What physical condition defines the transition into the Sedov-Taylor Phase?
The blast wave begins spending kinetic energy on accelerating and heating the captured surrounding interstellar material.
The Sedov-Taylor phase marks the stage where the remnant transitions from unchecked expansion to dynamic interaction with the environment. This transition occurs when the outward-moving blast wave starts sweeping up significant quantities of the ambient interstellar medium (ISM). The energy from the blast wave is then actively converted into accelerating and heating this captured material. This process leads to the characteristic feature of this middle-aged phase: the interior gas being adiabatically heated to extremely high temperatures, reaching millions of degrees Kelvin, and resulting in a more organized spherical or shell-like structure.
