Radial migration of the Sun in the Milky Way: a statistical study

The determination of the birth radius of the Sun is important to understand the evolution and consequent disruption of the Sun's birth cluster in the Galaxy. Motivated by this fact, we study the motion of the Sun in the Milky Way during the last 4.6 Gyr in order to find its birth radius. We carried out orbit integrations backward in time using an analytical model of the Galaxy which includes the contribution of spiral arms and a central bar. We took into account the uncertainty in the parameters of the Milky Way potential as well as the uncertainty in the present-day position and velocity of the Sun. We find that in general, the Sun has not migrated from its birth place to its current position in the Galaxy (R-circle dot). However, significant radial migration of the Sun is possible (1) when the 2: 1 outer Lindblad resonance of the bar is separated from the corotation resonance of spiral arms by a distance similar to 1 kpc, and (2) when these two resonances are at the same Galactocentric position and further than the solar radius. In both cases, the migration of the Sun is from outer regions of the Galactic disc to R-circle dot, placing the Sun's birth radius at around 11 kpc. We find that in general, it is unlikely that the Sun has migrated significantly from the inner regions of the Galactic disc to R-circle dot.