Supernova remnant

Supernova remnant




Perhaps the most famous and best-observed young SNR was formed by SN 1987A, a supernova in the Large Magellanic Cloud that was discovered in 1987. Other well-known, older, supernova remnants include Tycho (SN 1572), a remnant named after Tycho Brahe, who recorded the brightness of its original explosion (AD 1572) and Kepler (SN 1604), named after Johannes Kepler. The most recent remnant in our galaxy is G1.9+0.3, discovered in the galactic center and estimated to have gone supernova 140 years ago.

Summary of stages

An SNR passes through the following stages as it expands:

  2. Sweeping up of a shell of shocked circumstellar and interstellar gas. This begins the Sedov-Taylor phase, which can be well modeled by a self-similar analytic solution. Strong X-ray emission traces the strong shock waves and hot shocked gas.
  4. Cooling of the interior. The dense shell continues to expand from its own momentum, in a momentum-driven snowplow. This stage is best seen in the radio emission from neutral hydrogen atoms.
  5. Merging with the surrounding interstellar medium. When the supernova remnant slows to the speed of the random velocities in the surrounding medium, after roughly a million years, it will merge into the general turbulent flow, contributing its remaining kinetic energy to the turbulence.

Types of supernova remnant

There are three types of supernova remnant:

  • Shell-like, such as Cassiopeia A

Origin of cosmic rays

Supernova remnants are the major source of Galactic cosmic rays. The connection between cosmic rays and supernova remnants was first suggested by Walter Baade and Fritz Zwicky in 1934. It was shown to be consistent with the cosmic ray losses of the Milky Way if the efficiency of acceleration is about 10 percent by Vitaly Ginzburg and Sergei Syrovatskii in 1964, and it is supported by a specific mechanism called "shock wave acceleration" based on Enrico Fermi's ideas, which is still under development.


Supernova remnants can provide the energetic shock fronts required to generate ultra-high energy cosmic rays. Observation of the SN 1006 remnant in the X-ray has shown synchrotron emission consistent with it being a source of cosmic rays. However, for energies higher than about 1015 eV a different mechanism is required as supernova remnants cannot provide sufficient energy.

See also


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