How fast can gas in a young supernova remnant travel?

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Detail of the Cygnus Loop.This nebula is the product of a supernova explosion; in this section, the blast wave has encountered an area of dense interstellar gas, creating turbulence in the wave and causing it to glow. The picture is a composite of three images taken by the Hubble Space Telescope. — Supernova remnant Detail of the Cygnus Loop.
This nebula is the product of a supernova explosion; in this section, the blast wave has encountered an area of dense interstellar gas, creating turbulence in the wave and causing it to glow. The picture is a composite of three images taken by the Hubble Space Telescope.

In young supernova remnants, gas can travel at extremely high velocities. For instance, observations of Supernova 1987A revealed hydrogen lines expanding at 12,000 km per second. Generally, the shells of new supernovae in other galaxies are observed to expand at speeds ranging from 10,000 to 20,000 km per second.1