Strange Posted March 25, 2017 Posted March 25, 2017 What is wrong with that? I already explained at least two reasons why your extrapolation is probably wrong. Can you please direct me to a relevant article? I provided references. Sorry, it isn't a joke and I really want to know why do you ignore it? I also explained that.
swansont Posted March 25, 2017 Posted March 25, 2017 It is stated clearly: http://iopscience.io...12035/fulltext/ "If we naively increase this by a (Bondi capture) factor of 2.62 to account for the actual mass of the central object, the theoretically predicted accretion rate becomes 10-3 M yr-1." So, based on my understanding the theoretically predicted accretion rate becomes 10-3 M yr-1." What is wrong with that? I don't see any limit for time duration. Do you claim that it is incorrect? Do you claim that our scientists believe that in the past the theoretically predicted accretion rate was lower? Can you please direct me to a relevant article? Our SMBH isn't a baby. It is quite mature man. His age is over 12 billion years and I hope that it can live few more billion years. So one million years in SMBH life time is equivalent to less than one second in our life time. Actually, even if we assume that the SMBH life time is only 12 Billion years and our life time is at least 120 years, than 100 million SMBH life time is equivalent to one year of man life. Therefore: If a man consumes 1500 calories per day (in average), can we assume that it consumes 1500 x 356 calories per year? If our SMBH consumes 10-3 M per year, why can't we assume that it consumes 10-3 M x 1 Million, after one Million years??? Strange's point is that it's a current rate. As the mass of the stars decreases, the rate might change. If new stars are formed or migrate to the area, the rate will change. A million years is a long time. My point (why did you ignore it?) is: so what? It represents a <0.1% increase in the mass of the black hole. I also pointed out that there was other relevant information in the link, including criticism about whether that number is correct, which you are also ignoring.
David Levy Posted March 25, 2017 Author Posted March 25, 2017 (edited) I already explained at least two reasons why your extrapolation is probably wrong. Strange's point is that it's a current rate. Yes, I agree however, when our scientists tried to estimate the age of the universe they have mesured the current rate and set an extrapulation: https://en.wikipedia.org/wiki/Age_of_the_universe "In physical cosmology, the age of the universe is the time elapsed since the Big Bang. Measurements of the cosmic background radiation give the cooling time of the universe since the Big Bang,[3] and measurements of the expansion rate of the universe can be used to calculate its approximate age by extrapolating backwards in time." So, when our scientists are doing excetly the same process in order to verify the whole universe age - that is perfectly OK. No one is asking about the stability of CRM rate over time. However, when I'm using an extrapolation on just a friction of a glaxy life time - it is forbidden. Why? Why if our scientists can extrapolate the whole age of the universe from the current rate, while I can't do a similar process on a friction of a relative time? As the mass of the stars decreases, the rate might change. If new stars are formed or migrate to the area, the rate will change. A million years is a long time. The age of our galaxy is estimated to be over 12 Billion years. One million years is 1/(12 million) than this age. Therefore, we can easily consider that one million years is just a friction of a moment in our galaxy life time. The accretion rate had been set by the radio source, as it is stated clearly: http://iopscience.io...12035/fulltext/ "The radio source Sagittarius A* at the center of our Galaxy is believed to be a 2.6×10 Mblack hole that accretes gas from the winds of nearby stars. " So, if the amplitude of that radio source will decrease than we can estimate a change in the accretion rate. Therefore, we set the rate based on radio source rather than availability of star mass. Our scientists also honestly claim: "is believed" with regards to the idea that the SMBH gets this requested mass from the wind of nearby stars. Hence, I would consider it as an assumption. There is no direct evidence for that. It is one option. In any case, if there is a change in that radio source, we could verify it by monitor other spiral galaxies similar to ours. There are billions of galaxies. We can monitor the radio source at those equivalent galaxies, and get the average accretion rate. This could give us more solid information about the accretion rate. Did we try to do it? Edited March 25, 2017 by David Levy
Strange Posted March 25, 2017 Posted March 25, 2017 Yes, I agree however, when our scientists tried to estimate the age of the universe they have mesured the current rate and set an extrapulation: https://en.wikipedia.org/wiki/Age_of_the_universe "In physical cosmology, the age of the universe is the time elapsed since the Big Bang. Measurements of the cosmic background radiation give the cooling time of the universe since the Big Bang,[3] and measurements of the expansion rate of the universe can be used to calculate its approximate age by extrapolating backwards in time." So, when our scientists are doing excetly the same process in order to verify the whole universe age - that is perfectly OK. Because there are multiple lines of evidence that are consistent with that model. But note that it has been found that simple linear extrapolation does not work because we have found the expansion is accelerating. However, when I'm using an extrapolation on just a friction of a glaxy life time - it is forbidden. Why? Why if our scientists can extrapolate the whole age of the universe from the current rate, while I can't do a similar process on a friction of a relative time? Because you are ignoring other factors, some of which are in the papers you have been quoting. For example, the formation of new stars, the migration of star clusters to the region of the black hole. The accretion rate had been set by the radio source, as it is stated clearly: http://iopscience.io...12035/fulltext/ "The radio source Sagittarius A* at the center of our Galaxy is believed to be a 2.6×10 Mblack hole that accretes gas from the winds of nearby stars. " So, if the amplitude of that radio source will decrease than we can estimate a change in the accretion rate. Therefore, we set the rate based on radio source rather than availability of star mass. As the paper you cited says, the radio emission is consistent with several different models of accretion, based on the star masses around the black hole. Our scientists also honestly claim: "is believed" with regards to the idea that the SMBH gets this requested mass from the wind of nearby stars. Hence, I would consider it as an assumption. There is no direct evidence for that. It is one option. The paper you cited provides the evidence. So it is not an assumption. It is a conclusion derived from several different lines of evidence and theoretical models. What is this thread about? Is it just another "I don't like the conclusions of science and I can't understand the science, therefore it must be wrong." Please grow up. Did we try to do it? Yes.
David Levy Posted March 25, 2017 Author Posted March 25, 2017 (edited) As the paper you cited says, the radio emission is consistent with several different models of accretion, based on the star masses around the black hole. Thanks, Great news! So, the accretion rate is correct and stable. so why it was stated that we can't trust that rate? If it is stable, why we can't multiply it by the no. of years? If one million it too long, what might be consider as an acceptable time frame? Because you are ignoring other factors, some of which are in the papers you have been quoting. For example, the formation of new stars, the migration of star clusters to the region of the black hole. What do you mean by migration of star clusters to the region of the black hole? Please advice which star clusters? With regards to new star formation nearby the SMBH: If the SMBH wants to eat a mass, why he should set any effort in the formation of new stars before he eats them? What is the benefit for the galaxy or the SMBH in this activity? Edited March 25, 2017 by David Levy
swansont Posted March 25, 2017 Posted March 25, 2017 So, the accretion rate is correct and stable. so why it was stated that we can't trust that rate? Where did you get that it was stable over an arbitrary length of time? Why if our scientists can extrapolate the whole age of the universe from the current rate, while I can't do a similar process on a friction of a relative time? Are you doing a similar process? You are doing a linear extrapolation based on a single value.
Strange Posted March 25, 2017 Posted March 25, 2017 So, the accretion rate is correct and stable. so why it was stated that we can't trust that rate? Who says it is stable? Who says it can't be trusted? If it is stable, why we can't multiply it by the no. of years? Even if it were stable, and you multiply it by the number of years, you cannot use that to conclude there should be no stars. Because: 1. New stars are created 2. Stars can migrate to new positions. (Does that sound familiar?) What do you mean by migration of star clusters to the region of the black hole? Please advice which star clusters? http://iopscience.iop.org/article/10.1086/318054/pdf (Does that sound familiar?) With regards to new star formation nearby the SMBH: If the SMBH wants to eat a mass, why he should set any effort in the formation of new stars before he eats them? Black holes don't "want" to do anything. Black holes don't put any effort into the formation of stars. What is the benefit for the galaxy or the SMBH in this activity? Why would there be a benefit?
David Levy Posted March 26, 2017 Author Posted March 26, 2017 (edited) Thanks Strange Do appriciate your support and patience. Who says it is stable? Who says it can't be trusted? Even if it were stable, and you multiply it by the number of years, you cannot use that to conclude there should be no stars. Because: 1. New stars are created 2. Stars can migrate to new positions. http://iopscience.iop.org/article/10.1086/318054/pdf With regards to star migration: In that article dated Jan 2001 there is no evidence for star migration. However, based on mathematical calculation it is believed that stars could migrate inwards. Nice idea - but not solid evidence. Don't forget that some scientists were expecting to see fireworks as G2 approached the SMBH, but this expectation didn't materialized. Do we have any real evidence that S0 stars are drifting inwards? As we trace S2 for quite long time - do we have any idea about its rotation cycle with regards to SMBH location? Is it drifting inwards or outwards? Black holes don't "want" to do anything. Black holes don't put any effort into the formation of stars. Why would there be a benefit? With regards to new star creation: Yes, there must be a benefit. There must be some logic in this new star creation. I can't see any option that the galaxy creates new stars just to eat them when they are still young. Even crocodile mother doesn't eat her young. The total mass in the accretion disk is in the size of an asteroid. That is based on very accurate measurements from many accretion disks at spiral galaxies. I would consider it as the size of the SMBH mouth. So, yes, the SMBH is huge, but somehow its mouth is quite narrow. All it can eat at any given moment is as big as asteroid mass. The sun is bigger by at least 1025 than an asteroid. How could we even consider pushing a star in the size of our sun or even 20 times bigger to this narrow mouth? Can anyone expect the outcome of that? As the SMBH mouth is so narrow, I would consider that it should disassemble any nearby star before he eats it. That actually was the expectation by our scientists as they discussed on a giant star which is been eaten by the SMBH. http://www.einstein-online.info/spotlights/accretion That's also what we do with our food. If we want to eat a stake we cut it to pieces before we push it to our mouth. We normally don't assemble a new cow with our food before we eat it. Therefore, I still wonder why the galaxy generates new stars just to be eaten by the SMBH. I assume that also our scientists understand that it is not feasible for the SMBH to eat the whole star at once. Therefore they offer the idea of "particles wind from nearby stars". Hence, let's focus on this particles wind: Look at our Sun: Do we have any idea what might be the total weight that the sun is losing every year due to this particles wind? I have no data, but I assume that it must be very small portion of the total sun mass. Can we assume that it is no more than 10-25 of the total sun mass? (If you know this data - please correct me). Let's look at the most nearby star - S2. It complete one rotation cycle in more than 15 years. However, it passes close to the SMBH for very short time. Therefore, I assume that as it is close enough, the wind can carry most of those particles to the mouth of the SMBH. However, when it is far away, the wind goes in all directions. How many S0 stars there are in total? Did we try to verify what could be the total particles wind mass from all the nearby stars which the SMBH could get? I can't see any option to gain the total requested mass of 10-3 M which is needed for the SMBH per year just by that particles wind from nearby stars. I would consider a particles wind as a smell. By smelling 1000 apples, would we feel that we eat enough? Edited March 26, 2017 by David Levy
Strange Posted March 26, 2017 Posted March 26, 2017 With regards to star migration: In that article dated Jan 2001 there is no evidence for star migration. However, based on mathematical calculation it is believed that stars could migrate inwards. Nice idea - but not solid evidence. We use mathematics all the time to work out how things will behave: apples falling from trees, the operation of your computer, planets orbiting stars, electric motors in cars, star clusters in galaxies. But feel free to point out the error in their mathematics. On the other hand, if you keep saying "it must be wrong because I am incapable of understanding it" then I will have to report you as a troll. Do we have any real evidence that S0 stars are drifting inwards? Why do you think they are drifting inwards? Yes, there must be a benefit. There must be some logic in this new star creation. I can't see any option that the galaxy creates new stars just to eat them when they are still young.Even crocodile mother doesn't eat her young. I don't know how to respond to a comment as monumentally stupid as this. Do you think apples fall to the ground because the Earth is lonely and they feel sorry for her? The total mass in the accretion disk is in the size of an asteroid. That is based on very accurate measurements from many accretion disks at spiral galaxies. Your source for this mass only mentions the Milky Way's black hole. What is your source for "That is based on very accurate measurements from many accretion disks at spiral galaxies"? Or are you just making stuff up again. I would consider it as the size of the SMBH mouth. So, yes, the SMBH is huge, but somehow its mouth is quite narrow. All it can eat at any given moment is as big as asteroid mass. Nonsense. That is a description of how much mass is currently in the accretion disk. Articles that you have referenced say that in the past, the black hole was more active (had much more mass in its accretion disk). Many galaxies contain active nuclei, with massive accretion disks. So, you have this completely the wrong way round. The amount of "food" available is (currently) limited to the outflow of gas from nearby stars. If more "food" becomes available, then it will fall into the large "mouth". This is only limited by the heat generated by friction as the material falls in which blows some of the material way. Therefore, I still wonder why the galaxy generates new stars just to be eaten by the SMBH. Really? I mean, really?? Do we have any idea what might be the total weight that the sun is losing every year due to this particles wind? I have no data, but I assume that it must be very small portion of the total sun mass. It wouldn't hurt you to do some research: "Thus, the total mass loss each year is about (2–3)×10−14 solar masses,[27] or about one billion kilograms per second. This is equivalent to losing a mass equal to the Earth every 150 million years.[28]" https://en.wikipedia.org/wiki/Solar_wind#Solar_wind_acceleration Did we try to verify what could be the total particles wind mass from all the nearby stars which the SMBH could get? Yes in the paper you cited earlier. But you are now ignoring because you don't like what it says. I can't see any option to gain the total requested mass of 10-3 M which is needed for the SMBH per year just by that particles wind from nearby stars. Please show your calculations, in the same level of detail as those who show that this can happen. I would consider a particles wind as a smell. By smelling 1000 apples, would we feel that we eat enough? I think I will put you back on Ignore, reading this level of stupidity is bad for the health. 2
David Levy Posted March 27, 2017 Author Posted March 27, 2017 (edited) Many galaxies contain active nuclei, with massive accretion disks. Thanks I have no interset in massive accretion disk. Please let me remind you that I'm only focus on inactive nuclei in spiral galaxy. It has a very unique feature - it is a Rotation SMBH. Based on this power, the plasma at the accretion disk is moving almost at the speed of light. However, there is another important force which had been neglected by the science. It is the magnetic field in the plasma matter. http://www.einstein-...ights/accretion "The most efficient mechanism to re-distribute angular momentum involves plasma matter, in which the different particles influence each other via weak magnetic fields. The net result is a redistribution of angular momentum from the inner into the outer regions of the disk. During this process, the matter in the innermost regions manages to shed enough angular momentum to be able to fall onto (or into) the central object itself. In this way, more and more matter accretes onto the central object. Without angular momentum transfer, this growth by accretion would be impossible." So, all the particles in the accretion disk influence each other with weak magnetic field. This magnetic force set a bonding force between each particle with all the others next to it. Therefore, could it be that due to this weak magnetic field, all the particles must move together as a pack? If so, then all of them must accomplish one cycle exactly at the same time. However, the path at the innermost side of the accretion disk is shortest while the path at the outermost side is the longest. Therefore, could it be that the particle at the innermost side moves at the slowest speed, while the one at the outermost moves at the highest speed? We know that all of them are moving almost at the speed of light. However, if the innermost will move inwards, then its speed should decrease and he might fall into the SMBH. However, if the outermost will move further outwards, its speed should increase. This is very critical, as if it gains enough speed, (speed of light?), it might be ejected outwards from the accretion disk. On the other hand, if any particle outside the accretion disk wants to join the pack, it must accomplish one cycle with all the others at the same time. However, as it is further away from the disk its cycle path is much longer than average path on the disk. Hence, in order to achieve it, it must move much faster than a speed of light. This sounds as impossible mission. Therefore, could it be that no particle can join the accretion disk from outside? Could it be that the only option to join the disc is from inside, as we do with our car race track? We use mathematics all the time to work out how things will behave: apples falling from trees, the operation of your computer, planets orbiting stars, electric motors in cars, star clusters in galaxies. But feel free to point out the error in their mathematics. Mathematics is fantastic if we use it correctly. In that mathematic calculation - Did we take care on the rotation force of the Rotatable SMBH in spiral galaxy? Did we take care on the ultra high speed of the particles in the disk? Did we take care on "the different particles influence each other via weak magnetic fields"? Edited March 27, 2017 by David Levy
swansont Posted March 27, 2017 Posted March 27, 2017 So, all the particles in the accretion disk influence each other with weak magnetic field. This magnetic force set a bonding force between each particle with all the others next to it. Show why this should be the case. Therefore, could it be that due to this weak magnetic field, all the particles must move together as a pack? If so, then all of them must accomplish one cycle exactly at the same time. Let's see the math
Strange Posted March 27, 2017 Posted March 27, 2017 Please let me remind you that I'm only focus on inactive nuclei in spiral galaxy. It has a very unique feature - it is a Rotation SMBH. 1. How do you know the black hole is rotating? 2. How do you know this is unique? Based on this power What power? the plasma at the accretion disk is moving almost at the speed of light. Which part of the accretion disk? However, there is another important force which had been neglected by the science. It is the magnetic field in the plasma matter. Why do you think that magnetic fields in plasmas are ignored by science? What do you think plasma physicists do? Why is the very next bit of your post a quotation about magnetic fields in plasmas if these are ignored by science? Can you give one reason why we should not consider this to be trolling? Therefore, could it be that due to this weak magnetic field, all the particles must move together as a pack? A plasma is a fluid. So, no. https://en.wikipedia.org/wiki/Plasma_(physics)#Fluid_model (That page also has a section on the magnetic fields that are being "ignored by science".) We know that all of them are moving almost at the speed of light. Citation needed. This is very critical, as if it gains enough speed, (speed of light?), it might be ejected outwards from the accretion disk. Citation needed. On the other hand, if any particle outside the accretion disk wants to join the pack, it must accomplish one cycle with all the others at the same time. Citation needed. In that mathematic calculation - Did we take care on the rotation force of the Rotatable SMBH in spiral galaxy? Did we take care on the ultra high speed of the particles in the disk? Did we take care on "the different particles influence each other via weak magnetic fields"? As the paper is about plasma in the accretion disk of a supermassive black hole, then I would guess the answer is yes. But please feel free to show the errors in their mathematics. And stop posting random wild guesses about things you don't understand. As you have no interest/ability in learning science, why not go and annoy people on a gardening forum.
David Levy Posted March 29, 2017 Author Posted March 29, 2017 (edited) A plasma is a fluid. So, no. https://en.wikipedia.org/wiki/Plasma_(physics)#Fluid_model There are several types of plasma. At the accretion disk there is Astrophysical plasmas. https://en.wikipedia.org/wiki/Plasma_(physics)#Fluid_model Astrophysical plasmas are also observed in Accretion disks around stars or compact objects like white dwarfs, neutron stars, or black holes in close binary star systems.[30] Plasma is associated with ejection of material in astrophysical jets, which have been observed with accreting black holes[31] or in active galaxies like M87's jet that possibly extends out to 5,000 light-years. https://en.wikipedia.org/wiki/Astrophysical_plasma An astrophysical plasma is a plasma (a highly ionized gas) whose physical properties are studied as part of astrophysics. Much of the baryonic matter of the universe is thought to consist of plasma,[2] a state of matter in which atoms and molecules are so hot, that they have ionized by breaking up into their constituent parts, negatively charged electrons and positively charged ions. Because the particles are charged, they are strongly influenced by electromagnetic forces, that is, by magnetic and electric fields.[citation needed] All astrophysical plasmas are likely influenced by magnetic fields. So, all astrophysical plasmas are likely influenced by magnetic fields. Now let's read again the meaning of magnetic field in that kind of plasma: http://www.einstein-...ights/accretion "The most efficient mechanism to re-distribute angular momentum involves plasma matter, in which the different particles influence each other via weak magnetic fields. It is stated clearly : " the different particles influence each other via weak magnetic fields" Hence, different particles influence each other via weak magnetic fields. However, magnetic field is defined in terms of force on moving charge in the Lorentz force law. http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magfie.html#c1 "The magnetic field B is defined in terms of force on moving charge in the Lorentz force law." Hence, what is the meaning of that magnetic force? Why do you claim that there is no magnetic force between the nearby particles in the accretion plasma? Edited March 29, 2017 by David Levy
swansont Posted March 29, 2017 Posted March 29, 2017 Why do you claim that there is no magnetic force between the nearby particles in the accretion plasma? He didn't. He was rebutting your idea that "all the particles must move together as a pack" This discussion can't move forward if you are going to continually put forth straw man arguments, and make unsubstantiated claims. 1
Strange Posted March 29, 2017 Posted March 29, 2017 So, all astrophysical plasmas are likely influenced by magnetic fields. Which you claimed was ignored by science. Do you want to apologise now or later? Why do you claim that there is no magnetic force between the nearby particles in the accretion plasma? Where did I claim that? It is bad enough that you make up your own physics, but now you are inventing things that people say. 1
David Levy Posted March 30, 2017 Author Posted March 30, 2017 (edited) He didn't. He was rebutting your idea that "all the particles must move together as a pack" Do you want to apologise now or later? Where did I claim that? Sorry if I didn't understand your message correctly. I apologise now. So, do you mean that the message should be? "There is magnetic force between the particles but this force has no effect on the particles, therefore it can't hold them together as a pack". In this case, can you please advice what could be contribution of that magnetic force on the particles? Shall we just ignore it? Edited March 30, 2017 by David Levy 1
Strange Posted March 30, 2017 Posted March 30, 2017 So, do you mean that the message should be? "There is magnetic force between the particles but this force has no effect on the particles, therefore it can't hold them together as a pack". No that isn't what I said, either. Try again. In this case, can you please advice what could be contribution of that magnetic force on the particles? Shall we just ignore it? No. It cannot be ignored. It probably plays a very important role in the behaviour of the plasma.
David Levy Posted March 30, 2017 Author Posted March 30, 2017 (edited) No that isn't what I said, either. Try again. Is it a quiz? I have no clue. So, can it hold them together as some sort of a pack...? No. It cannot be ignored. It probably plays a very important role in the behaviour of the plasma. What do you mean by "very important role"? How does the magnetic force effect the particles? Does it have any effect on the particles rotation around the SMBH? If yes, how? Edited March 30, 2017 by David Levy
swansont Posted March 30, 2017 Posted March 30, 2017 I have no clue. First thing you've gotten right. Maybe you should open a thread asking about the magnetic interaction.
David Levy Posted March 30, 2017 Author Posted March 30, 2017 (edited) With regards to the accretion disk at the Milky Way; Please advice the minimal and the maximal radius of that ring. Edited March 30, 2017 by David Levy
Strange Posted March 30, 2017 Posted March 30, 2017 Is it a quiz? Yes. It is a test of your reading comprehension skills. You have several sources to call on (several of them provided by you). A few clues: 1. A plasma is a FLUID (see previously linked Wikipedia page on plasma) 2. The particles are there because of the GRAVITY of the black hole (see the various linked articles re accretion disks) 3. Because it is a plasma, the behaviour of the particles is affected by the WEAK electric and magnetic fields (see article quoted by you). 4. If the particles were moving together in a solid disk, it would not be a FLUID, it would not be a PLASMA, it would be a SOLID. See if you can put those together. What do you mean by "very important role"? How does the magnetic force effect the particles? Does it have any effect on the particles rotation around the SMBH? If yes, how? Plasma physics is a pretty complex subject about which I know almost nothing. So I could not possibly answer these questions. Some of them may require hundreds of hours of simulation on a supercomputer to answer. Unlike you, I am not going to just make stuff up. With regards to the accretion disk at the Milky Way; Please advice the minimal and the maximal radius of that ring. I don't know. And I don't care.
David Levy Posted March 31, 2017 Author Posted March 31, 2017 (edited) Quote With regards to the accretion disk at the Milky Way; Please advice the minimal and the maximal radius of that ring. I don't know. And I don't care. We should care. It is one of the most important data on the accretion disk. Please try to offer even an estimation. Edited March 31, 2017 by David Levy
Strange Posted March 31, 2017 Posted March 31, 2017 We should care. It is one of the most important data on the accretion disk. And I'm sure people who study such things do care. Please try to offer even an estimation. How would I do that? Maybe search for a paper that attempts to estimate the size: https://arxiv.org/abs/1405.1456
David Levy Posted March 31, 2017 Author Posted March 31, 2017 (edited) Thanks for the article. https://arxiv.org/abs/1405.1456 Please advice if my estimation is correct: It is stated: "The best estimate for the Schwarzschild radius based on observational limits on the black hole mass and distance is 1 RS = 10.2 ± 0.5µas plus systematic errors (Genzel et al. 2010; Falcke & Markoff 2013); we adopt a value of 10 µas for this paper." So, the angular diameter of the SMBH is 1RS, which is estimated as: 1 RS = 10 µas However, in the following article it is stated that it is 37 μas. https://en.wikipedia.org/wiki/Sagittarius_A* Astronomers have been unable to observe Sgr A* in the optical spectrum because of the effect of 25 magnitudes of extinction by dust and gas between the source and Earth.[10] Several teams of researchers have attempted to image Sagittarius A* in the radio spectrum using very-long-baseline interferometry (VLBI).[11] The current highest-resolution measurement, made at a wavelength of 1.3 mm, indicated an angular diameter for the source of 37 μas.[12] At a distance of 26,000 light-years, this yields a diameter of 44 million kilometers. For comparison, Earth is 150 million kilometers from the Sun, and Mercury is 46 million kilometers from the Sun at perihelion. The proper motion of Sgr A* is approximately −2.70 mas per year for the right ascension and −5.6 mas per year for the declination.[13] In any case, let's assume that the diameter of the SMBH is 44 million kilometers (which is almost as the distance from mercury to the Sun). I couldn't find solid data on the accretion disk. It is just stated: " In support of this extrapolation, we note that Meyer et al. (2007) do model accretion disk structure on a scale of a few RS" So, if we assume that 5 might represent "a few", could it be that the diameter of the accretion disk equal to: 5 * 44 Million Km = (about) 200 Million km. Would you consider it as a reasonable estimation? Edited March 31, 2017 by David Levy
Strange Posted March 31, 2017 Posted March 31, 2017 (edited) The 10 µas figure is the angular size of the black hole radius (which would be about 12 million km). The 37 µas figure is the diameter of the radio source - from the accretion disk and/or jets (depending which models are correct). Would you consider it as a reasonable estimation? I have no idea. The Meyer et al. 2007 paper is here: http://www.aanda.org/articles/aa/abs/2007/39/aa8009-07/aa8009-07.html There is also the added complexity that a black hole appears larger than it is (due to gravitational lensing). I think this doubles the apparent size of the black hole. More here: http://www.eventhorizontelescope.org/science/physical_models.html Edited March 31, 2017 by Strange
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