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Accretion Disc Same as a Spiral Galaxy??????
Dave I did not say same,but have some sameness. I think elliptical
galaxies are formed by two spiral galaxies merging. If it makes you feel any better I read it. If a blackhole is in the center of every spiral galaxy,and all blackholes that are devouring a star by creating an accretion in space around them. I see a sameness and to me Jim's pictures gave me this idea. I see lots of my ideas 25 years ago in books I have read just recently. Dave why don't you wait,and read about it. Thinking on your own is just as important than just reading. Now if two spiral galaxies have completely merged with each other,my thoughts are their cores might contain two blackholes revolving around each other,and that means to me some elliptical galaxies have a double core.(so where is the book to throw at me?) Bert |
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Accretion Disc Same as a Spiral Galaxy??????
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Accretion Disc Same as a Spiral Galaxy??????
A spiral galaxy gets its disc shape revolving around a black hole. A
accretion disc gets its shape revolving around a blackhole. Bert |
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Accretion Disc Same as a Spiral Galaxy??????
Bert posted:
A spiral galaxy gets its disc shape revolving around a black hole. No Bert. A spiral galaxy gets its shape from the intital conditions of its formation. The spiral form has NOTHING to do with a black hole being in the middle (many galaxies don't have a central black hole). The spiral arms are thought to be formed by density waves propagating around the galaxy which enhance star formation as the wave moves through the gas. You are confusing some bad artwork of the accretion disk with the form of a spiral galaxy. Accretion disks don't look like spiral galaxies or stuff flowing down the drain. David W. Knisely Prairie Astronomy Club: http://www.prairieastronomyclub.org Hyde Memorial Observatory: http://www.hydeobservatory.info/ ********************************************** * Attend the 10th Annual NEBRASKA STAR PARTY * * July 27-Aug. 1st, 2003, Merritt Reservoir * * http://www.NebraskaStarParty.org * ********************************************** |
#5
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Accretion Disc Same as a Spiral Galaxy??????
"David Knisely" wrote...
in message ... Bert posted: A spiral galaxy gets its disc shape revolving around a black hole. No Bert. A spiral galaxy gets its shape from the intital conditions of its formation. The spiral form has NOTHING to do with a black hole being in the middle (many galaxies don't have a central black hole). The spiral arms are thought to be formed by density waves propagating around the galaxy which enhance star formation as the wave moves through the gas. You are confusing some bad artwork of the accretion disk with the form of a spiral galaxy. Accretion disks don't look like spiral galaxies or stuff flowing down the drain. David W. Knisely Prairie Astronomy Club: http://www.prairieastronomyclub.org Hyde Memorial Observatory: http://www.hydeobservatory.info/ ********************************************** * Attend the 10th Annual NEBRASKA STAR PARTY * * July 27-Aug. 1st, 2003, Merritt Reservoir * * http://www.NebraskaStarParty.org * ********************************************** 'Lo David -- I recently read that scientists are now fairly certain that most, and possibly even all, galaxies have supermassive black holes at their centers... even spherical and oddly shaped galaxies. I agree that accretion disks are different beasts from spiral galaxies (our galaxy is believed to have a tight accretion disk in addition to the billions of stars spiraling around the central black hole), and yet the more i think about it, the more sense it makes that supermassive black holes would be galaxy hubs... and perhaps even bigger and bigger "ultramassive" black holes are at the centers of galaxy clusters and superclusters as well? http://www.mpifr-bonn.mpg.de/div/the...etdisksbh.html This link may also clarify the difference for Herb? Also found this interesting tidbit while searching (it's from nearly two years ago, so you may have already read about it)... http://www.space.com/scienceastronom...le_010913.html happy days and... starry starry nights! -- Kiss the girls and make them cry Just like old Georgie Porgy-- In math base-2 brings Love to mind, Base-10 stirs up an Orgy! Paine Ellsworth |
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Accretion Disc Same as a Spiral Galaxy??????
David K. wrote (responding to Bert):
You are confusing some bad artwork of the accretion disk with the form of a spiral galaxy. Accretion disks don't look like spiral galaxies or stuff flowing down the drain. David, if you were to look at a Seyfert (active core) galaxy's central engine up close, there would be some credance to the "stuff flowing down the drain" pattern. As the inbound material from the accretion disk approaches the BH, it must bifurcate into _two_ flows before riding 'up and over' the central hump, then assume the form of two intake vortices like 'bathtub drains' plunging head-on into the poles of the BH. The essential bipolarity of every (spinning) BH has been discussed a number of times here. A Seyfert galaxy has incandescent superheating material falling in, giving a visual of the actual flow pattern. A quasar in close-up would show a greatly ramped-up version of the same bipolar flow as it was back in the fuel-rich early universe. For some reason the mainstream suffers a block concerning the essential biplarity of BHs and the fact that they _must_ be gravitically bipolar because of their very high spin rate. Bipolar jets are sometimes seen associated with certain massive objects in deep space. Their polar inflows have to be superhot electric plasmas, each generating an enormous magnetic field as it accelerates into the pole, setting up large-scale magnetohydrodynamic (MHD) effects. Slower, lower-energy material in the infall is captured and 'backfired' by the reverse-EMF (reverse-electromotive force) effect (the same principle by which AC induction motors run). The backfired material forms the familiar ejecta plumes or jets, seen shooting out on the polar axis at relativistic speeds. If these bipolar jets aren't the signature of bipolar accretion, I don't know what is. oc |
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Accretion Disc Same as a Spiral Galaxy??????
Hi there. You posted:
I recently read that scientists are now fairly certain that most, and possibly even all, galaxies have supermassive black holes at their centers... even spherical and oddly shaped galaxies. No, many smaller galaxies (especially the irregulars) do not have central supermassive black holes (and in the universe, a majority of galaxies may be such dwarfs). There are undoubtedly black holes in all galaxies, and big ones near the center of many large ones. Some moderate to large galaxies clearly have them (ours has more than one in the nuclear region around the galactic core and possibly one at the very center), but others don't. Some ellipticals which formed from the merger of two large galaxies may have two big black holes in orbits around the eventual center, but may not have one at the precise center. Having a black hole is not a requirement for a galaxy, and certainly is not a requirement for a galaxy to be a spiral, which is where Bert seems to be getting screwed up. Clear skies to you. -- David W. Knisely Prairie Astronomy Club: http://www.prairieastronomyclub.org Hyde Memorial Observatory: http://www.hydeobservatory.info/ ********************************************** * Attend the 10th Annual NEBRASKA STAR PARTY * * July 27-Aug. 1st, 2003, Merritt Reservoir * * http://www.NebraskaStarParty.org * ********************************************** |
#8
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Accretion Disc Same as a Spiral Galaxy??????
David Knisely wrote:
No, many smaller galaxies (especially the irregulars) do not have central supermassive black holes (and in the universe, a majority of galaxies may be such dwarfs). There are undoubtedly black holes in all galaxies, and big ones near the center of many large ones. Some moderate to large galaxies clearly have them (ours has more than one in the nuclear region around the galactic core and possibly one at the very center), but others don't. Some ellipticals which formed from the merger of two large galaxies may have two big black holes in orbits around the eventual center, but may not have one at the precise center. Having a black hole is not a requirement for a galaxy, and certainly is not a requirement for a galaxy to be a spiral, which is where Bert seems to be getting screwed up. Clear skies to you. Note that while the Magellanic Clouds are irregular, and with little if any central condensation or 'disc', they show traces of spiral structure including a faint 'arm' connecting the two. --Odysseus |
#9
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Accretion Disc Same as a Spiral Galaxy??????
Hi Painius Thank you. The link you posted had this to say that goes
with what I posted. "As one considers a galaxy as a giant accretion disk. I think in every direction,and look for sameness. Bert |
#10
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Accretion Disc Same as a Spiral Galaxy??????
Hi David
You wrote, The accretion disk doesn't really show the 3-D "down the drain" effect depicted in some bad TV science shows.... Yeah, I was just trying to point up that if the central engine were examined in extreme close-up, the BH must be gravitically bipolar due to its extreme spin rate- a fact that seems to be lost on the mainstream. They continue to model BH accretion on a 'normal' stellar body's accretion- i.e, a monopolar flow falling "onto" the object instead of a bipolar flow going _into_ its poles. Twin, mirror-imaging "down the drain" vortices _would_ be seen going into the BH's poles. This bipolar flow, sgain, would be apparent only in extreme close-up of the central BH. And bipolar jets, whether powered by MHD effects and a reverse-EMF "shear" I described or some other mechanism, are certainly the signature of bipolar accretion. The just-released story on the millisecond pulsar and gravity waves shows the pulsar to have a high spin rate, though nowhere near as high as a BH's would be. But is spin should be sufficient to show the beginnings of gravitic bipolarity. oc |
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