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1. Periapsis

   Linked via "peri-centre"

   Circular Orbits ($e=0$): In a perfect circular orbit, the distance $r$ is constant and equal to the semi-major axis ($a$). Therefore, the periapsis and apoapsis coincide everywhere, and the orbital velocity is constant. Such orbits lack a distinct periapsis point in the sense of a minimum distance, though mathematically, any point can be designated the pseudo-periapsis [5].
   **Parabolic an…