Prof. Reynolds studies high-energy processes in supernova remnants, active galaxies, and other locales,
in particular the acceleration of particles in strong shock waves. Synchrotron X-ray emission from shell
supernova remnants, originally proposed in 1981, has now been amply confirmed and has become an
important tool for the study of shock acceleration.
Synchrotron X-ray emission is often mixed with thermal X-ray emission from gas shocked to temperatures of 10 MK
and above, and Reynolds has performed observations with various X-ray satellites to study both thermal and
nonthermal processes. Observations with the Chandra X-ray Observatory have led to the firm identification
of the type of Kepler's supernova of 1604 as a thermonuclear (Type Ia) supernova, and to the discovery of the
youngest supernova remnant in the Galaxy, G1.9+0.3, only about 100 years old as observed at Earth.