What We Found:
Using NASA's Chandra X-ray Observatory, the team obtained multi-epoch x-ray images with high spatial resolution (1 arcsec) aiming at measuring the proper motion of the SNR shell. Chandra images taken in 2000, 2005, and 2006 were compared to derive the proper motion (and therefore the speed of the shock), which in turn gives us an age estimate for this remarkable supernova remnant. Surprisingly, the team found temporal variability in the x-ray strength of compact features from 2000 to 2005, and also from 2005 to 2006 (Fig. 2). The year-scale variability indicates that we have witnessed, for the first time, the "real time" production of cosmic rays in the supernova shell. Moreover, the variability is observational evidence in support of the substantial amplification of the magnetic field in the shock of the supernova remnant. In fact, the amplification of the magnetic field is a key ingredient of the theory
of cosmic-ray acceleration, and has recently been predicted theoretically (though the microscopic physical processes have yet to be explored). Independently, the team used a new hard x-ray detector on the Japanese Suzaku satellite in order to measure the wide-band x-ray spectrum up to 40 keV (Fig. 3). The spectroscopic measurements revealed that the x-ray intensity falls rapidly above 5 keV--a
spectral cutoff. Modeling the position of the cutoff by the acceleration theory indicates that the acceleration takes place in extremely tangled magnetic fields that allow particles to be scattered and accelerated in the most effective way. The new findings provided by the Chandra and Suzaku data led the team to conclude that protons can be accelerated in the SNR shock front to energies at least of the order of 1 PeV, thus capable of accounting for the cosmic rays arriving at Earth.