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Why are most galaxies and solar systems 'flat'?
Why are most galaxies and solar systems 'flat'? If there is a cloud of
dust/gas that starts to coalesce around a localized density in the middle of the dust/gas, it seems it would attract from all 3 dimensions equally. But galaxies and solar systems attract primarily in a single plane. What happened to all the debris above/below the plane? I understand there will probably be an unequal distribution of matter surrounding the central object and there will consequently be a resultant angular momentum after a while. But that doesn't seem to explain why there still isn't debris spiraling in from above/below the primary plane. |
#2
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Why are most galaxies and solar systems 'flat'?
Richard Dickison writted:
: Why are most galaxies and solar systems 'flat'? If there is a cloud of : dust/gas that starts to coalesce around a localized density in the middle of : the dust/gas, it seems it would attract from all 3 dimensions equally. But : galaxies and solar systems attract primarily in a single plane. What : happened to all the debris above/below the plane? : I understand there will probably be an unequal distribution of matter : surrounding the central object and there will consequently be a resultant : angular momentum after a while. But that doesn't seem to explain why there : still isn't debris spiraling in from above/below the primary plane. The trick is to think about what would happen if there were a second plane rotating at an angle to the primary plane. If there were (for the sake of simplicity) two discs, you get interactions between the components of both - collisions, gravitational interactions, etc - until some stable distribution and movement evolved. This stable form would end up as a (more or less) single plane. If you add more discs, you start to get a more realistic picture, but it makes the mathematics and conceptualisation more complicated, and doesn't change the basic idea. You get a similar phenomenon in planets with ring systems - Saturn, Jupiter, Uranus all have multiple rings, but in a single plane. I was watching a film on TV the other night which had a rather nice gas planet with two ring systems intersecting at an angle of around 30 degrees. Very impresive, but hardly likely to be stable... HTH, Gavin |
#3
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Why are most galaxies and solar systems 'flat'?
"Gavin Whittaker" wrote in message ... Richard Dickison writted: [snip] I was watching a film on TV the other night which had a rather nice gas planet with two ring systems intersecting at an angle of around 30 degrees. Very impresive, but hardly likely to be stable... HTH, Gavin Treasure Planet per chance? Disney always took/take a liberty with the laws of science.... |
#4
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Why are most galaxies and solar systems 'flat'?
"Richard Dickison" wrote in message ... Why are most galaxies and solar systems 'flat'? If there is a cloud of dust/gas that starts to coalesce around a localized density in the middle of the dust/gas, it seems it would attract from all 3 dimensions equally. But galaxies and solar systems attract primarily in a single plane. What happened to all the debris above/below the plane? I understand there will probably be an unequal distribution of matter surrounding the central object and there will consequently be a resultant angular momentum after a while. But that doesn't seem to explain why there still isn't debris spiraling in from above/below the primary plane. I also think that Centripatal force would play a part here. Any Galaxy (like ours) that spins around a central point will tend to spread it's mass out along the plane of the spin motion. I understand that calculating the rate a Galaxy turns is one method used to calculate it's mass? Martin |
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Why are most galaxies and solar systems 'flat'?
On Thu, 23 Oct 2003 07:13:03 GMT, "Richard Dickison"
wrote: Why are most galaxies and solar systems 'flat'? If there is a cloud of dust/gas that starts to coalesce around a localized density in the middle of the dust/gas, it seems it would attract from all 3 dimensions equally. But galaxies and solar systems attract primarily in a single plane. What happened to all the debris above/below the plane? I understand there will probably be an unequal distribution of matter surrounding the central object and there will consequently be a resultant angular momentum after a while. But that doesn't seem to explain why there still isn't debris spiraling in from above/below the primary plane. In terms of a Solar System, most of the material that comprises the final Star/Planet system will be hoovered up by the star in the centre of the system. As the cloud shrinks, any rotation in the original cloud will quicken (the skater bringing their arms in trick) and the remaining material will tend to flatten out into a disk around the main body (the star). As the star turns on, any residual material will be vapourised or blown away. Heavier material is harder to blow away than lighter gases which is why the planets nearer the Sun are rocky and the planets further away are gaseous. -- Pete Homepage at http://www.pbl33.co.uk CCD/digicam astronomy |
#6
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Why are most galaxies and solar systems 'flat'?
"Martin" wrote in message ... "Richard Dickison" wrote in message ... Why are most galaxies and solar systems 'flat'? If there is a cloud of dust/gas that starts to coalesce around a localized density in the middle of the dust/gas, it seems it would attract from all 3 dimensions equally. But galaxies and solar systems attract primarily in a single plane. What happened to all the debris above/below the plane? I understand there will probably be an unequal distribution of matter surrounding the central object and there will consequently be a resultant angular momentum after a while. But that doesn't seem to explain why there still isn't debris spiraling in from above/below the primary plane. I also think that Centripatal force would play a part here. Any Galaxy (like ours) that spins around a central point will tend to spread it's mass out along the plane of the spin motion. I understand that calculating the rate a Galaxy turns is one method used to calculate it's mass? Martin Centripetal force would seem to play a part if the debris were being thrown out of the nucleus, but since the nucleus is pulling the debris in, I'm not sure if the intuitive 'water sprinkler' galaxy applies. |
#7
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Why are most galaxies and solar systems 'flat'?
"Richard Dickison" wrote in message ... "Martin" wrote in message ... "Richard Dickison" wrote in message ... Why are most galaxies and solar systems 'flat'? If there is a cloud of dust/gas that starts to coalesce around a localized density in the middle of the dust/gas, it seems it would attract from all 3 dimensions equally. But galaxies and solar systems attract primarily in a single plane. What happened to all the debris above/below the plane? I understand there will probably be an unequal distribution of matter surrounding the central object and there will consequently be a resultant angular momentum after a while. But that doesn't seem to explain why there still isn't debris spiraling in from above/below the primary plane. I also think that Centripatal force would play a part here. Any Galaxy (like ours) that spins around a central point will tend to spread it's mass out along the plane of the spin motion. I understand that calculating the rate a Galaxy turns is one method used to calculate it's mass? Martin Centripetal force would seem to play a part if the debris were being thrown out of the nucleus, but since the nucleus is pulling the debris in, I'm not sure if the intuitive 'water sprinkler' galaxy applies. Is it not a matter of balancing of forces? What the gravitational effect of the nucleus of the galaxy V the centripatal force? Some galaxies spin very slowly (I assume that most spin to a degree?) hence the galaxy will tend to be much more compressed and look less like ours or say Andromeda. Martin |
#8
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Why are most galaxies and solar systems 'flat'?
The link below might be of interest to those reading this thread. Martin http://helios.astro.lsa.umich.edu/Co.../tf_intro.html |
#9
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Why are most galaxies and solar systems 'flat'?
In message , Gavin Whittaker
writes Richard Dickison writted: : Why are most galaxies and solar systems 'flat'? If there is a cloud of : dust/gas that starts to coalesce around a localized density in the middle of : the dust/gas, it seems it would attract from all 3 dimensions equally. But : galaxies and solar systems attract primarily in a single plane. What : happened to all the debris above/below the plane? : I understand there will probably be an unequal distribution of matter : surrounding the central object and there will consequently be a resultant : angular momentum after a while. But that doesn't seem to explain why there : still isn't debris spiraling in from above/below the primary plane. The trick is to think about what would happen if there were a second plane rotating at an angle to the primary plane. If there were (for the sake of simplicity) two discs, you get interactions between the components of both - collisions, gravitational interactions, etc - until some stable distribution and movement evolved. This stable form would end up as a (more or less) single plane. If you add more discs, you start to get a more realistic picture, but it makes the mathematics and conceptualisation more complicated, and doesn't change the basic idea. In which case it seems to me that the interesting question is why some objects are _not_ flat - the Oort Cloud (if it exists), globular clusters, and elliptical galaxies, for instance. You get a similar phenomenon in planets with ring systems - Saturn, Jupiter, Uranus all have multiple rings, but in a single plane. I was watching a film on TV the other night which had a rather nice gas planet with two ring systems intersecting at an angle of around 30 degrees. Very impressive, but hardly likely to be stable... I can't find my copy of Richard Baum's "The Planets: Some Myths and Realities" but ISTR that William Herschel thought he had observed rings around Uranus at right angles ! -- "It is written in mathematical language" Remove spam and invalid from address to reply. |
#10
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Why are most galaxies and solar systems 'flat'?
"Jonathan Silverlight" wrote in message ... In which case it seems to me that the interesting question is why some objects are _not_ flat - the Oort Cloud (if it exists), globular clusters, and elliptical galaxies, for instance. Good point, I guess the interaction between Galaxies, black holes and whatever else we have yet to discover may have big influences on how exactly Galaxies end up the way they do. Martin |
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