Keeping It Cool: Much Orbit Migration, yet Little Heating, in the Galactic Disk

Abstract

A star in the Milky Way’s disk can now be at a Galactocentric radius quite distant from its birth radius for two reasons: either its orbit has become eccentric through radial heating, which increases its radial action JR (“blurring”), or merely its angular momentum Lz has changed and thereby its guiding radius (“churning”)