not rotate at the same rate as the internal region.

 I'm sure you have heard this before. However it has little to do with the BH at the center. If you look at the r^2 relation of [tex] f=\frac{GMm}{r^2}/[tex]you will see the force of gravity will quickly reduce to effectively zero as the radius increases. 

This is also true with the galactic bulge...

 So what matter distribution us required to keep the rotation curves in a non Kepler decline such as we see in spiral galaxies ?

The orbital velocity of any star in the galaxy is based on its local orbital motion + the revolving motion of the Bulge, Bar or spiral arm.

When we look on the motion of nearby stars, we see that each star is moving in a different direction at an average velocity of about 10 Km/s.

TCP_01_15.jpg

That local orbital motion is needed to hold/interact the star to the arm by gravity.

However, when we look from outside, we need to add to this local velocity the orbital motion of the arm

Therefore, when we look at a star that is located at the Bar, we need to add its local velocity in the bar to the revolving motion of the bar.

The local velocity is dictated by newton law and as we already know its contribution for the total velocity is quite neglected.

In order to get better understanding, let me offer the following example:

Let's assume that an observer in space is looking at our planet.

He can only see elephants while the whole planet is transparent for him.

Do you agree that even if the elephants are not moving at all, that observer would see them moving at relatively high speed due to the rotation of the planet.

In the same token when we look at a star in the Bar we actually monitor its local velocity + the bar revolving velocity.

Once we understand that key issue, we can go on and explain the other section of the galaxy.

Edited by Dandav
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Let's summarize the key functionality of the Bar.

1. The Bar had been formed by tidal gravity force of the ring/spiral arms on the Bulge.

2. Due to that tidal force matter and stars from the Bulge had been pushed outwards into the two symmetrical arms that formed the bar. We can clearly see the direction of the tidal forces on the spherical bulge:

Field_tidal.svg

3. All the matter/stars in the Bar had been ejected outwards from the Bulge. It would never come back as long as the tidal force continue to work.

4. Therefore the Bar acts as an output funnel that transfer matter and stars from the bulge into the Ring and Spiral arms. Hence, The Bar is a key element in the transformation from a spherical bulge shape into a disc ring & spiral arms. 

5. We should consider the Bulge + Bar as one object that should be called Bar shape Bulge.

 

Edited by Dandav
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With regards to the Bar funneling of gas and stars.

In the following article our scientists understand that the Bar act as a funnel, but they wish to believe that it funnel matter from the spiral arm into the Bulge:

https://cosmoquest.org/x/2021/05/galactic-bars-may-funnel-material-and-trigger-star-formation/

"In a new study appearing in Astronomy & Astrophysics, researchers led by Eduardo González-Alfonso have switched to using infrared light. What we’re learning now is that a bar can act as a highway to funnel gas and dust from the outer parts of the galaxy into the core, where it can trigger star formation and feed the central supermassive black hole."

But that understanding is just based on a wish.

The tidal gravity force, won't let even one star to move inwards and I have proved it.

Therefore, the Bar can only funnel gas and stars from the Bulge into the Ring / Spiral arms!

Edited by Dandav
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This is the image of the milky way:

https://skyandtelescope.org/astronomy-news/the-milky-ways-new-arm/

 

Milky Way's structure

 

"The Milky Way's basic structure involves two large spiral arms believed to originate at either end of an elongated central bar. "

"A few years ago, Benjamin and others used NASA's Spitzer Space Telescope to deduce that our galaxy really has just two main spiral arms, not four as had been thought. Called the Scutum-Centaurus and Perseus arms, these appear to connect up nicely with the ends of the galaxy's central bar."

So how it works?

The Bar is gravitational arm which acts as a highway to funnel gas, dust and stars from the Bulge into the two main spiral arms.

Any star there sets gravitational interaction with the nearby stars and follow with the outwards stream from the bulge to the spiral arms.

It works as a Cake Icing Piping Cream Pastry Bag

However, instead of delivering cream it delivers Stars, gas and dust from the Bulge into the spiral arms. The thickness of the spiral arm is dictated by the thickness of the edge of the Bar.

In the milky way this thickness/diameter is 3000LY.

Therefore, the bar adds new layer of stars as it revolves and increase the length of the spiral arms from inside.

Hence, the stars in the spiral arms do not need to follow the orbital motion of the bar.

The stars just need to hold each other in the arm by gravity and go with it wherever is goes.

As the gravitational spiral arm is constantly drifting outwards, then at any radius from the center the average velocity of stars is about 220Km/sec.

Therefore, there is no need for dark matter

The gravitational spiral arm is good enough!

 

Edited by Dandav
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I would like to add some more information about the real meaning of gravitational arm:

Our scientists have measured the density of G stars around the Sun.

They have measured 64 G stars at 50LY radius.

Based on that density we can calculate that the estimated G stars per 100LY should be 64 * 2^3 = 512 stars.

Surprisingly, when our scientists have measured the G stars in 100LY around us the have found exactly 512 stars.

That PROVES that the density of stars in our location is exactly 512 per 100LY.

I wonder why our scientists didn't continue and measured the number of stars in 200LY, 500LY and 1000LY in the Orion arm. Please be aware that the thickness of the Orion arm in our location is about 1000LY (and the Sun is located at about 200LY from the side of this arm)

In any case, based on the measured density, we can easily calculate the G stars in the 1000LY sphere (This is the diameter of the Orion arm/pipe):

512 * 10^3 = 512,000 stars.

Now let's think about a 1000LY star cluster with 512,000 that stay somewhere in the open space.

Do we agree that it should have enough gravity force to bond all its stars without any need for central massive object?

I have found the following computer animation, derived from a type of computer code called an N-body simulation, shows 100 identical stars in a time-lapse movie where hundreds of years pass in one second.

http://www.astronet.ru/db/xware/msg/1178657

It is stated:

"The orbits of stars around the cluster are typically not as circular as the orbits of planets in our solar system. Cluster stars frequently fall more directly toward the center and many times trace out unusual and complex loops. The vast space inside a cluster result in stars colliding only rarely. "

If 100 Stars could hold themselves together by gravity then 512,000 stars can also do it.

However, it is important to notice that the orbital motion of the stars in the cluster isn't circular but unusual complex loops.

That can explain the orbital Bobbling motion of the stars near the Sun.

Each star is moving in a different direction but all of them are bonded by gravity force.

Therefore, we can claim that each star in the spiral arm holds itself to the arm by gravity force (while it orbits in a complex loop) and goes with the arm wherever the arm goes.

Hence, do you agree that there is no need for any sort of dark matter to bond the star to its spiral arm?

Edited by Dandav
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How the spiral arms really work?

In the following article it is stated:

https://www.astronomynotes.com/ismnotes/s8.htm

"Galaxies are billions of years old so the spiral pattern must be a long-lasting feature. What maintains the spiral pattern?"

So the key feature of spiral galaxy is that their spiral arms MUST be long-lasting.

Therefore, they can't be something that is created randomly by some sort of random activity as density wave and then break down.

Long lasting means - real structure that holds itself for millions over billions years!!!

Unfortunately, our scientists couldn't solve the enigma of the spiral arms as they have assumed that stars in the spiral arms should maintain their distance from the center  of the galaxy.

That is their ultimate mistake.

Stars in the spiral arms do not care about their distance from the center of the galaxy!

They only need to maintain themselves in the arm by gravity force.

However, as the arm spins, any star that is located farther away from the base of the arm, it facing stronger ejected forces.

It is similar to the Carousell momentum:

מתקן שעשועים (צילום: אינסטגרם\2ncktmy)

 

Therefore, the stars in the spiral arms do not maintain their distance from the center of the galaxy but only maintain their location in the arm.

Let's set the current available data:

1. At our location (8KPC from the center of the galaxy), the thickness of the arm is 1000LY and the G star density is 512 stars per 100LY sphere.

2. At the base (3KPC from the center), the spiral arm is connected to the ring and its thickness is 3000LY. I would assume that the G star density there should be much higher than this 512 per 100LY (however, I couldn't find any data on that.)

3. At the far edge of the spiral arm (12 -15 KPC from the center), the thickness of the arm is just 400LY. I assume that the G star density there must be much lower than 512 per 100LY. 

Based on that data let's verify how spiral arms really works:

We should consider the spiral arm as some sort of elastic cable that is made out of star clusters that are bonded to each other in a long line by gravity force.

Each star cluster holds itself to the one that is closer to the base.

The star cluster at the edge of the arm are facing the strongest ejecting force.

It would be stretched to its maximal gravity bonding force and therefore the thickness of the arm at this far end location is so low (only 400LY) and the density of stars should also be very low.

At some point, the orbital ejecting force would be stronger than the gravity bonding force and that last star cluster would be ejected from the spiral arm.

As it is ejected from the arm it would also be ejected from the galactic disc.

Therefore, any cluster that isn't located directly on the galactic disc couldn't be considered as part of the spiral arm.

At the same time new layer of stars would be added to the base of the spiral arm by the bar as it rotates and increase the arm from inside.

Hence, any star that had started its jury at the base of the spiral arm, would constantly drift outwards and at the end it would be ejected from the edge of the spiral arm.

In this process, the orbital motion of each star would be at kept at about 220 Km/sec while the spiral structure would be a long-lasting feature.

Hence, the life time of stars in the spiral arms is quite limited, while the life time of the spiral arms is unlimited.

Is it clear?

Edited by Dandav
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On 12/12/2022 at 4:34 PM, JeffreysTubes8 said:

What math does Dandav do?

Almost none, which is why perhaps he actually believes the claptrap spewed in the above posts which violates mathematics at every step.

He did manage to notice that 64/50³ yields the same value as 512/100³. Hence the 'almost' in my above statement.

 

"It is mathematics which reveals every genuine truth, for it knows every hidden secret… Whoever then has the effrontery to study physics while neglecting mathematics should know from the start that he will never make his way through the portals of wisdom."

--- Roger Bacon (13th century)

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Dear Halc

Welcome back.

You were missing.

There is no need for complex mathematics to validate my explanation as it is so simple explanation and there is no need for dark matter.

However, as you insist for the math.

Please look at the orbital rotation curve:

image.png.01842fb035eb1a68af5119c8c5354af0.png

Let's start with the bar: 

As I have already explained the velocity of the stars in Bar gravitational arm is based on their local velocity + the velocity of the arm.

The local orbital velocity of the stars = The orbital motion that is needed for the gravity interaction or bonding between the arm to the star and it is quite neglected.

Therefore, the main velocity impact in the bar is due to the orbital motion of the Bar.

Please remember:

P = 2 * 3.14 * R

Hence, as the bar is a linear object than a star at 2R should cross twice the distance as a star at R.

P1 = 2 * 3.14 * R

P2 = 2 * 3.14 * 2R

P2/P1 = 2

Therefore, a star at 2R should move twice faster than a star at R.

Please look at the rotation velocity for the bar.

Do you confirm that the math fully meets the Bar velocity observation?

Once you agree with that, we will move on to the math calculation of the spiral arm.

Edited by Dandav
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12 hours ago, Halc said:

"It is mathematics which reveals every genuine truth, for it knows every hidden secret…

I would like to remind you that with all the complex math that our scientists have used in their mega computation system, they have totally neglected the Bar segment.

Do you confirm that our scientists have just focused on the spiral arms and have no clue why the orbital motion in the bar is increasing linearly?

Edited by Dandav
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Dear Halc

Let me say it clearly.

The Bar is the most important feature in the spiral arm.

In the article It is stated:

NASA - Barred Spiral Galaxies Are Latecomers to the Universe

Bars form when stellar orbits in a spiral galaxy become unstable and deviate from a circular path. "The tiny elongations in the stars' orbits grow and they get locked into place, making a bar," explained team member Bruce Elmegreen of IBM's research Division in Yorktown Heights, N.Y. "The bar becomes even stronger as it locks more and more of these elongated orbits into place. Eventually a high fraction of the stars in the galaxy's inner region join the bar."

Therefore, I have few questions:

1. How could it be that those scientists from Nasa with deep knowledge in science could understand the real meaning of the bar and the real impact of tidal force? 

2. Do you agree that this "tiny elongations in the stars' orbits grow and they get locked into place" is a random process? If so, how could it be that this random process could set a Bar at a size of 3KPC which means triple times the size of the Bulge (1KPC)?

3. Why that random process always sets two symmetrical arms? Why never ever one arm, three or more?

4. Technically, the Bulge itself is the big brother of a globular star cluster. There are millions over billions globular star clusters in the universe. If that kind of process was real, then why we have never ever observed even a bar in any globular cluster in the entire universe?

5. How can you explain the following contradiction:

In one hand it is stated that stars are locked in the Bar: "The bar becomes even stronger as it locks more and more of these elongated orbits into place."

While on the other hand it is stated that the bar transfer gas towards the center: Bars are perhaps one of the most important catalysts for changing a galaxy. They force a large amount of gas towards the galactic center, fueling new star formation, building central bulges of stars, and feeding massive black holes.

So, how stars and gas could be locked in the bar and in the same time the same Bar can transfer the same gas and stars inwards?

6. How they couldn't understand that the Bar is a direct outcome of tidal force due to the ring + spiral arms that are located around the Bar?

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