Editors of the journal ranked cancer immunotherapy, a type of treatment that pushes the immune system to attack tumors, at the top of their list of scientific achievements this past year.

Data collected by the Fermi Space Telescope provide conclusive evidence that supernovae are the source of the speedy, energetic particles called cosmic rays, an international research team reports.

These charged particles, which are mostly protons, continuously assail the planet from outer space. There is general consensus among scientists that supernova remnants (the leftovers of a supernova explosion) are the sources of cosmic rays, but the final proof has been elusive because cosmic rays are deflected on their way to Earth.