Download Supernova remnants

Momentum conserving phase
• We shall make a simple analysis of the motion of the shell
• We ignore the internal pressure from the interior hot gas and assume shell moves outwards,
sweeping up matter and conserving momentum (but not energy since it radiates). This is the
snowplough model: high pressure, thin shell
• Since the gas cools so efficiently the shell will be thin and so a single radius R and velocity
dR/dt define its position and dynamics. Momentum conservation demands that:
• Suppose the thin shell is formed
instantaneously at a time t0 when R=R0
and dR/dt = (dR/dt)0. Then:
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