Galactic bar orbits
Galactic bars, resonances and stellar migration
Sandbox Physics ·
Stars orbit through patterns that can rotate at a different speed. Begin with that picture, derive frequencies and angular-momentum exchange, then solve complete orbits and examine how evolving patterns move stars.
L1
Why stars pass through galactic spiral arms
A spiral is a changing pattern of stars and gas. Follow how differential rotation, orbital resonances and temporary arms separate a pattern from its stars.
L1
Differential rotation and orbital resonances
Derive angular and epicycle frequencies for a flat rotation curve, then locate corotation and the circular Lindblad reference radii.
L2
Torque and energy in a rotating bar
Derive the Jacobi integral from specific torque and power, then identify the extra work when a bar grows or changes its pattern speed.
L3
Periodic orbits and radial migration
Shoot complete periodic parents in one fixed bar, distinguish linear stability from orbital shape, and follow how temporary waves can leave migration.
L3
Recalculate a bar orbit from saved states
Run independent Python integration, analyze saved angular momentum and torque, shoot six periodic parents, and reproduce the registered failure examples.
L4
Reading the 2026 bar-resonance tree rings
Read Chiba et al. 2604.01294v1 from its live/static-halo control to phase-space ordering, satellite tests and conditional pattern-speed recovery.
Sources and calculation scope
- Dehnen (1999v1/2000), The Effect of the Outer Lindblad Resonance of the Galactic Bar on the Local Stellar Velocity Distribution
Fixed 14-page astro-ph/9911161v1, all text read in parameter preflight; equation 3, section 3 and original orbital figures. The own model uses a fixed bar radius 0.5 and counterclockwise convention. The paper's historical Milky Way inference is not treated as a current measurement.
- Sellwood & Binney (2002), Radial mixing in galactic discs, astro-ph/0203510v2
Fixed 13-page v2, complete original read; section 2 specific energy/action exchange and sections 3–4 transient self-gravitating waves. The paper's live-disk simulations are distinct from our prescribed external-bar release.
- Chiba, Fujii, Baba, Dubinski & Schönrich (2026), Tree-ring structure of Galactic bar resonance in N-body simulations, arXiv:2604.01294v1
Fixed 1 April 2026 v1, PDF draft dated 3 April; complete 21 pages including appendices/references actually read. Key printed pages 3/5/6/7/8/10/13/15/18 rendered and viewed. A/B live/static control, C/D satellite tests, equations 5–11 and appendices A–D; no original PDF/figure is redistributed.
- Sandbox Physics independent galactic-bar scientific reader v1
Own zero-network Python integration and saved-record analysis: one full 256-tracer population, ten independent DOP853 controls, exact circle/epicycle, prescribed-growth work, six fresh periodic roots and three own synthetic figures. No App, completed orbit input, original paper or observed data.