Dr Nigel Maxted’s research is at the intersection of high-energy particle astrophysics and spectral line radio astronomy.
Everyday, the Earth’s atmosphere is bombarded by high-energy particles. These cosmic rays account for 10-25% of the natural human background radiation dose, and at the highest energies the origin is somewhat mysterious. In space, cosmic rays may trigger the chemistry needed to form organic molecules.
Supernovae, the large explosions that mark the end of the lives of high-mass stars are prime suspects in the search for the source of cosmic rays. Supernovae produce magnetised shock waves that can be viewed as shell-like X-ray structures in the sky. When these shock waves collide with giant clouds of space gas, particles can be ‘bounced’ around by magnetic fields and eventually be released into the interstellar medium with a net gain in energy. At this point, they can be travelling close to the speed of light.
The existence of distant populations of cosmic rays can be inferred by observing gamma-rays, which can be produced when cosmic rays interact with gas located near cosmic ray sources. By piecing together gamma-ray observations and radio telescope gas observations, the Galactic particle accelerators that produce the high-energy cosmic rays persistently bombarding our atmosphere can be identified.