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#1
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Shapes of Galaxies
I find it interesting that galaxies come in different shapes. I'm
thinking they should all be spiral Just looking at a spiral galaxy you know its rotation that gave it its shape. I can't vision an elliptical galaxy rotating. I can't see its stars being in lock step ether. I read that if two spiral galaxies merged they would form an elliptical galaxy(I don't like that theory) Can't see how an elliptical galaxy would have a central blackhole?? Then we have irregular galaxies,and I have no thoughts regarding them. Like to think "Spin is in" Our Milky Way has spin,and I like that. I see the universe as a big spiral galaxy rotating at 93% of the speed of light. From the outside looking into the universe I see the galaxies,as we see stars in our Milky Way. Bert |
#2
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Shapes of Galaxies
Bert posted:
I'm thinking they should all be spiral Nope, there is no reason they should all be spiral. In the area around our local group of galaxies and other nearby galaxy clusters less than 30 million light years away, about 33 percent of the galaxies observed within that volume are spirals, 13 percent are ellipticals, and 54% are irregulars (often faint dwarf irregulars). Out beyond this distance, the small irregulars get very difficult to detect, so the big bright spirals tend to dominate and the balance of *observed* galaxies shifts a bit in favor of the spirals (even though faint irregular galaxies probably are there too but are too faint to see at the larger distances). However, there is no overriding reason why all galaxies should be spirals. I can't vision an elliptical galaxy rotating. I can't see its stars being in lock step ether. Elliptical galaxies *do* rotate, as is easily seen by looking at the doppler shifts of different portions of them. The stars aren't necessarily "in lock step" with each other, but orbit the center of the galaxy in a wide variety of orbits with all sorts of inclinations and eccentricities. This is why they are the shape that they are. I read that if two spiral galaxies merged they would form an elliptical galaxy(I don't like that theory) Well, its too bad you don't like that theory because there is clear evidence that this happens, mostly with the very large ellipticals which often sit near the center of large clusters of galaxies. Faint halos, rings, and streamers are often seen around these big elliptical galaxies in very long exposure photographs of them, remnants of their original galaxy components after mergers. Computer simulations of colliding spiral galaxies often show them eventually settling down after billions of years into the form of a giant elliptical galaxy. Not all ellipticals form this way, but there is evidence that many of them have formed from galactic mergers. Can't see how an elliptical galaxy would have a central blackhole?? Why would it need one? There are galaxies with central black holes and galaxies without them. Its not a requirement that any galaxy have a black hole at the center. Spiral galaxies show spiral arms not because there is a black hole in the middle, but because of density waves (possibly with the help of magnetic fields) propagating around the disk of the galaxy triggering star formation in the spiral arms. The arms in a spiral galaxy are *not* spiraling-in towards the center of the galaxy, but are rotating around the galaxy just like the stars in them do. Then we have irregular galaxies,and I have no thoughts regarding them. Well, better start thinking about them, because there are a *lot* of them in our universe. -- 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 * ********************************************** |
#3
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Shapes of Galaxies
I don't mean this as an attack, but have you ever heard the expression
"How boring life would be if we were all the same." I feel that hold's true to the universe.......It wouldn't be full of wonder and suprise......... My 2 cent's. Joe |
#4
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Shapes of Galaxies
Hi Joe Just having a little fun. Don't take the universe to seriously
Bert |
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