Spiral Structure is a result of what is called phase-mixing. This occurs outside of corotation, due to the centre of a perturbed potential travelling faster than the surrounding Interstellar/Intergalactic medium.
These simulations use of either an adaptive mesh, or smoothed-particle hysrodynamics to describe the movement of mass. The luminosity seen here cannot be directly correlated to the real universe and is merely an aid, literally helping us to see where it is. There are infact thought to be thousand of smaller, gravitationally bound structures orbiting the milky-way, just as is seen in this simulation.
Thanks for what appears to be another nicely-done Newtonian n-body simulation.
I think you never get a symmetrical pair of well-formed spiral arms anywhere here in this sequence. I think maybe it's because there's a missing long-wave cosine term provided by quantum gravity waves having a long wavelength consistent with gravitons behaving as if undetectably weak and supposing energy is inversely proportional to wavelength for gravitons too, not just photons.
Spiral arms are outlined by young stars because of waves of star formation, rather than gross density differences in the disc. The density is RELATIVELY constant throughout a disc galaxy, with moving waves of slightly higher density.
"Spiral arms are outlined by young stars because of waves of star formation, rather than gross density differences in the disc"
I'm sure there must be all sorts of seemingly-knowledgable and wonderful-sounding reasons to not attempt the simulations I've suggested, and yours is one of the best, but the simple fact is that they're all incorrect. The arms are simply much brighter and denser than the space between the arms. It's just that simple.
Oh there are density differences don't get me wrong, but the brightness difference is out of proportion to the density difference because the young stars formed in the denser areas don't live long enough to travel far from their points of origin. I dont know if density differences of the magnitude that exist wold show up grossly on a simulation such as this one, or if they change too fast to be readily seen without the outlining stars. Alternately it might require a 'finer-grained' simulation.
I can only guess at this point, but the decay stage for galactic arm evolution is apparently gradual and apparently typically begins with stellar matter lining up in spirals within the ring, while the barrier between the ring and core aquires a wavy characteristic, with a consequent pair of opposed potential drops in the ring plane, allowing two headers of ring matter to penetrate toward the core symmetrically. This much detail I consider a guess.
In the latter stage where the spirals are forming the conditions necessary for the supposed cosine correction are lost and the wave effect is easily phase-spread-swamped away with the loss of ring symmetry and disruption of compact core.
Spiral Structure is a result of what is called phase-mixing. This occurs outside of corotation, due to the centre of a perturbed potential travelling faster than the surrounding Interstellar/Intergalactic medium.
taylrl 1 year ago
These simulations use of either an adaptive mesh, or smoothed-particle hysrodynamics to describe the movement of mass. The luminosity seen here cannot be directly correlated to the real universe and is merely an aid, literally helping us to see where it is. There are infact thought to be thousand of smaller, gravitationally bound structures orbiting the milky-way, just as is seen in this simulation.
taylrl 1 year ago
Thanks for what appears to be another nicely-done Newtonian n-body simulation.
I think you never get a symmetrical pair of well-formed spiral arms anywhere here in this sequence. I think maybe it's because there's a missing long-wave cosine term provided by quantum gravity waves having a long wavelength consistent with gravitons behaving as if undetectably weak and supposing energy is inversely proportional to wavelength for gravitons too, not just photons.
CACBCCCU 2 years ago
Spiral arms are outlined by young stars because of waves of star formation, rather than gross density differences in the disc. The density is RELATIVELY constant throughout a disc galaxy, with moving waves of slightly higher density.
personzorz 2 years ago
"Spiral arms are outlined by young stars because of waves of star formation, rather than gross density differences in the disc"
I'm sure there must be all sorts of seemingly-knowledgable and wonderful-sounding reasons to not attempt the simulations I've suggested, and yours is one of the best, but the simple fact is that they're all incorrect. The arms are simply much brighter and denser than the space between the arms. It's just that simple.
CACBCCCU 2 years ago
Oh there are density differences don't get me wrong, but the brightness difference is out of proportion to the density difference because the young stars formed in the denser areas don't live long enough to travel far from their points of origin. I dont know if density differences of the magnitude that exist wold show up grossly on a simulation such as this one, or if they change too fast to be readily seen without the outlining stars. Alternately it might require a 'finer-grained' simulation.
personzorz 2 years ago
"the brightness difference is out of proportion to the density difference"
I suppose, however the dark area between the arms has significantly less mass than the arms, there are not even any reflective gas nebulae.
CACBCCCU 2 years ago
"has"change to "commonly has"
I can only guess at this point, but the decay stage for galactic arm evolution is apparently gradual and apparently typically begins with stellar matter lining up in spirals within the ring, while the barrier between the ring and core aquires a wavy characteristic, with a consequent pair of opposed potential drops in the ring plane, allowing two headers of ring matter to penetrate toward the core symmetrically. This much detail I consider a guess.
CACBCCCU 2 years ago
In the latter stage where the spirals are forming the conditions necessary for the supposed cosine correction are lost and the wave effect is easily phase-spread-swamped away with the loss of ring symmetry and disruption of compact core.
CACBCCCU 2 years ago
Consider the darkness outside the arms in the barred spiral NGC 1300. This is a fairly nice example of a core and ring decaying into a spiral, IMO.
CACBCCCU 2 years ago
Correct me if I am wrong, but you are proposing that spiral arms are the result of standing gravity waves in a potential well?
personzorz 2 years ago
"you are proposing that spiral arms are the result of standing gravity waves in a potential well?"
Good question. No, I suppose they are a decay stage of the ring. The ring requires a compact dense core symmetry but is disruptive of it.
CACBCCCU 2 years ago
amazing
Qtyled 3 years ago