Cosmic rays are high-energy charged particles, mainly protons, that fly around in space at nearly the speed of light, and bombard the Earth at every moment. Ever since cosmic rays were discovered at the beginning of the twentieth century, scientists have wondered from where they come how they are accelerated. Suzaku’s observations have given us some important clues. One was obtained through the observation of supernova remnant RX J1713-3946, together with the observation with the NASA's Chandra X-ray Observatory. This celestial body emits not only X-rays but also ultrahigh-energy gamma rays, and it’s the gamma rays that attracted our attention.
First, the Chandra X-ray observatory, which has exceptional spatial resolution, captured X-rays whose intensity varied among 2000, 2005 and 2006 observations, namely on time scale of just one year, which is a very short time in astrophysics. , This corresponds to seeing the behavior of charged particles when they are gaining energy (accelerating) and losing energy (cooling). This was the first time we had captured the acceleration phenomena of the cosmic rays directly. On the other hand, Suzaku measured X-ray spectra up 40 keV (kilo electron volt), revealing that X-ray intensities rapidly decrease from near 10 keV. The fact that the X-ray spectra extend up to such a high energy shows that electrons are also accelerated effectively. By combining the observation results of two satellites, it becomes clear that cosmic rays consisting primarily of protons are created and accelerated by means of the shock wave of the supernova remnant.