  It is thought that Galactic cosmic ray (CR) nuclei are gradually accelerated
to high energies (up to ~300 TeV/nucleon, where 1TeV=10^12eV) in the expanding
shock-waves connected with the remnants of powerful supernova explosions.
However, this conjecture has eluded direct observational confirmation^1,2 since
it was first proposed in 1953 (ref. 3). Enomoto et al.^4 claim to have finally
found definitive evidence that corroborates this model, proposing that the
very-high-energy, TeV-range, gamma-rays from the supernova remnant (SNR) RX
J1713.7-3946 are due to the interactions of energetic nuclei in this region.
Here we argue that their claim is not supported by the existing multiwavelength
spectrum of this source. The search for the origin(s) of Galactic cosmic ray
nuclei may be closing in on the long-suspected supernova-remnant sources, but
it is not yet over.
