David Levy Posted February 26, 2015 Author Posted February 26, 2015 The 'glow' around the Sombrero galaxy is made up of stars but less populated than in the disk. It should be clear that there is no delineated areas absent of stars because it pervades around and throughout the disk. Sombrero Galaxy.JPG Thanks Yes, it is a special galaxy. This galaxy is called Sombrero Galaxy. And this is the only one under this category. Therefore, it is very unique. Please see the following infrared picture: http://en.wikipedia.org/wiki/File:Sombrero_Galaxy_in_infrared_light_(Hubble_Space_Telescope_and_Spitzer_Space_Telescope).jpg Based on its ratio between the mass ring and the center It looks similar (for me) to a ring galaxy http://en.wikipedia.org/wiki/File:Hoag%27s_object.jpg In any case, I have tried to get further information about the spiral arms: http://en.wikipedia.org/wiki/Sombrero_Galaxy It is stated that the "galaxy's most striking feature is the dust lane that crosses in front of the bulge of the galaxy". But, unfortunately, there is no info about the spiral arms and there is no confirmation that there are stars between the arms. It is just stated that: " Additional observations are needed to confirm that the Sombrero galaxy's molecular gas is constrained to the ring." Therefore, I'm not sure that we can get to any real conclusion about the spiral arms…
StringJunky Posted February 26, 2015 Posted February 26, 2015 Thanks Yes, it is a special galaxy. This galaxy is called Sombrero Galaxy. And this is the only one under this category. Therefore, it is very unique. No it isn't. Note: there will be different degrees of halo because we are seeing different ages of them, depending how far we look into space and other factors.
David Levy Posted February 27, 2015 Author Posted February 27, 2015 (edited) Hi Mordred Thanks for the great articles. I couldn't find any approval for the idea that there are stars between the spiral arms. In the contrary, the evidences which are introduced in those articles gave me further confirmation to Newton laws for spiral galaxy. The explanation is as follow: In the articles it is stated that there are several theories for spiral galaxies. Please see: http://www2.lowell.edu/workshops/expdisks2014/presentations/Davis_Poster.pdf "Spiral structure is the most distinctive feature of disk galaxies and yet debate persists about which theory of spiral structure is the correct one." The density wave theory has two camps: "The density wave theory has been studied for several decades now and still has many sup- porters, divided broadly into two camps: those who contend that the spiral pattern is a long-lasting one created by standing waves (the modal theory) and others who regard the pattern as transient (compared to the lifetime of a galaxy), though perpetually recreated as new density wave patterns emerge (the swing amplification theory)." The density wave could be a perfect theory for Sturn ring, but not to spiral galaxy. There is a significant gap between the two structures. In Spiral disc there is a thick disc and thin disc. In Saturn disc there is only thin disc. "The density wave theory has had one outstanding success since its creation, not as applied to galaxies, but in the context of patterns observed in Saturn’s rings. In the limit of a very large central mass and a thin disk, the pitch angle of these density waves, as shown by Shu (1975), depends on the ratio of the disk mass density to the central mass." Some other theories: "Other theories have also been proposed, with one in particular, the Manifold theory, rejecting the density wave concept altogether, in favor of an explanation involving stars in chaotic highly eccentric orbits." However, the following article gives final approval for Newton theory as I have explained in this tread. Please see: http://www.ifa.hawaii.edu/~barnes/ast110/MilkyWay.pdf In pg. 16 there is a diagram of the Stellar Orbits. Disk stars (yellow) – all move in the same direction on roughly circular orbits. Stars in the bulge (red) - and Halo (green) move in fairly random orbits. In pg. 15 it is stated: "Most stars near the Sun have random velocities of a few tens of km/sec." The density wave theory can't offer any explanation for this evidence. However, this is fully aligned with my explanation. I have already divide the spiral galaxy to three sections. (Please see pg. 36 in this thread) "You have to understand correctly the structure of spiral galaxy. In each structure, there are different forces. So, the spiral galaxy is divided into three main sections. -spiral arms section -Center; The area between the supper massive black hole to the first Inwards ring of the spiral arms. (It is called Bulge) -Outwards – The aria from the far end of the spiral arms and outwards. (It is called Hallo)" The gravity force in the spiral arms is much higher than the gravity force in the bulge or in the Halo. I have already explained it in pg 1 of this thread and in my thread about the expected mass of the black hole (pg.7,12,18). http://www.scienceforums.net/topic/87482-milky-way-galaxy-mass-vs-black-hole-mass/ Hence, in the spiral arm section – (Yellow) the gravity force of the spiral arm keeps the stars in the loop. Therefore, each star might have a random velocity, (pg. 15) but it will keep his position in the arm and continue with the same motion direction of the spiral arm. Therefore, the stars will not be ejected from the arm although they have random up and down velocities. However, in the central section – Bulge (Red) and in the outwards section - Hallo (green) of the galaxy, the gravity force is much less than in the spiral arms section. Therefore, the stars are moving in a fairly random orbits. Actually, that by itself proves that there are no stars outside the spiral arms. If there were some stars outside the spiral arms, those stars must lose the gravity force of the arm. Therefore, it is expected that they will have a fairly random orbits (as it is in the Bulge and in the hallo). This is one more confirmation for Newton law in spiral galaxy! Edited February 27, 2015 by David Levy -2
Mordred Posted February 27, 2015 Posted February 27, 2015 Hi Mordred Thanks for the great articles. I couldn't find any approval for the idea that there are stars between the spiral arms. In the contrary, the evidences which are introduced in those articles gave me further confirmation to Newton laws for spiral galaxy. The explanation is as follow: In the articles it is stated that there are several theories for spiral galaxies. Please see: http://www2.lowell.edu/workshops/expdisks2014/presentations/Davis_Poster.pdf "Spiral structure is the most distinctive feature of disk galaxies and yet debate persists about which theory of spiral structure is the correct one." The density wave theory has two camps: "The density wave theory has been studied for several decades now and still has many sup- porters, divided broadly into two camps: those who contend that the spiral pattern is a long-lasting one created by standing waves (the modal theory) and others who regard the pattern as transient (compared to the lifetime of a galaxy), though perpetually recreated as new density wave patterns emerge (the swing amplification theory)." The density wave could be a perfect theory for Sturn ring, but not to spiral galaxy. There is a significant gap between the two structures. In Spiral disc there is a thick disc and thin disc. In Saturn disc there is only thin disc. "The density wave theory has had one outstanding success since its creation, not as applied to galaxies, but in the context of patterns observed in Saturns rings. In the limit of a very large central mass and a thin disk, the pitch angle of these density waves, as shown by Shu (1975), depends on the ratio of the disk mass density to the central mass." Some other theories: "Other theories have also been proposed, with one in particular, the Manifold theory, rejecting the density wave concept altogether, in favor of an explanation involving stars in chaotic highly eccentric orbits." However, the following article gives final approval for Newton theory as I have explained in this tread. Please see: http://www.ifa.hawaii.edu/~barnes/ast110/MilkyWay.pdf In pg. 16 there is a diagram of the Stellar Orbits. Disk stars (yellow) all move in the same direction on roughly circular orbits. Stars in the bulge (red) - and Halo (green) move in fairly random orbits. In pg. 15 it is stated: "Most stars near the Sun have random velocities of a few tens of km/sec." The density wave theory can't offer any explanation for this evidence. However, this is fully aligned with my explanation. I have already divide the spiral galaxy to three sections. (Please see pg. 36 in this thread) "You have to understand correctly the structure of spiral galaxy. In each structure, there are different forces. So, the spiral galaxy is divided into three main sections. -spiral arms section -Center; The area between the supper massive black hole to the first Inwards ring of the spiral arms. (It is called Bulge) -Outwards The aria from the far end of the spiral arms and outwards. (It is called Hallo)" The gravity force in the spiral arms is much higher than the gravity force in the bulge or in the Halo. I have already explained it in pg 1 of this thread and in my thread about the expected mass of the black hole (pg.7,12,18). http://www.scienceforums.net/topic/87482-milky-way-galaxy-mass-vs-black-hole-mass/ Hence, in the spiral arm section (Yellow) the gravity force of the spiral arm keeps the stars in the loop. Therefore, each star might have a random velocity, (pg. 15) but it will keep his position in the arm and continue with the same motion direction of the spiral arm. Therefore, the stars will not be ejected from the arm although they have random up and down velocities. However, in the central section Bulge (Red) and in the outwards section - Hallo (green) of the galaxy, the gravity force is much less than in the spiral arms section. Therefore, the stars are moving in a fairly random orbits. Actually, that by itself proves that there are no stars outside the spiral arms. If there were some stars outside the spiral arms, those stars must lose the gravity force of the arm. Therefore, it is expected that they will have a fairly random orbits (as it is in the Bulge and in the hallo). This is one more confirmation for Newton law in spiral galaxy! Did you apply escape velocities as I requested earlier in this thread? Without dark matter the stars in the spiral arms would fly apart. Show this isn't so using your calculations. Those articles are in good agreement with density waves, the points you raised has to do with fine tuning. In any theory there is always competing models. Any good peer reviewed paper does a comparison. Also keep in mind separation distance from the BH the force of gravity is inversely proportional to the separation distance. This in and of itself means that the force of gravity from the bulge reduces the further you get from it. This also means the rotation should slow down the further you get from the bulge. I did not see this analysis in any of your posts. So if you want to convince anyone your going to need to show this is accounted for. PS might help to ask yourself, " why everyone with physics degrees of various levels disagree with your idea, that are involved in this thread ?" Granted not everyone involved in this thread have degrees but several of the posters do. Here follow these steps... http://astro.u-strasbg.fr/~koppen/Haystack/rotation.html
David Levy Posted February 27, 2015 Author Posted February 27, 2015 (edited) Did you apply escape velocities as I requested earlier in this thread? Without dark matter the stars in the spiral arms would fly apart. Show this isn't so using your calculations. I will cover those issues later on. Those articles are in good agreement with density waves, the points you raised has to do with fine tuning. In any theory there is always competing models. Any good peer reviewed paper does a comparison.So, would you kindly explain how the Densitay wave theory covers the evidence in pg. 15 and 16? See: http://www.ifa.hawaii.edu/~barnes/ast110/MilkyWay.pdf This isn't fine tuning. This is a huge gap! Also keep in mind separation distance from the BH the force of gravity is inversely proportional to the separation distance. This in and of itself means that the force of gravity from the bulge reduces the further you get from it. This also means the rotation should slow down the further you get from the bulge. This totally contradicts the observation as we see in pg. 15 and 16. If that was correct than the gravity force in the spiral arm section should be lower than the gravity force in the bulge section. This by itself should lead to fairly random orbits in the spiral arm section. However, that isn't the case. Therefore, the gravity force in the spiral section must be much stronger than the bulge! Somehow, you should explain this phenomenon. Please - don't call it fine tuning. Edited February 27, 2015 by David Levy
Mordred Posted February 27, 2015 Posted February 27, 2015 If you complete the analysis in your post one you should show a "Keplarian decline" in rotation curve. Assuming your sticking to strictly Newtonian. Observations show that Keplarian decline does not conform indicating unaccounted mass. Keplarian decline is not rigid body. Rigid body would have faster velocities as you measure from the center. I will cover those issues later on. So, would you kindly explain how the Densitay wave theory covers the evidence in pg. 15 and 16? See: http://www.ifa.hawaii.edu/~barnes/ast110/MilkyWay.pdf This isn't fine tuning. This is a huge gap! This totally contradicts the observation as we see in pg. 15 and 16. If that was correct than the gravity force in the spiral arm section should be lower than the gravity force in the bulge section. This by itself should lead to fairly random orbits in the spiral arm section. However, that isn't the case. Therefore, the gravity force in the spiral section must be much stronger than the bulge! Somehow, you should explain this phenomenon. Please - don't call it fine tuning. I did its called dark matter which estimates place as 10* the mass of baryonic matter. (Stars etc) This is what we've been trying to get you to see throughout this thread. Now look at the Kepler curve as opposed to the galactic rotation curve on this page. http://en.m.wikipedia.org/wiki/Galaxy_rotation_curve Here is the commonly used power law profiles for the distribution of influence DM on the Milky way. There are of course alternative power law profiles. http://en.m.wikipedia.org/wiki/Navarro-Frenk-White_profile http://arxiv.org/abs/1304.0425 2
David Levy Posted February 27, 2015 Author Posted February 27, 2015 (edited) I did its called dark matter which estimates place as 10* the mass of baryonic matter. (Stars etc) This is what we've been trying to get you to see throughout this thread. Before digging in the dark matter issue, and based on the diagram in pg. 15 and 16; Please let me know if you agree or disagree with the following statements: -The gravity force in the spiral arm section should be maximal due to the evidence that all stars move in the same direction on roughly circular orbits. (Agree or disagree) - The gravity force in the Halo and bulge is minimal as the stars move in fairly random orbits (Agree or disagree) - The density wave theory and the dark matter do not give real explanation for this phenomenon. (Agree or disagree) If you disagree, please explain why. Edited February 27, 2015 by David Levy
Mordred Posted February 28, 2015 Posted February 28, 2015 (edited) Here lets do this. First off Keplarian orbits assume a point like mass, we know this doesn't work well for galaxies. So lets step it up a bit. First off we want a formula that includes the mass at every point as you increase in radius. So lets use one. Let's start with [latex]v = \sqrt{\frac{G M}{R}}[/latex] The above is velocity of a point mass. Now we don't want just stars we need to include all particles. They all add mass so we use density profiles. However we also want a formula that has in increasing mass as you increase the distance. [latex]v_r=\sqrt{\frac{G M_r}{R}}[/latex] However this leads to the Keplarian decline. We included all the visible mass. http://en.m.wikipedia.org/wiki/Galaxy_rotation_curve In other words the white visible line in the image, on this page, the top line is the measured rotation curve. The Kepler law that applies is his third law. With the latter formula it is still applicable. However the above is suitable for test Particles at a given radius. Test particles add no gravitational influence. Remember f=ma? Well the consequences of that formula means lighter particles will have a higher velocity than heavier particles. So stars will have a slower velocity than dust. Hrrm could this be why we have density waves???. I'll let you think about that after all the water in your sink draining is an accurate example. The force is due to vacuum pressure aka drain. The fluid approximation between water and gas uses the same relations mathematically. aka hydrodynamic rules. Now given this does that answer your above questions? The latter formula covers all the mass at a given radius. (Except dark matter) (Key note I intentionally used the simpler rotation curve formulas, most employ [latex]\rho[/latex] energy/mass density. I provided numerous links that reflect that Edited February 28, 2015 by Mordred
David Levy Posted February 28, 2015 Author Posted February 28, 2015 (edited) Now given this does that answer your above questions? No! Why is it so difficult for you to reply: agree or disagree? I have asked a simple question: How the science can justify the evidence which we see in pg 15 and 16? Why are you using formulas in order to avoid direct answer? Somehow, we must prove what we see. We shouldn't fit the universe to our theories; We must fit our theories to the universe! So would you kindly explain how those formulas, D.M., Density wave or any other theory fits to what we see in pg. 15 and 16? Later on we will discuss about all the other subjects. Edited February 28, 2015 by David Levy
Mordred Posted February 28, 2015 Posted February 28, 2015 Oh here is an important side note. Another reason for density waves is that gravity is NOT instantly felt. Newtons laws assumes it is. Relativity teaches us that gravity is limitted to c. Hence the further the particle is from a mass source. The longer it takes to react to a change in gravity. No! Why is it so difficult for you to reply: agree or disagree? I have asked a simple question: How the science can justify the evidence which we see in pg 15 and 16? Why are you using formulas in order to avoid direct answer? Somehow, we must prove what we see. So would you kindly explain how those formulas, D.M., Density wave or any other theory fits to what we see? Why do you refuse to accept your wrong? I used Newtons laws to answer your questions. How many more articles and posters does it take to make you see your errors? You never once applied f=ma to the plasma as opposed to stars. Of course the gas moves faster than the stars would. Why can't you see that simple a formula in terms of the wave density? Which would travel faster? The test Particles ,then the lighter elements to the heavier metals, finally the stars Come on open your eyes a wee bit, I'm supplying professional peer reviewed references, to your unsupported model. Here is some more http://www.google.ca/url?sa=t&source=web&cd=3&ved=0CCMQFjAC&url=http%3A%2F%2Farxiv.org%2Fpdf%2F1310.7189&rct=j&q=density%20wave%20galaxy%20measurements%20pdf&ei=dlbxVNqTE8uvyASPjICABg&usg=AFQjCNH2AbT1qzjh_ufC1vAr59c8T4-ECQ&sig2=DNZ_m_3MtaPdoyQchOQYpQ Here is an excellent 116 page slide show. One line is of I interest "Different waves travel at different velocities" http://www.google.ca/url?sa=t&source=web&cd=73&ved=0CCUQFjACOEY&url=http%3A%2F%2Fobswww.unige.ch%2Flastro%2Fconferences%2Fsf2013%2Fpdf%2FPart-3-ISM.pdf&ei=LljxVMbKLoOVyASdxoD4AQ&usg=AFQjCNHV5ndJQFJAnbnb0LO2mC7_tlYfWg&sig2=vtaGeRJ5u0n7sBoQay6J1Q Ie there are more measured waves than just the spiral arms. You requested we cover DM later so my response was specifically not including such 1
David Levy Posted February 28, 2015 Author Posted February 28, 2015 Come on open your eyes a wee bit, I'm supplying professional peer reviewed references, to your unsupported model. Well, it is clear that that you have decided to ignore my question. You are supplying professional peer reviewed references, to avoid evidence which contradicts the current theory. It is not my unsupported model. It is evidence in an article which you have pointed out! Why do you prefer to fit the universe to your theories instead of the other way? Please, try to give a direct answer to my simple question. Please… -1
Mordred Posted February 28, 2015 Posted February 28, 2015 Except as a side note Well, it is clear that that you have decided to ignore my question. You are supplying professional peer reviewed references, to avoid evidence which contradicts the current theory. It is not my unsupported model. It is evidence in an article which you have pointed out! Why do you prefer to fit the universe to your theories instead of the other way? Please, try to give a direct answer to my simple question. Please To be honestly I don't know how simpler I can explain it. The answer to page 17 is DARK MATTER. It accounts for 80% the mass influence You cannot explain it using Newtons laws without fudging those laws like MOND does. These are not my theories, these are the theories every Astro physicist learns. These theories are designed to fit observational evidence. Dark matter went through over 70 years of argument on its need in regard to galaxy rotation curves. Far more knowledgable people than anyone on this entire forum have tried to prove dark matter wrong. Guess what the evidence still supports it.
David Levy Posted February 28, 2015 Author Posted February 28, 2015 (edited) Except as a side note To be honestly I don't know how simpler I can explain it. The answer to page 17 is DARK MATTER. It accounts for 80% the mass influence You cannot explain it using Newtons laws without fudging those laws like MOND does. These are not my theories, these are the theories every Astro physicist learns. These theories are designed to fit observational evidence. Dark matter went through over 70 years of argument on its need in regard to galaxy rotation curves. Far more knowledgable people than anyone on this entire forum have tried to prove dark matter wrong. Guess what the evidence still supports it. Thanks! I do appreciate your answer. So, Dark matter should be the answer to the evidence. However, if it is dark matter, it should have the same effect in each section of the spiral galaxy. Never the less, this isn't the case. In the spiral arm section all stars move in the same direction on roughly circular orbits. While in the Halo and bulge the stars move in fairly random orbits So, how could it be that we see different orbits cycles at each spiral galaxy section? Hence, if Newton law isn't relevant, how can we explain this issue? Edited February 28, 2015 by David Levy
Strange Posted February 28, 2015 Posted February 28, 2015 I couldn't find any approval for the idea that there are stars between the spiral arms. How about: "There are many stars that are also in-between the spiral arms, but they tend to be the dimmer stars (G, K, M-type stars). Long-lived stars will move in and out of the spiral arms as they orbit the galaxy." http://www.astronomynotes.com/ismnotes/s8.htm Or: "It should be emphasized that there are almost as many stars between the spiral arms as in the spiral arms." http://www.atlasoftheuniverse.com/milkyway.html Or: "The apparent voids between spiral arms are actually full of dimmer, redder, and less massive stars like Sol." http://www.solstation.com/x-objects/spi-disk.htm Or: "The density of stars between the spiral arms is about the same as it is along the spiral arms." https://books.google.co.uk/books?id=zoZLBAAAQBAJ&lpg=PA65&ots=3pRpF_hA6k&dq=stars%20between%20the%20spiral%20arms&pg=PA65#v=onepage&q=stars%20between%20the%20spiral%20arms OK. Your turn to provide some evidence that there are no stars between the arms. And note that neither "I don't believe it"nor "it doesn't look like it" count as evidence. 1
StringJunky Posted February 28, 2015 Posted February 28, 2015 (edited) How about: "There are many stars that are also in-between the spiral arms, but they tend to be the dimmer stars (G, K, M-type stars). Long-lived stars will move in and out of the spiral arms as they orbit the galaxy." http://www.astronomynotes.com/ismnotes/s8.htm Or: "It should be emphasized that there are almost as many stars between the spiral arms as in the spiral arms." http://www.atlasoftheuniverse.com/milkyway.html Or: "The apparent voids between spiral arms are actually full of dimmer, redder, and less massive stars like Sol." http://www.solstation.com/x-objects/spi-disk.htm Or: "The density of stars between the spiral arms is about the same as it is along the spiral arms." https://books.google.co.uk/books?id=zoZLBAAAQBAJ&lpg=PA65&ots=3pRpF_hA6k&dq=stars%20between%20the%20spiral%20arms&pg=PA65#v=onepage&q=stars%20between%20the%20spiral%20arms OK. Your turn to provide some evidence that there are no stars between the arms. And note that neither "I don't believe it"nor "it doesn't look like it" count as evidence. I wondered how many adjacent sun-sized stars might span the diameter of a 50 000LYR galaxy and I got 339 057 572 254 suns. No wonder we can't see them individually in the halo in a picture. Edited February 28, 2015 by StringJunky
Strange Posted February 28, 2015 Posted February 28, 2015 While in the Halo and bulge the stars move in fairly random orbits So, how could it be that we see different orbits cycles at each spiral galaxy section? By "random" I assume you mean that they are not in the same plane as the disk? (Which is obviously so because they are not in the disk.) Why would dark matter be releavnt to that? All it affects is the orbital speed, not the angle of the orbit. Hence, if Newton law isn't relevant, how can we explain this issue? Newton's law obviously IS relevant because it is how we know dark matter exists.
Mordred Posted March 1, 2015 Posted March 1, 2015 Thanks! I do appreciate your answer. So, Dark matter should be the answer to the evidence. However, if it is dark matter, it should have the same effect in each section of the spiral galaxy. Never the less, this isn't the case. In the spiral arm section all stars move in the same direction on roughly circular orbits. While in the Halo and bulge the stars move in fairly random orbits So, how could it be that we see different orbits cycles at each spiral galaxy section? Hence, if Newton law isn't relevant, how can we explain this issue? Ok first off you need to realize, most of the mass influence is DM, not the stars. In actuality the total visible mass is a small % of a spiral galaxies mass profile. The majority of the mass is from dark matter. Also when you get down to it the gas nebulae, in clusters tends to have more mass than the stars being formed in that cluster. Makes sense as the nebulae is where stars are born. Now DM is in a spheroid distribution, with a significant mass influence along the disk including further along the disk than the baryonic matter. It is influenced by gravity, but due to no strong force doesn't clump. Gravity still concentrates it somewhat. Instead of trying to use the formula I posted earlier, we treat the galaxy as an ideal gas with an average density. More accurately mass density. When you include visible matter, dust, plasma and dark matter and energy density. The rotation curve follows a power law distribution. Individual star movements is meaningless, their contributions are negligible. For that matter, all the visible matter's influence is a minor contribution to the rotation curve. The majority of the mass isn't in the visible disk and spiral arms. Its in the dark matter halo that surrounds and encompasses our entire galaxy. Now calculating and testing the mass distribution of DM requires using gravitational lenses and its influence, (indirect detection) as we cannot directly measure it. One of the most accurate density profile power laws to date (afaik) For spiral galaxies is this paper http://arxiv.org/abs/1309.5408 Several of the papers I posted show how to calculate rotation curve velocity including dark matter so that information is already provided.
David Levy Posted March 1, 2015 Author Posted March 1, 2015 Thanks Mordred. I'm not sure that I have fully understood your answer. In one hand you claim that: The majority of the mass isn't in the visible disk and spiral arms. Its in the dark matter halo that surrounds and encompasses our entire galaxy.While in the other hand you calim: Now DM is in a spheroid distribution, with a significant mass influence along the disk including further along the disk than the baryonic matter.How could it be? You have to decide where the majority of the dark mass is located. If it is in the Hallo, then it is expected that the significant mass influence will be in the Hallo of the spiral galaxy. If you prefer a significant influence along the disc, than you have to set the DM in the disk. However, in order to meet the rotation curve, I had an impression, that the dark mass should be in the center of the galaxy. So please advice where shall we set the majority of the DM? Actually, why the DM isn't evenly distributed in the galaxy, in the Universe or even in the solar system? Ok first off you need to realize, most of the mass influence is DM, not the stars. In actuality the total visible mass is a small % of a spiral galaxies mass profile.Hence, theoretically, for each kg of visible mass, there are few kg of DM. Therefore, we should have DM also in the solar system. If so, why it has no influence in our system? Please also remember that in the spiral arm section all stars move in the same direction on roughly circular orbits, while in the Halo and bulge the stars move in fairly random orbits. Do you still estimate that the DM is responsible for it? If so, please explain how it could have different influence on each galaxy section. Please feel free to locate the DM at any location which you like. But somehow we must explain whatever we see.
Strange Posted March 1, 2015 Posted March 1, 2015 In one hand you claim that: While in the other hand you calim: How could it be? You have to decide where the majority of the dark mass is located. Dark matter is distributed roughly spherically around that galaxy with increasing density towards the centre. Mordred did NOT say that there was more dark matter in the disk; he said it had a significant influence on the disk. Actually, why the DM isn't evenly distributed in the galaxy, in the Universe or even in the solar system? Gravity. This causes it to be denser at the centre than at the edges. Hence, theoretically, for each kg of visible mass, there are few kg of DM. Therefore, we should have DM also in the solar system. If so, why it has no influence in our system? DENSITY. I have given you a link to a detailed explanation already. Here it is again: http://cdms.berkeley.edu/Education/DMpages/FAQ/question36.html PLEASE READ THIS BEFORE ASKING THE SAME QUESTION AGAIN. Please also remember that in the spiral arm section all stars move in the same direction on roughly circular orbits, while in the Halo and bulge the stars move in fairly random orbits.Do you still estimate that the DM is responsible for it? If so, please explain how it could have different influence on each galaxy section. It affects orbital velocity in roughly the same way everywhere. Please provide some evidence to support your claim that it has a "different influence on each galaxy section".
David Levy Posted March 1, 2015 Author Posted March 1, 2015 (edited) OK. Your turn to provide some evidence that there are no stars between the arms. And note that neither "I don't believe it"nor "it doesn't look like it" count as evidence. Sorry, you didn't provide even one real evidence in all the articles which you have offered. It is just theoretical overview that there are stars between the arms. You have promised that there is a real observation for this issue. I'm still waiting for this one real observation. However, I have already provided real evidence that there are no stars between the arms. Please see again the random velocities of stars near the Sun – pg 15. http://www.ifa.hawaii.edu/~barnes/ast110/MilkyWay.pdf Without Newton gravity force, there is no real power which should keep them in the arm. Therefore, those stars should continue with these random vector velocities. In this case, after few million years most of the stars should be out of the arm, and in different directions! Therefore, by definition, those stars must set fairly random orbits around the center of the galaxy. However, in pg. 16, it is stated that in the spiral arm section all stars move in the same direction on roughly circular orbits, while in the Halo and bulge the stars move in fairly random orbits. Hence, This is a real proof! Actually our Sun age is a few billion years. Therefore, based on the science approach, it was expected that it should be out of the arm long time ago. So how could it be that we are still in the arm??? Edited March 1, 2015 by David Levy -4
Strange Posted March 1, 2015 Posted March 1, 2015 Sorry, you didn't provide even one real evidence in all the articles which you have offered. It is just theoretical overview that there are stars between the arms. That is just ridiculous. You are claiming that all astronomers are liars. Therefore, those stars should continue with these random vector velocities. In this case, after few million years most of the stars should be out of the arm, and in different directions! Therefore, by definition, those stars must set fairly random orbits around the center of the galaxy. However, in pg. 16, it is stated that in the spiral arm section all stars move in the same direction on roughly circular orbits, while in the Halo and bulge the stars move in fairly random orbits. One problem is that you are relying on a presentation with very brief notes rather than a document (ideally a scientific paper) with detailed information. Page 15 says that the stars near the sun have slightly different velocities (a few tens of km/s). From the diagram, it would appear that these small differences are direction as well as speed. However, it also says that they orbit the galactic centre at 230 km/s. So the stars around the sun all effectively orbit at the same speed. So this tells you little about stars in general and nothing about the presence of stars between the arms. So, every single source confirms that there are stars between the arms. You are unable to provide any references stating that there not stars between the arms. Therefore I think we can safely conclude that there are stars between the arms. Hence, This is a real proof! This is proof that either you don't understand what you read or you are deliberately and dishonestly misrepresenting it. Therefore, based on the science approach, it was expected that it should be out of the arm long time ago. So how could it be that we are still in the arm? It is right on the edge of the arm. Either is is just leaving (again?) or it is just entering (again?).
Mordred Posted March 1, 2015 Posted March 1, 2015 Are you sure our sun was birthed in the arm were currently in?
David Levy Posted March 2, 2015 Author Posted March 2, 2015 (edited) It is right on the edge of the arm. Either is is just leaving (again?) or it is just entering (again?). O.K. The Sun is at the edge of the arm. Based on your reply, It could had been out of the arm in the past, or it should be out of the arm in the future. Page 15 says that the stars near the sun have slightly different velocities (a few tens of km/s). From the diagram, it would appear that these small differences are direction as well as speed. However, it also says that they orbit the galactic centre at 230 km/s. So the stars around the sun all effectively orbit at the same speed. In the same token, near the Sun there are several stars at slightly different velocities (a few tens of km/s) and at different directions. Therefore, some of them could potentially move outside the arm, or just had been entered the arm. Hence, it is expected to see at least few stars outside the arm in the nearby space. However, there are no stars outside the arm near the Sun. Why? As you have already verified, all the stars keeps their average orbits around the galactic centre at 230 km/s. This proves that somehow there is a power which keeps them in the arm. Therefore, it is expected that all the nearby stars must adjust their random velocities. Hence, any star which is moving to the edge of the arm must reverse its direction and come back. There is a proof for that. It is Sirius http://en.wikipedia.org/wiki/Sirius "the Sirius system is one of Earth's near neighbors. Sirius is gradually moving closer to the Solar System" "Sirius, known in ancient Egypt as Sopdet (Greek: Σῶθις Sothis), is recorded in the earliest astronomical records" During this long time it had changed its color several times: (Red, Blue, white..) "However, not all ancient observers saw Sirius as red. The 1st century AD poet Marcus Manilius described it as "sea-blue", as did the 4th century Avienus.[75] It is the standard star for the color white in ancient China, and multiple records from the 2nd century BC up to the 7th century AD all describe Sirius as white in hue." This color change is an evidence that the star is adjusting its direction. In the past it was moving away from the sun and now it is moving closer to the sun. In the future it will reverse again its direction.(again and again). This shows that stars in spiral arms are not just moving randomly. Somehow, there is a power which must keep them in the loop. Edited March 2, 2015 by David Levy
Mordred Posted March 2, 2015 Posted March 2, 2015 (edited) How is this proof? Yeesh your impossible. Believe in whatever pink unicorns you wish. I teach those with a desire to learn not those that ignore. Here this is probably too technical, but lets give it a shot. This extremely large measurement survey, explains regions of hearing, due to the spiral arms, if you look close enough it specifically mentions halo stars, thick and thin disk stars, stars moving in and out of the thick and thin disk. It also goes into EXTREMELY extensive details on velocity variations of stars born at different ages. Meaning they will move and seperate 50 km/s may not seem much at first but if you calculate that over time it's a HUGE variation in orbital velocity. In other words there is no hope they will keep pace with each other let alone all consistently stay with the spiral arms movement. Go ahead try it on a calculator. Take 220 km/s over one galactic year 220 million years. Then do the same for stars moving at say 200 km/s Do it for a range of speeds of different ages let's do a + and minus 50 km/s. If you do this you will see that it is IMPOSSIBLE for the stars to all maintain in the same region. http://www.aanda.org/articles/aa/pdf/2004/18/aa0959.pdf Even a mere 5 or 1 km/s difference in velocity will cause separation PARTICULARLY over 4 billion years...... Or 13 billion which is the estimated age of our galaxy. In order for stars to stay in groups they MUST have nearly EXACT velocities as well as traveling in nearly EXACT orbits of inclination. Here is the main page link on that survey paper. http://www.eso.org/public/news/eso0411/ Let's see 4 billion years *365 days in a year* 24 hours per day* 60 minutes hour* 60 seconds per minute* the difference in the velocity of the two stars compared. Start with a mere 1 km/s difference. Get the point????? Why do they move at different velocities? Conservation of angular momentum AND [latex] force=ma[/latex]. BASIC mathematics. You apply a force of g on a one solar mass star then apply that same force on a 2 solar mass star. THEY WILL have different velocities and THEY WILL seperate over time. Especially over a period of billions of years. I requested you apply f=ma numerous times in this thread for that specific reason. This is also why I specifically stated this formula only applies to test particles. Test particles do not have mass [latex]v_r=\sqrt{\frac{G M_r}{R}}[/latex] "In physical theories, a test particle is an idealized model of an object whose physical properties (usually mass, charge, or size) are assumed to be negligible except for the property being studied, which is considered to be insufficient to alter the behavior of the rest of the system" Edited March 2, 2015 by Mordred
Strange Posted March 2, 2015 Posted March 2, 2015 However, there are no stars outside the arm near the Sun. Instead of repeatedly stating this, please provide some evidence. It is a rule of this forum that you are required to support your claims. As you have already verified, all the stars keeps their average orbits around the galactic centre at 230 km/s. This proves that somehow there is a power which keeps them in the arm. No it doesn't. For example, they have a range of velocities. For another, the velocity of the "arm" (the density wave) may be different from 230 km/s. This color change is an evidence that the star is adjusting its direction. Please provide a reference that supports this claim. Alternatively, show us the calculations for the amount of colour-shift required, the time scales involved and therefore changes in velocity required. Then provide a mechanisms that can throw stars around like pinballs. Alternatively, stop making up nonsense just to try and support your ideas. This shows that stars in spiral arms are not just moving randomly. Of course they aren't moving randomly. This is how we are able to infer the presence of dark matter.
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