Physics – General Physics
Scientific paper
2009-01-22
Proc.Roy.Soc.Lond.A465:3425-3446,2009
Physics
General Physics
Published in Proc Roy Soc A. A high resolution version of this file can be downloaded from http://papers.rqgravity.net/SpiralS
Scientific paper
10.1098/rspa.2009.0036
We describe the structure and composition of six major stellar streams in a population of 20 574 local stars in the New Hipparcos Reduction with known radial velocities. We find that, once fast moving stars are excluded, almost all stars belong to one of these streams. The results of our investigation have lead us to re-examine the hydrogen maps of the Milky Way, from which we identify the possibility of a symmetric two-armed spiral with half the conventionally accepted pitch angle. We describe a model of spiral arm motions which matches the observed velocities and composition of the six major streams, as well as the observed velocities of the Hyades and Praesepe clusters at the extreme of the Hyades stream. We model stellar orbits as perturbed ellipses aligned at a focus in coordinates rotating at the rate of precession of apocentre. Stars join a spiral arm just before apocentre, follow the arm for more than half an orbit, and leave the arm soon after pericentre. Spiral pattern speed equals the mean rate of precession of apocentre. Spiral arms are shown to be stable configurations of stellar orbits, up to the formation of a bar and/or ring. Pitch angle is directly related to the distribution of orbital eccentricities in a given spiral galaxy. We show how spiral galaxies can evolve to form bars and rings. We show that orbits of gas clouds are stable only in bisymmetric spirals. We conclude that spiral galaxies evolve toward grand design two-armed spirals. We infer from the velocity distributions that the Milky Way evolved into this form about 9 Gyrs ago.
Anderson Erik
Francis Charles
No associations
LandOfFree
Galactic Spiral Structure does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Galactic Spiral Structure, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Galactic Spiral Structure will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-189906