Aster shape–motion relationships. (A) Proposed model for how centering MT asters may determine their speed and directionality. Each MT exerts a pulling force on the centrosome that scales to MT length. Aster shape asymmetry, which corresponds to the difference between centrosome position and aster geometrical center, is characterized by a unit vector $e →$ corresponding to aster directionality. Asters migrate with a constant speed determined by the growth rate V_p. Therefore, the aster velocity vector can be simply represented as $V p ⋅ e →$⁠. (B) These shape–motion relationships enable asters to probe local cell geometry to faithfully find the center in any cell shape.