David Kaplan's research concerns multi-wavelength (radio, infrared, optical, X-ray) observations of a variety of types of young neutron stars such as isolated, thermally emitting neutron stars and magnetars. He is also working on detecting radio transients with the Murchison Widefield Array, the Australia Square Kilometer Array Pathfinder and other facilities.
|MWA Antenna tile with 16 dipoles placed on a ground screen of 5x5m||UWM Adjunct Prof. Luis Anchordoqui and Prof. Subir Sarkar from Oxford University installing Auger detector electronics during a shift.
Ultra-high energy cosmic rays (UHECRs) are extremely energetic subatomic particles (mostly protons, but also some heavier atomic nuclei) with energies greater than 1018.5 eV. Currently it is only possible to observe UHECRs through the cosmic ray showers produced as they interact with the Earth's atmosphere. This indirect method of observation is required due to the extremely low numbers of incident cosmic rays at these energies (about 1 particle/km2/sr/yr). The Pierre Auger Observatory is the most advanced ground-based experiment to detect extensive air showers, which spread over several kilometres. The Observatory consists of both Cherenkov detectors monitoring several large tanks of water for light produced by high-energy particles, and fluorescence detectors used to track the glow of the primary particle as it descends through the atmosphere.
At the high end of the spectrum the flux reduces to about 1 particle/km2/sr/millennium! This challenging extreme energy region is the scope of the Extreme Universe Space Observatory (EUSO) attached to the Japanese Experiment Module (JEM) on board the International Space Station (ISS). JEM-EUSO is an innovative pathfinder space mission that will orbit the Earth every 90 minutes recording video clips of fast UV flashes by sensing the fluorescence light produced through charged particle interactions.
The origin of UHECRs remains a mystery, as does the mechanism to accelerate particles to these energies. However, the particles have enough energy to escape the typical magnetic field of a spiral galaxy, and most astronomers believe that UHECRs are of extragalactic origin. Possible sources include active galactic nuclei, dormant quasars with associated supermassive black holes, and galaxy mergers.