Evolution of the dimensions (∆x, ∆z) of the supernova remnant evolving into a homogeneous medium with densities 10², 10³, and 10⁴ cm⁻³ (models N2, N3, and N4) in the gravitational field described in Sect. 2. Coloured symbols are for a galactocentric distance r_GC = 4 pc, and lines belong to distances of r_GC = 2 pc (dashed) and r_GC = 6 pc (dotted) for each density (circles for N2, squares for N3, and triangles for N4). Colour denotes the remnant age (0–50 kyr). The grey line is ∆x = ∆z, and the black cross shows the observed dimensions of Sgr A East.